- Email: [email protected]
Why does carbon increase in highly weathered soil under no-till upon lime and gypsum use?
Science of the Total Environment 599–600 (2017) 523–532
Contents lists available at ScienceDirect
Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv
Why does carbon increase in highly weathered soil under no-till upon lime and gypsum use? Thiago Massao Inagaki a, João Carlos de Moraes Sá b,⁎, Eduardo Fávero Caires b, Daniel Ruiz Potma Gonçalves b a b
Technical University of Munich, Chair of Soil Science, Institute for Advanced Study, Email-Ramann Str. 2, 85354 Freising, Bayern, Germany Department of Soil Science and Agricultural Engineering, State University of Ponta Grossa, Av. Carlos Cavalcanti 4748, Campus de Uvaranas, 84030-900, Ponta Grossa, Paraná, Brazil
H I G H L I G H T S
G R A P H I C A L
A B S T R A C T
• Lime and gypsum use in field and incubation experiments increases soil C. • Increase of calcium content and soil biological activity resulted in SOC gains. • Calcium and labile SOC formed complex with mineral soil fractions. • Associations between calcium and labile SOC can be the pathway to increase C sequestration.
a r t i c l e
i n f o
Article history: Received 26 January 2017 Received in revised form 24 April 2017 Accepted 29 April 2017 Available online xxxx Editor: Ajit Sarmah Keywords: Carbon sequestration Soil biology Acid soils Soil organic matter Soil correction Incubation
a b s t r a c t Field experiments have been used to explain how soil organic carbon (SOC) dynamics is affected by lime and gypsum applications, however, how SOC storage occurs is still debatable. We hypothesized that although many studies conclude that Ca-based soil amendments such as lime and gypsum may lead to SOC depletion due to the enhancement of microbial activity, the same does not occur under conservation agriculture conditions. Thus, the objective of this study was to elucidate the effects of lime and gypsum applications on soil microbial activity and SOC stocks in a no-till field and in a laboratory incubation study simulating no-till conditions. The field experiment was established in 1998 in a clayey Oxisol in southern Brazil following a completely randomized blocks design with a split-plot arrangement and three replications. Lime and gypsum were surface applied in 1998 and reapplied in 2013. Undisturbed soil samples were collected before the treatments reapplications, and one year after. The incubation experiment was carried out during 16 months using these samples adding crop residues on the soil surface to simulate no-till field conditions. Lime and gypsum applications significantly increased the labile SOC stocks, microbial activity and soil fertility attributes in both field and laboratory experiments. Although the microbial activity was increased, no depletion of SOC stocks was observed in both experiments. Positive correlations were observed between microbial activity increase and SOC gains. Labile SOC and Ca2+ content increase leads to forming complex with mineral soil fractions. Gypsum applications performed a higher influence on labile SOC pools in the field than in the laboratory experiment, which may be related to the presence of active root system in the soil profile. We conclude that incubation experiments using lime and gypsum in undisturbed samples confirm that soil microbial activity increase does not deplete SOC stocks under conservation agriculture. © 2017 Elsevier B.V. All rights reserved.
Abbreviations: SOC, Soil organic carbon; SL, Surface applied lime; HWEOC, Hot-water extractable organic C; POXC, Permanganate oxidizable organic carbon; TOC, Total organic carbon. ⁎ Corresponding author. E-mail address: [email protected] (J.C. de Moraes Sá).
http://dx.doi.org/10.1016/j.scitotenv.2017.04.234 0048-9697/© 2017 Elsevier B.V. All rights reserved.
524
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
1. Introduction The use of lime on agriculture has been reported as an effective practice to control soil acidity and minimize the toxicity of Al3+, mainly in tropical and subtropical environments. Gypsum has also been recognized by its efficiency to reduce the Al3+ toxicity in deeper layers and contents (Caires et al., 2015). Although the to increase Ca2+ and SO2− 4 influence of both practices, especially lime, on soil organic carbon (SOC) dynamics has been intensively discussed, the factors and processes which govern their increases or decreases are not fully understood (Paradelo et al., 2015). Reports indicating increase (Briedis et al., 2012a, 2012b), decreases (Chan and Heenan, 1999; Fuentes et al., 2006; Aye et al., 2016) and no effect (Wyngaard et al., 2012) of lime applications on SOC stocks demonstrate the influence of several drivers such as climate, soil texture, soil management and biomass input. Gypsum effects on SOC although less studied than lime have demonstrated a significant effect to promote carbon sequestration, as demonstrated by Araújo (2016) in sugarcane fields and Inagaki et al. (2016) in long-term no-till field. Higher biomass inputs from crop residues in soils resulting from the lime and gypsum applications have been pointed out as the main source of SOC increases in soils (Briedis et al., 2012a; Inagaki et al., 2016). In addition, the presence of Ca2 + ions are recognized to work as an ionic bridge between soil organic matter and clay particles, increasing soil aggregation and providing C protection (Briedis et al., 2012b). The increase of biomass input and the aggregating mechanisms of Ca2 + in soils work to increase carbon sequestration in long-term experiments when associated with conservation agriculture. In contrast, soil disturbance and low biomass input stand out as the main reasons for SOC depletions in liming experiments (Caires et al., 2006; Yagi et al., 2014; Aye et al., 2016). In a recent study, Aye et al. (2016) reported reduction of SOC stocks in long-term liming experiments, citing the fields low Cbiomass inputs as the main reason for this depletion. According to the authors, the crop residue input was not enough to compensate the higher SOC mineralization caused by lime addition. Incubation experiments in soils have been widely used, mainly because of their capacity to create ideal experimental conditions, eliminating interference of humidity and temperature on soil microbial activity (Curtin et al., 2012). However, incubation experiments performed to assess the lime and gypsum influence on SOC usually make use of disturbed samples with no crop residue addition (Fuentes et al., 2006; Wong et al., 2009), which commonly results in SOC depletion as a consequence of the microbial biomass activity increase. Therefore, the use of new methods to evaluate the lime and gypsum activity in laboratory studies is necessary to better understand its influence on SOC dynamics in conservation agriculture conditions. We hypothesized that although many studies conclude that Cabased soil amendments such as lime and gypsum may lead to SOC depletion due to the enhancement of microbial activity, the same does not occur under conservation agriculture conditions. Thus, the objective of this study was to evaluate the effects of lime and gypsum applications on SOC pools, microbial activity and soil fertility in a notill field and in a pilot incubation experiment using undisturbed soil with crop residue additions to simulate conservation agriculture conditions. 2. Material and methods 2.1. Site description and soil The experiment was performed in a no-till crop field area in Ponta Grossa PR, southern Brazil (25°10′S, 50°05′W). The annual precipitation is approximately 1550 mm with average maximum and minimum temperatures of 22 and 13 °C, respectively. According to Köppen–Geiger System (Peel et al., 2007), the climate is described as Cfb type (mesothermal, humid, subtropical), with mild summer and frequent
frosts during the winter. The average altitude is 970 m above sea level. The soil is classified as red Latosol (Brazilian classification, Embrapa (2013)) equivalent to a clayey, kaolinitic, thermic Rhodic Hapludox (Soil Survey Staff, 2010), with 610 g kg−1 of clay. 2.2. Soil sampling and field experimental design The experimental area was previously used as a pastureland with no historical of lime and gypsum applications. In 1998, the lime and gypsum experiment was established in a completely randomized design with three replicates. The plots sizes were 224 m2 (32 × 7 m) and the subplots sizes were 56 m2 (8 × 7 m). In the main plots, the treatments were assigned as follow: 1) control, no lime application; and 2) Surface lime application (SL) of 4.5 Mg ha− 1, divided in three yearly applications of 1.5 Mg ha− 1 from the establishment of the experiment (Fig. 1). The lime rate was calculated to raise the base saturation in the topsoil (0–20 cm) to 70%. In the subplots, four rates of gypsum were surface-applied: 0, 3, 6, and 9 Mg ha− 1. Further information about the experimental site was described by Inagaki et al. (2016). In 2013, the lime treatment was reapplied in a full surface application of 4 Mg ha−1. Gypsum treatments were also reapplied on soil surface at the same rates of 0, 3, 6 and 9 Mg ha−1. Soil samples were collected in August 2013 at the depths of 0–0.05, 0.05–0.10, 0.10–0.20, 0.20–0.40 and 0.40–0.60 m before the lime and gypsum reapplications, and in August 2014, one year after. During the crop season, the soil was cultivated with soybean crop (Glycine max) during the summer and let under fallow during the winter. All the soil analyses were performed in both years to calculate the short-term gains. 4.5, 20 and 37 kg ha−1 of NPK at sowing in band application were used in the area for soybean crop. 2.3. Pilot incubation experiment For this experiment, we have developed a pilot incubation trial using undisturbed soil samples with addition of crop residues on soil surface, in order to mimic the conditions of a no-till field. No study, in our knowledge, has examined the lime and gypsum effects under these conditions. We collected 24 undisturbed samples (5 × 5 cm steel rings) randomly from a control plot (i.e. no lime and no gypsum application) in the 0–0.05 m layer in 2013. The experimental design used was completely randomized with factorial 2 × 4, with three replicates. The factors evaluated in the experiment were: a) two liming treatments: Control (no lime) and surface lime application of a rate equivalent to 4 Mg ha−1; and b) Gypsum applied in the rates equivalent to 0, 3, 6 and 9 Mg ha−1 (Fig. 2). The rates were the same applied on the field experiment. Both lime and gypsum treatments were manually applied over the top of each undisturbed sample. Before the samples incubation, we added an equivalent of 10 Mg ha−1 of maize residues (Zea mays – 448 g kg− 1 of C content) on the surface of each sample in order to simulate the C-biomass input in no-till system. Twelve months after, we added the equivalent of 4 Mg ha−1 of soybean residue (Glycine max – 389 g kg−1 of C content), simulating a corn-soybean crop rotation. The samples were inside of hermetic closed glass flasks, maintained in a dark chamber under controlled temperature of 28 °C ± 2 °C, and approximately on 50% of the maximum water retention capacity. Samples moisture was maintained constant through water weekly additions. After 480 days of incubation (16 months), the remaining crop residues were manually removed from the surface and the soil was collected, dried under 40 °C and passed by a 2 mm sieve. 2.4. Soil basal respiration The determination of soil basal respiration followed the methodology described by Jenkinson and Powlson (1976). Briefly, each
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
525
Fig. 1. Chronology of the experimental design from 1980 to 2014. Adapted from Inagaki et al. (2016).
undisturbed soil sample was maintained in a 1 L glass flask sealed with a beaker containing 1 M NaOH solution used to capture the CO2 emitted by the sample. Then, a titration with the excess of NaOH was performed with HCl solution 0.5 M and phenolphthalein as an indicator. Flasks incubated only with the NaOH solution were used as blank to correct the results. During the incubation period, basal respiration was measured in two phases: 1st phase - addition maize residues (0–12 months incubation): determinations at 2, 4, 6, 8, 10, 16, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330 and 360 days from the start of incubation. 2nd Phase addition of soybean residues (12 to 16 months): the determinations 362, 364, 366, 368, 370, 372, 376, 390, 420, 450 and 480 days from the start of incubation. In each measurement, the NaOH solutions were replaced in each flask.
2.6. Permanganate oxidizable organic carbon (POXC) The method for SOC extraction by potassium permanganate (KMnO4) was adapted from the studies of Tirol-Padre and Ladha (2004) and Culman et al. (2012). For the SOC extraction, a 0.06 M KMnO4 solution was applied into 1.5 g of soil in a 15 mL centrifuge tube. After the extraction and centrifuging, the supernatant was pipetted into an Erlenmeyer and diluted with deionized water. The extracted SOC was then measured with a spectrometer in 565 nm of absorbance. A standard curve was performed with pre-determined concentrations of KMnO4 solutions and the SOC content of the samples was calculated based in the relationship Absorbance × KMnO4 concentration. 2.7. Total soil organic carbon and nitrogen contents
2.5. Hot water extractable organic C (HWEOC) The determination of the SOC content extracted by hot water was conducted according to the methodology described by Ghani et al. (2003). Briefly, we weighed 1.5 g of soil for each sample in 15 mL centrifuge tubes. The samples were then maintained at 80 °C for 16 h in deionized water. After the extraction with hot water, the samples were centrifuged, the supernatant was pipetted into an Erlenmeyer flask and the content of C was determined by wet combustion, using the Walkley Black method (Nelson and Sommers, 1996), through oxidation by potassium dichromate and titration with ferrous ammonium sulfate.
The contents of total SOC and N was performed by dry combustion with an elementary CN analyzer (TruSpec CN, LECO, St. Joseph, MI, USA). According to de Moraes Sá et al. (2013), the carbonates content of Oxisols and Cambisols of the region are insignificant (b0.25% of the SOC content). For this reason, we considered that the C determined by dry combustion represent the total SOC content of this soil. 2.8. Soil fertility attributes Soil pH was determined in a 0.01 M CaCl2 suspension. The contents of exchangeable Ca, Mg and Al were extracted with a 1 M KCl solution
526
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
Fig. 2. Arrangement of the laboratory incubation experiment following a completely randomized design with three replicates. Four gypsum rates (0, 3, 6 and 9 Mg ha−1) with and without lime application (4 Mg ha−1) were used as treatments. The total incubation period was 16 months. 10 Mg ha−1 of corn and 4 Mg ha−1 of soybean residues were added on the soil surface of all samples at 0 and 12 months of the incubation period to simulate no-till conditions.
and determined by Atomic absorption spectroscopy, and exchangeable K+ by flame photometry according to the procedures described by Pavan et al. (1992).
3. Results
2.9. SOC stocks calculation
One year after the lime and gypsum reapplications in the field experiment, we found significant gains in soil fertility, SOC pools and biological (i.e., enzyme) activity compared with the values found in the previous year (Table 1). Although the soil quality was improved by both treatments, the soybean crop yield was not affected, and no interaction between the two Ca-based soil amendments were found overall. Lime applications significantly decreased the Al3 + contents in deeper layers (20–40 and 40–60 cm), increased the Ca2 + content all along the soil profile, the pH at topsoil, and promoted Mg2+ leaching (Table 2). Similarly, gypsum significantly decreased Al3+ and increased the Ca2+ and Mg2+ content in deeper layers, but it did not change soil pH (Table 1). At the laboratory incubation experiment, significant increases in the Ca2+ content were also observed due to the application of lime and gypsum. Soybean crop productivity ranged from 4.2 Mg ha−1 (i.e. no lime, no gypsum) to 4.7 Mg ha−1 (i.e. SL + 9 G) (data not shown). However, no significant effect of Ca-based soil amendments applications was found.
The calculus for SOC stocks in each layer and in each SOC pool were performed by the following equation:
−1 SOC stock Mg ha −1 SOC content g kg Soil bulk density Mg m−3 depth ðcmÞ ¼ 10
2.10. Statistical analysis The lime and gypsum treatments were analyzed by analysis of variance (ANOVA) using the software SISVAR (Ferreira, 2008). The means of lime treatments were compared using LSD test at p = 0.05. Analysis of simple linear regression were performed using the software R (R Development Core Team, 2014). The criterion for choosing the model was the magnitude of the determination coefficients significant at p b 0.05. A discriminant analysis of principal components was carried out in this study to observe the separation between limed and non-limed plots and the relationship among the soil fertility, crop productivity, biological activity and SOC pools in the field and laboratory experiment. The package ade4 of R software was used in this study (R Development Core Team, 2014).
3.1. Effects of lime and gypsum on soil fertility attributes and crop productivity in field experiment
3.2. Effects of lime and gypsum on SOC pools and biological attributes Increases in the stocks of SOC pools and soil biological attributes due to lime and gypsum applications were observed either in the field as in the laboratory incubation experiments. Control plots presented insignificant changes in the evaluated variables from the year before the lime and gypsum reapplications, and no losses of SOC or biological activity was observed. In the incubation experiment, lime and gypsum treatments significantly increased the stocks of SOC pools, soil respiration
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
527
Table 1 Analysis of variance for field gains and laboratory incubation study. Soil depth cm
0–5
5–10
10–20
20–40
40–60
0–60
Variation Source
Soybean Crop yield
Lime Gypsum Lime × Gypsum Lime Gypsum Lime × Gypsum Lime Gypsum Lime × Gypsum Lime Gypsum Lime × Gypsum Lime Gypsum Lime × Gypsum Lime Gypsum Lime × Gypsum Lime Gypsum Lime × Gypsum
ns ns ns
Field experiment
Laboratory incubation study
HWEOC
POXC
SOC
β-glycosidase
Al
Ca+2
Mg
K
pH
HWEOC
POXC
RESP
SOC
TN
Ca+2
* ** ns ** ** ns ** ** ns ns ns ns ns ns ns * * ns
* * ns * * ns * * ns ns ns ns ns ns ns * * ns
ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns
** * ns ** ** ns ns ns ns ns ns ns ns ns ns – – –
ns ns ns ns ns ns ns ns ns * ns ns * * ns – – –
** L** ns * ns ns * ns ns * L* ns ** L* * – – –
** * ns * ns ns ns ns ns * * ns * ** ** – – –
ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns – – –
* ns ns * ns ns ns ns ns ns ns ns ns ns ns – – –
** L** ns – – – – – – – – – – – – – – –
** L* ns – – – – – – – – – – – – – – –
** L* ns – – – – – – – – – – – – – – –
ns ns ns – – – – – – – – – – – – – – –
ns ns ns – – – – – – – – – – – – – – –
** L** ns
ns = not significant; ** = Significant at p b 0.01; * = Significant at p b 0.05; – = not applicable. HWEOC: hot water extractable organic carbon; POXC: permanganate oxidizable organic carbon; TOC: total organic carbon; TN: Total Nitrogen; RESP: Soil Basal Respiration; L: Linear function.
and Ca2+ content. The total SOC and N stocks stayed in the same level and no interaction was observed between lime and gypsum treatments. At the discriminant analysis of principal components for the field experiment, we can observe a close relationship between soil fertility attributes, SOC pools, β-glycosidase activity and soybean crop productivity in the 1st principal component, which explained 69% of the experiment variation (Fig. 3). Limed and control plots were clearly separated by the first discriminant axis, showing higher levels of SOC accumulation efficiency and lower Al+3 contents. We can also observe a separation between gypsum rates by the 1st discriminant function. The gypsum treatments presented the following sequence of SOC accumulation efficiency: 0G N 3G N 6G N 9G (i.e. G = gypsum rate in Mg ha−1). Similarly, in the laboratory incubation experiment, we observed a close relationship among soil respiration, Ca2+ content, and SOC pools by the 1st principal component, which explained 63% of the experiment variation. The separation between limed and control plots were even more highlighted than in the field experiment, and the same tendency of gypsum rates was observed in the 1st discriminant axis (i.e. 0G N 3G N 6G N 9G). Table 2 Lime effects on soil fertility attributes in the field experiment, one year after lime and gypsum reapplications and in the laboratory experiment, after 16 months of incubation. Depth, cm
Lime
Fielda Al3+
Laboratory Ca2+
Mg2+
K+
pH
mmolc dm−3 0–5 5–10 10–20 20–40 40–60
Control SL Control SL Control SL Control SL Control SL
1.9 ns 0.03 2.6 ns 0.7 1.3 ns −0.2 1.0 A −3.1 B 1.2 A −0.12 B
13.0 B 27.5 A 7.1 B 22.2 A 11.9 B 19.4 A 14.3 B 22.2 A 10.5 B 19.1 A
Ca2+ mmolc dm−3
−15.2 A −28.2 B −17.0 B −10.6 A 0.0 ns −2.2 0.9 A −1.7 B 2.7 A 1.9 B
39.0 38.5 31.0 25.8 20.2 17.6 16.3 17.4 10.3 12.2
ns ns ns ns ns ns ns ns ns ns
−0.2 B 0.3 A −0.4 B 0.2 A −0.2 ns 0.0 ns 0.0 ns 0.2 ns 0.0 ns 0.2 ns
2.5 4.0 – – – – – – – –
Different uppercase letters indicate significant difference between lime treatments within each soil depth by the LSD test at p b 0.01. ns: not significant. – not applicable. a Results of the field experiment represent the difference between the values found before and one year after the lime and gypsum reapplications.
In the field experiment, β-glycosidase activity was significantly increased on topsoil by lime and gypsum treatments, especially in the 0–5 cm layer, in which lime application provided increases of 10.12 g kg−1 h−1 of the enzyme activity (Table 3). On the 10–20 cm layer, we did not observe significant effects. The stocks of HWEOC and POXC were also significantly increased on the topsoil by the Ca-based amendments (Table 3). These increments have driven a significant increase of 0.26 and 0.28 Mg ha−1 of the 0–60 cm accumulated stocks of HWEOC and POXC, respectively. In the laboratory incubation experiment, we observed increases in soil respiration in response to lime and gypsum treatments (Tables 1 and 3). The respiration rates were higher in the first 30 months, and they tended to reduce and become more constant after this initial period (data not shown). The stocks of HWEOC and POXC were also significantly increased in 0.15 and 0.25 Mg ha−1, respectively, due to lime and gypsum applications in the laboratory incubation (Table 3). We have observed linear increases in the short-term gains of HWEOC and POXC stocks in response to gypsum applications with and without lime in the field experiments. Likewise, the same linear increases were observed in the laboratory experiment (Fig. 4). The stocks of HWEOC and POXC were significantly increased by the soil biological attributes and the Ca+2 content in the field and laboratory experiments (Fig. 5). The increment of each mg kg−1 of β-glycosidase activity in the field experiment, contributed with the increase of 0.02 and 0.03 Mg ha−1 of HWEOC and POXC stocks in the 0–20 cm layer, respectively. Likewise, in the laboratory incubation, the increase of each g kg− 1 of soil respiration, promoted the increment of 0.63 and 0.39 Mg ha− 1 of HWEOC and POXC stocks on the evaluated layer of 0–5 cm. For the Ca2 + in the field experiment, the increase of each mmolc dm− 3 resulted in an increment of 0.03 Mg ha−1 of HWEOC and POXC stocks. For the incubation experiment, the gains provided by Ca2+ were 0,002 and 0,004 Mg ha−1 for HWEOC and POXC stocks, respectively (Fig. 5). 4. Discussion 4.1. Effects of lime and gypsum on soil fertility and soybean yield The significant improvements on soil fertility quality one year after the lime and gypsum reapplications demonstrate the efficiency of
528
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
Fig. 3. Discriminant analysis of principal components (DACP) for the different lime and gypsum rates (G, Mg ha−1) treatments in the a) field; and b) laboratory; experiments.
both Ca-based soil amendments mainly to increase the Ca2+ and reduce the Al3+ contents. Since the Al3+ values found before the reapplications were low at the topsoil layer of 0–20 cm (i.e. 1.9 and 0.2 mmolc dm−3 for control and SL, respectively), it justifies the lack of significance of lime and gypsum applications on soil surface. However, at the 20–40 and 40–60 cm layers, in which the Al3+ contents were higher (6.0 and 4.2 mmolc dm−3 for control and SL, respectively) lime and gypsum provided significant reductions in their contents. These results agree with Caires et al. (2016), who observed significant increments of Ca2+ contents all along the soil profile and reductions in Al3 + saturation in deeper layers as short term effects of gypsum applications (i.e. one year) combined with nitrogen fertilization. According to the authors, the amelioration of soil fertility in deeper layers can promote better maize root development, and consequently a higher nitrogen use efficiency. Positive effects of lime and gypsum on crop productivity are found overwhelmingly on maize crop or grasses (i.e. Poaceae family) in general (Crusciol et al., 2014; Michalovicz et al., 2014; Pauletti et al., 2014; Zandoná et al., 2015; Caires et al., 2016) while studies showing
significant increases in soybean productivity are more rarely found (Joris et al., 2016). Several reasons are pointed out to explain why cereals and soybeans present different responses to lime and gypsum applications. Root cation exchange capacity (RCEC) is lower for cereal crops such as maize and wheat (i.e. 10–20 cmolc kg−1) when compared with soybean (40–80 cmolc kg−1) (Fernandes and Souza, 2006). The RCEC can affect the plant efficiency in absorbing nutrients by raising the concentration of cations at the root and influencing the relative proportions of ions of different valency at the root (Asher and Ozanne, 1961). In addition, soybean presents a higher sulfur translocation efficiency (Silva et al., 2003) and a capacity of penetrating in acid subsoils (Caires et al., 2008). In this way, cereals tend to respond better to soil changes provided by Ca-based soil amendments applications mainly because they are less efficient than soybean in Ca uptake and sulfur translocation. The leaching and losses of magnesium and potassium due to gypsum applications are also reported by several authors (Michalovicz et al., 2014; Pauletti et al., 2014; Zandoná et al., 2015; Basso et al., 2016). For this reason, lime application has been recommended to be applied
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
529
Table 3 Lime effects in the stocks of SOC pools, accumulated soil respiration and β-glycosidase activity in the field experiment, one year after lime and gypsum reapplications and in the laboratory experiment, after 16 months of incubation. Depth, cm
Lime
Fielda
Laboratory
HWEOC Mg ha 0–5 5–10 10–20 20–40 40–60 0–60
Control SL Control SL Control SL Control SL Control SL Control SL
POXC
−1
0.14 B 0.25 A 0.18 B 0.25 A 0.07 B 0.15 A −0.02 ns −0.03 −0.03 ns −0.03 0.34 B 0.60 A
β-glycosidase g kg
0.21 B 0.27 A 0.08 B 0.21 A 0.25 B 0.31 A 0.11 ns 0.10 0.06 ns 0.11 0.72 B 1.00 A
−1
11.87 B 21.99 A 5.55 B 12.07 A 1.59 ns 3.00 – – – – – –
h
−1
HWEOC Mg ha 1.00 B 1.15 A – – – – – – – – – –
POXC
−1
Respiration g kg−1 day−1
2.73 B 2.98 A – – – – – – – – – –
4.64 B 4.84 A – – – – – – – – – –
Different uppercase letters indicate significant difference between lime treatments within each soil depth by the LSD test at p b 0.01. ns: not significant. HWEOC: hot water extractable organic carbon; POXC: permanganate oxidizable organic carbon; SOC: total organic carbon; RESP: Soil Basal Respiration. a Results of the field experiment represent the difference (Δ) between the values found before and one year after the lime and gypsum reapplications.
together with gypsum to compensate the losses. However, in our study, the Mg contents were higher in control plots all along the soil profile, with higher differences in the soil surface, indicating that the ions may have been translocated to deeper depths. On the other hand, the K+ content was not influenced by lime and gypsum treatments, and we observed slight increases all along the soil profile. Therefore, although the lime and gypsum reapplications resulted in immediate beneficial effects for the soil fertility, it did not reflect in the soybean crop productivity in the short-term experiment. However, significant improvements in the grain and Biomass-C production can be expected throughout the years in response to the soil quality increase, as already demonstrated by the long-term study in this same experimental area (Inagaki et al., 2016). 4.2. Short-term effects of lime on SOC pools on crop fields The results of our study support the use of lime and gypsum as strategies to increase SOC stocks in crop fields. The effects of lime on SOC stocks have been widely discussed in the literature, with studies indicating either losses as gains in function of the technique use (Paradelo et al., 2015). In a recent study developed by Aye et al. (2016) in a sodosol (29% of clay) at Victoria - Australia, the authors found depletion of SOC due to lime applications in a 34-year trial with low Biomass-C input and no effect on a 5-year unimproved pasture. Higher biological activity was pointed out as the main factor for SOC decrease. According to the authors, the Biomass-C input was not sufficient to compensate the losses caused by the increment of microbial activity. On the other hand, in our long-term field study, even with the relatively low Biomass-C input rate, ranging from 2.8 to 3.2 Mg ha−1 year−1, we were able to observe significant increments of SOC pools stocks (very sensitive variables to soil degradation) in response to lime and gypsum applications in this same experimental area (Inagaki et al., 2016). Likewise, significant increase of labile SOC pools and biological activity were observed after short-term evaluation from lime and gypsum reapplications. Since soybean crop yield was not significantly influenced by the treatments, the Biomass-C input may has caused a lower influence over such short-term increases in labile SOC, when compared with the long-term effects. The main factor related to the preservation of SOC stocks either in the field or in the laboratory experiment was the soil biological activity, measured by β-glycosidase activity and soil respiration, respectively. This positive influence of biological variables in the increase of SOC stocks demonstrates that the improvement of soil microbial activity
was not deleterious to the soil health. In addition, calcium ions have been shown an important role in the SOC protection (Briedis et al., 2012b; Inagaki et al., 2016), fact that was also observed in our study, and therefore, it can be a reasonable explanation for the short-term increases. In our long-term field experiment (Inagaki et al., 2016), the net rates of total SOC sequestration provided by surface-lime + gypsum treatments varied from 3.9 to 5.3 Mg ha− 1 year−1 during 15 years from the experiment establishment. In addition, the stocks of labile SOC pools (i.e. HWEOC and POXC) in limed soils were significantly higher than in the control plots. For this short-term evaluation one year after the lime and gypsum reapplications, although we did not observe significant improvements in the total SOC stock, the same was not depleted, as stated in many studies evaluating SOC stocks in response to liming few months or years after the applications. On the other hand, the differences in the labile SOC pools and enzyme activity between limed and non-limed plots were evident even only a year after the reapplications. The HWEOC is a representative of the microbial biomass, since it contains a high presence of microbial derived SOC (Haynes and Francis, 1993). In the same way, POXC stands out as an efficient method to measure labile SOC, once it is highly correlated with microbial biomass and particulate SOC (Culman et al., 2012). Both labile SOC forms together with enzyme activities have been largely used as parameters to evaluate soil quality due to their sensitivity to land use and management changes (Makoi and Ndakidemi, 2008; Uchida et al., 2012; Hurisso et al., 2016). The expressive response of these variables to short-term lime and gypsum application, in this fact emphasizes their capacity to work as soil quality indicators. 4.3. The use of undisturbed soil samples for incubation experiments The positive influences of lime and gypsum applications on the increase of labile SOC pools (i.e. HWEOC and POXC) and the lack of depletion of the total SOC stock in the laboratory incubation experiment support the use of Ca-based soil amendments to provide carbon sequestration and environmental sustainability. The results observed in the incubation experiment confirm the observations detected in our field trial and they go in the opposite direction of the results of Fuentes et al. (2006). Evaluating soil basal respiration in function of liming, the authors found initially higher rates for limed samples. However, a shift occurred after 56 days of incubation, when control samples started presenting higher respiration rates. In this case, since no plant residue was available for the microbes, they immediately started depleting the
530
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
Fig. 4. Increase of hot water extractable organic carbon (HWEOC) and permanganate oxidizable organic carbon (POXC) stocks by gypsum rates with and without liming in the a) field experiment at 0–60 cm layer one year after the lime and gypsum reapplications; and in the b) laboratory experiment after 16 months of incubation. Gains of field experiment represent the difference between the values found before and one year after the lime and gypsum reapplications.
SOC, stimulated by the lime addition. When the substrate availability became scarce in the soil, the microbial activity became lower, the moment that the shift occurred. Therefore, the increase of SOC pools because of the higher microbial activity (i.e. soil respiration) in our experiment may be explained by the addition of crop residues over the soil surface, which has worked as substrate for the microbiota during the experimental period. Such results agree with Wong et al. (2009), who demonstrated higher microbial activity in treatments with gypsum + plant residues addition in an incubation experiment. In our study, such SOC accumulation was favored by the maintenance of soil structure in the undisturbed sample, which allowed the carbon sequestration along time. Although no significant increments of the total SOC were found, longer experimental periods might demonstrate higher differences, as the SOC turnover increases the stocks in the soil due to the biomass-C input (Briedis et al., 2012a). The results obtained from the laboratory incubation are supported by the field experiment, in which we also found increments in labile SOC pools in response to the higher microbial activity (i.e. β-glycosidase activity).
The majority of the studies demonstrating depletion of SOC stocks as a result of liming make use of soil disturbance operations (Caires et al., 2006; Fuentes et al., 2006; Yagi et al., 2014; Aye et al., 2016; Joris et al., 2016). Such soil disturbance provided by lime incorporation causes the breakdown of soil macroaggregates, exposing the previously protected SOC in their inner to decomposition process by the microbial activity (Tivet et al., 2013). Deleterious effects in response of Ca-based soil amendments found under conventional tillage system conditions also corroborates to explain the impact of soil disturbance. West and McBride (2005) highlighted significant amounts of CO2 emitted from lime applications in USA, where a significant part of the agricultural areas are managed under conventional tillage. In the conversion of a pastureland to crop field, Caires et al. (2006) demonstrated decreases of SOC content of a Brazilian Oxisol in response to lime incorporation by soil plowing and harrowing. Likewise, also in a pastureland – crop field conversion, Joris et al. (2016) observed faster neutralization reactions and decreases in SOC due to lime incorporation. In our long-term lime and gypsum field experiment, we demonstrated that lime incorporation can be deleterious to SOC stocks, and because
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
531
Fig. 5. Influence of soil biological attributes (gains in β-glycosidase activity and soil respiration) and Ca+2 content on labile SOC pools (Hot water extractable organic C – HWEOC; and Permanganate oxidizable organic C – POXC) in the a) field experiment one year after the lime and gypsum reapplications; and in the b) laboratory experiment after 16 months of incubation.
of this, the surface-lime application provides in the best alternative for the conversion of pastureland to crop fields (Inagaki et al., 2016). Thus, for laboratory incubation experiments, it is important to evaluate the lime and gypsum influence using undisturbed soil samples. Their use with application of crop residues on soil surface, therefore, is an efficient tool to simulate the effects of lime and gypsum application on conservation agriculture in highly weathered soil. 4.4. Responses of labile SOC pools to gypsum rates in the field and incubation experiment For the gypsum treatments, the linear increases of labile SOC pools were similar to the ones observed in our long-term experiment (Inagaki et al., 2016). However, for the field experiment, the angular coefficients were higher than in the laboratory incubation, demonstrating a higher potential of gypsum to increase SOC in field trials than in soil incubation experiments. Wong et al. (2009), also detected increases in the soil biological quality in function of gypsum + plant residues addition in an incubation experiment. The authors emphasized that the amelioration of
the soil chemical quality may create a more favorable environment for the microbial development. This factor can be one of the main mechanisms to explain gypsum effects either in the field (Inagaki et al., 2016) or in a soil incubation trial (Wong et al., 2009). The gypsum addition in the crop field experiment was a reapplication in the already improved plots by lime and gypsum applications in 1998. This fact may had contributed for the higher field responses when compared to the laboratory incubation experiment, once soils with higher fertility levels present a higher SOC accumulation efficiency (Briedis et al., 2016). Another factor that could possibly influence the gypsum effects in the field experiment is the presence of plants and their root system in the soil profile. According to Caires et al. (2016), the gypsum application can favor the plants root growth, mainly in response to Ca2 + increment along the soil profile. Since the plant roots are recognized as a source of SOC (Johnson et al., 2006), and they can act as an important soil aggregation agent (Rillig et al., 2015), modifications of the SOC stocks in response to gypsum addition may be likely related to changes in their properties or distribution along the soil profile. Therefore, more studies relating the modifications in the root system and its properties in response to
532
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
gypsum application can contribute to understand more its effect on SOC sequestration. 5. Conclusions We conclude that lime and gypsum applications can highly increase soil microbial activity and stocks of labile SOC pools in long-term no-till system. We demonstrated that although the soil microbial activity is highly increased after 1 and 1.5 years from the applications (field and laboratory experiments, respectively), it does not lead to SOC depletion on conservation agriculture. The increase of soil biological activity and Ca2 + contents were the main factors governing the increase of SOC stocks. The laboratory incubation experiment confirmed the results obtained in the field, and it has demonstrated to be an efficient way to simulate no-till conditions. Our finds open opportunities for the development of new projects to simulate no-till conditions under controlled conditions. Funding This work was supported by CNPq (Grant 482292/2012-1) and CAPES (Grant 99999.006792/2014-06) for research funding and the scholarship for corresponding author and CNPq grant 304945/2013-7 for a scholarship to the third author. Acknowledgments We would like to thank CAPES for providing the first author with a scholarship and the Laboratório de Matéria Orgânica do Solo (LABMOS) of the State University of Ponta Grossa for providing the structure to develop the soil analyses for this study. References Araújo, L.G., 2016. Uso do gesso e sua influência na produção de cana-de-açúcar, atributos químicos e estoque de carbono no solo de cerrado. Faculdade de Agronomia e Medicina Veterinária. Universidade de Brasília, p. 101. Asher, C.J., Ozanne, P.G., 1961. The cation exchange capacity of plant roots, and its relationship to the uptake of insoluble nutrients. Aust. J. Agric. Res. 12 (5), 755–766. Aye, N.S., Sale, P.W., Tang, C., 2016. The impact of long-term liming on soil organic carbon and aggregate stability in low-input acid soils. Biol. Fertil. Soils 1–13. Basso, C.J., Somavilla, L., da Silva, R.F., Santi, A.L., 2016. Intervenção mecânica e gesso agrícola para mitigar o gradiente vertical de cátions sob sistema de plantio direto. Pesquisa Agropecuária Tropical (Agricultural Research in the Tropics) 45, 456–463. Briedis, C., Sá, J.C.d.M., Caires, E.F., de Fátima Navarro, J., Inagaki, T.M., Boer, A., de Oliveira Ferreira, A., Neto, C.Q., Canalli, L.B., Bürkner dos Santos, J., 2012a. Changes in organic matter pools and increases in carbon sequestration in response to surface liming in an Oxisol under long-term no-till. Soil Sci. Soc. Am. J. 76, 151–160. Briedis, C., Sá, J.C.d.M., Caires, E.F., Navarro, J.d.F., Inagaki, T.M., Boer, A., Neto, C.Q., Ferreira, A.d.O., Canalli, L.B., Santos, J.B.d., 2012b. Soil organic matter pools and carbonprotection mechanisms in aggregate classes influenced by surface liming in a no-till system. Geoderma 170, 80–88. Briedis, C., Sá, J.C.d.M., Lal, R., Tivet, F., de Oliveira Ferreira, A., Franchini, J.C., Schimiguel, R., da Cruz Hartman, D., dos Santos, J.Z., 2016. Can highly weathered soils under conservation agriculture be C saturated? Catena 147, 638–649. Caires, E., Barth, G., Garbuio, F., 2006. Lime application in the establishment of a no-till system for grain crop production in Southern Brazil. Soil Tillage Res. 89, 3–12. Caires, E., Pereira Filho, P., Zardo Filho, R., Feldhaus, I., 2008. Soil acidity and aluminium toxicity as affected by surface liming and cover oat residues under a no-till system. Soil Use Manag. 24, 302–309. Caires, E., Haliski, A., Bini, A., Scharr, D., 2015. Surface liming and nitrogen fertilization for crop grain production under no-till management in Brazil. Eur. J. Agron. 66, 41–53. Caires, E.F., Zardo Filho, R., Barth, G., Joris, H.A., 2016. Optimizing nitrogen use efficiency for no-till corn production by improving root growth and capturing NO 3-N in subsoil. Pedosphere 26, 474–485. Chan, K., Heenan, D., 1999. Lime-induced loss of soil organic carbon and effect on aggregate stability. Soil Sci. Soc. Am. J. 63, 1841–1844. Crusciol, C.A.C., Foltran, R., Rossato, O.B., McCray, J.M., Rossetto, R., 2014. Effects of surface application of calcium-magnesium silicate and gypsum on soil fertility and sugarcane yield. Rev. Bras. Ciênc. Solo 38, 1843–1854. Culman, S.W., Snapp, S.S., Freeman, M.A., Schipanski, M.E., Beniston, J., Lal, R., Drinkwater, L.E., Franzluebbers, A.J., Glover, J.D., Grandy, A.S., 2012. Permanganate oxidizable carbon reflects a processed soil fraction that is sensitive to management. Soil Sci. Soc. Am. J. 76, 494–504.
Curtin, D., Beare, M.H., Hernandez-Ramirez, G., 2012. Temperature and moisture effects on microbial biomass and soil organic matter mineralization. Soil Sci. Soc. Am. J. 76, 2055–2067. Embrapa, 2013. Sistema Brasileiro de Classificação de Solos - SiBCS (3ª edição). Centro Nacional de Pesquisa de Solos, Rio de Janeiro. Fernandes, M., Souza, S., 2006. Absorção de nutrientes. Nutrição mineral de plantas. Sociedade Brasileira de Ciência do Solo, Viçosa, pp. 115–152. Ferreira, D., 2008. Programa Sisvar, versão 5.1: programa de análises estatísticas. DEX/ UFLA, Lavras. Fuentes, J.P., Bezdicek, D.F., Flury, M., Albrecht, S., Smith, J.L., 2006. Microbial activity affected by lime in a long-term no-till soil. Soil Tillage Res. 88, 123–131. Ghani, A., Dexter, M., Perrott, K., 2003. Hot-water extractable carbon in soils: a sensitive measurement for determining impacts of fertilisation, grazing and cultivation. Soil Biol. Biochem. 35, 1231–1243. Haynes, R., Francis, G., 1993. Changes in microbial biomass C, soil carbohydrate composition and aggregate stability induced by growth of selected crop and forage species under field conditions. J. Soil Sci. 44, 665–675. Hurisso, T.T., Culman, S.W., Horwath, W.R., Wade, J., Cass, D., Beniston, J.W., Bowles, T.M., Grandy, A.S., Franzluebbers, A.J., Schipanski, M.E., 2016. Comparison of permanganate-oxidizable carbon and mineralizable carbon for assessment of organic matter stabilization and mineralization. Soil Sci. Soc. Am. J. 80, 1352–1364. Inagaki, T.M., Sá, J.C.d.M., Caires, E.F., Gonçalves, D.R.P., 2016. Lime and gypsum application increases biological activity, carbon pools, and agronomic productivity in highly weathered soil. Agric. Ecosyst. Environ. 231, 156–165. Jenkinson, D., Powlson, D.S., 1976. The effects of biocidal treatments on metabolism in soil—V: a method for measuring soil biomass. Soil Biol. Biochem. 8, 209–213. Johnson, J.-F., Allmaras, R., Reicosky, D., 2006. Estimating source carbon from crop residues, roots and rhizodeposits using the national grain-yield database. Agron. J. 98, 622–636. Joris, H.A.W., Caires, E.F., Scharr, D.A., Bini, Â.R., Haliski, A., 2016. Liming in the conversion from degraded pastureland to a no-till cropping system in Southern Brazil. Soil Tillage Res. 162, 68–77. Makoi, J.H., Ndakidemi, P.A., 2008. Selected soil enzymes: examples of their potential roles in the ecosystem. Afr. J. Biotechnol. 7. Michalovicz, L., Müller, M.M.L., Foloni, J.S.S., Kawakami, J., Nascimento, R.d., Kramer, L.F.M., 2014. Soil fertility, nutrition and yield of maize and barley with gypsum application on soil surface in no-till. Rev. Bras. Ciênc. Solo 38, 1496–1505. Nelson, D.W., Sommers, L.E., 1996. Total carbon, organic carbon and organic matter. Method of soil analysis: chemical methods. Soil Sci. Soc. Am. J. 961–1010. Paradelo, R., Virto, I., Chenu, C., 2015. Net effect of liming on soil organic carbon stocks: a review. Agric. Ecosyst. Environ. 202, 98–107. Pauletti, V., Pierri, L.d., Ranzan, T., Barth, G., Motta, A.C.V., 2014. Efeitos em longo prazo da aplicação de gesso e calcário no sistema de plantio direto. Rev. Bras. Ciênc. Solo 38, 495–505. Pavan, M.A., Bloch, M.d.F., Zempulski, H.d.C., 1992. Manual de análise química de solo e controle de qualidade. IAPAR. Peel, M.C., Finlayson, B.L., McMahon, T.A., 2007. Updated world map of the Köppen-Geiger climate classification. Hydrol. Earth Syst. Sci. Discuss. 4, 439–473. R Development Core Team, 2014. R: a language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing; 2012. Open access available at. http://cran.r-project.org. Rillig, M.C., Aguilar-Trigueros, C.A., Bergmann, J., Verbruggen, E., Veresoglou, S.D., Lehmann, A., 2015. Plant root and mycorrhizal fungal traits for understanding soil aggregation. New Phytol. 205, 1385–1388. Sá, J.C.d.M, Bürkner dos Santos, J., Lal, R., De Moraes, A., Tivet, F., Sá, M.F.M., Briedis, C., de Oliveira Ferreira, A., Eurich, G., 2013. Soil-specific inventories of landscape carbon and nitrogen stocks under no-till and native vegetation to estimate carbon offset in a subtropical ecosystem. Soil Sci. Soc. Am. J. 77, 2094–2110. Silva, D.J., Venegas, V.H.A., Ruiz, H.A., Sant'Anna, R., 2003. Translocação e redistribuição de enxofre em plantas de milho e de soja. Pesq. Agropec. Bras., Brasília 38, 715–721. Survey Staf, Soil, 2010. Keys to Soil Taxonomy. 11th ed. United States Department of Agriculture -Natural Resources Conservation Service, Washington, DC. Tirol-Padre, A., Ladha, J.K., 2004. Assessing the reliability of permanganate-oxidizable carbon as an index of soil labile carbon. Soil Sci. Soc. Am. J. 68, 969–978. Tivet, F., Sá, J.C.d.M., Lal, R., Briedis, C., Borszowskei, P.R., dos Santos, J.B., Farias, A., Eurich, G., da Cruz Hartman, D., Junior, M.N., 2013. Aggregate C depletion by plowing and its restoration by diverse biomass-C inputs under no-till in sub-tropical and tropical regions of Brazil. Soil Tillage Res. 126, 203–218. Uchida, Y., Nishimura, S., Akiyama, H., 2012. The relationship of water-soluble carbon and hot-water-soluble carbon with soil respiration in agricultural fields. Agric. Ecosyst. Environ. 156, 116–122. West, T.O., McBride, A.C., 2005. The contribution of agricultural lime to carbon dioxide emissions in the United States: dissolution, transport, and net emissions. Agric. Ecosyst. Environ. 108, 145–154. Wong, V.N., Dalal, R.C., Greene, R.S., 2009. Carbon dynamics of sodic and saline soils following gypsum and organic material additions: a laboratory incubation. Appl. Soil Ecol. 41, 29–40. Wyngaard, N., Echeverría, H.E., Rozas, H.R.S., Divito, G.A., 2012. Fertilization and tillage effects on soil properties and maize yield in a Southern Pampas Argiudoll. Soil Tillage Res. 119, 22–30. Yagi, R., Fidalski, J., Tormena, C.A., 2014. A incorporação de calcário em sistema plantio direto consolidado reduz o estoque de carbono em macroagregados do solo. Ciênc. Rural 44, 1962–1965. Zandoná, R.R., Beutler, A.N., Burg, G.M., Barreto, C.F., Schmidt, M.R., 2015. Gesso e calcário aumentam a produtividade e amenizam o efeito do déficit hídrico em milho e soja. Pesquisa Agropecuária Tropical (Agricultural Research in the Tropics) 45.
Contents lists available at ScienceDirect
Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv
Why does carbon increase in highly weathered soil under no-till upon lime and gypsum use? Thiago Massao Inagaki a, João Carlos de Moraes Sá b,⁎, Eduardo Fávero Caires b, Daniel Ruiz Potma Gonçalves b a b
Technical University of Munich, Chair of Soil Science, Institute for Advanced Study, Email-Ramann Str. 2, 85354 Freising, Bayern, Germany Department of Soil Science and Agricultural Engineering, State University of Ponta Grossa, Av. Carlos Cavalcanti 4748, Campus de Uvaranas, 84030-900, Ponta Grossa, Paraná, Brazil
H I G H L I G H T S
G R A P H I C A L
A B S T R A C T
• Lime and gypsum use in field and incubation experiments increases soil C. • Increase of calcium content and soil biological activity resulted in SOC gains. • Calcium and labile SOC formed complex with mineral soil fractions. • Associations between calcium and labile SOC can be the pathway to increase C sequestration.
a r t i c l e
i n f o
Article history: Received 26 January 2017 Received in revised form 24 April 2017 Accepted 29 April 2017 Available online xxxx Editor: Ajit Sarmah Keywords: Carbon sequestration Soil biology Acid soils Soil organic matter Soil correction Incubation
a b s t r a c t Field experiments have been used to explain how soil organic carbon (SOC) dynamics is affected by lime and gypsum applications, however, how SOC storage occurs is still debatable. We hypothesized that although many studies conclude that Ca-based soil amendments such as lime and gypsum may lead to SOC depletion due to the enhancement of microbial activity, the same does not occur under conservation agriculture conditions. Thus, the objective of this study was to elucidate the effects of lime and gypsum applications on soil microbial activity and SOC stocks in a no-till field and in a laboratory incubation study simulating no-till conditions. The field experiment was established in 1998 in a clayey Oxisol in southern Brazil following a completely randomized blocks design with a split-plot arrangement and three replications. Lime and gypsum were surface applied in 1998 and reapplied in 2013. Undisturbed soil samples were collected before the treatments reapplications, and one year after. The incubation experiment was carried out during 16 months using these samples adding crop residues on the soil surface to simulate no-till field conditions. Lime and gypsum applications significantly increased the labile SOC stocks, microbial activity and soil fertility attributes in both field and laboratory experiments. Although the microbial activity was increased, no depletion of SOC stocks was observed in both experiments. Positive correlations were observed between microbial activity increase and SOC gains. Labile SOC and Ca2+ content increase leads to forming complex with mineral soil fractions. Gypsum applications performed a higher influence on labile SOC pools in the field than in the laboratory experiment, which may be related to the presence of active root system in the soil profile. We conclude that incubation experiments using lime and gypsum in undisturbed samples confirm that soil microbial activity increase does not deplete SOC stocks under conservation agriculture. © 2017 Elsevier B.V. All rights reserved.
Abbreviations: SOC, Soil organic carbon; SL, Surface applied lime; HWEOC, Hot-water extractable organic C; POXC, Permanganate oxidizable organic carbon; TOC, Total organic carbon. ⁎ Corresponding author. E-mail address: [email protected] (J.C. de Moraes Sá).
http://dx.doi.org/10.1016/j.scitotenv.2017.04.234 0048-9697/© 2017 Elsevier B.V. All rights reserved.
524
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
1. Introduction The use of lime on agriculture has been reported as an effective practice to control soil acidity and minimize the toxicity of Al3+, mainly in tropical and subtropical environments. Gypsum has also been recognized by its efficiency to reduce the Al3+ toxicity in deeper layers and contents (Caires et al., 2015). Although the to increase Ca2+ and SO2− 4 influence of both practices, especially lime, on soil organic carbon (SOC) dynamics has been intensively discussed, the factors and processes which govern their increases or decreases are not fully understood (Paradelo et al., 2015). Reports indicating increase (Briedis et al., 2012a, 2012b), decreases (Chan and Heenan, 1999; Fuentes et al., 2006; Aye et al., 2016) and no effect (Wyngaard et al., 2012) of lime applications on SOC stocks demonstrate the influence of several drivers such as climate, soil texture, soil management and biomass input. Gypsum effects on SOC although less studied than lime have demonstrated a significant effect to promote carbon sequestration, as demonstrated by Araújo (2016) in sugarcane fields and Inagaki et al. (2016) in long-term no-till field. Higher biomass inputs from crop residues in soils resulting from the lime and gypsum applications have been pointed out as the main source of SOC increases in soils (Briedis et al., 2012a; Inagaki et al., 2016). In addition, the presence of Ca2 + ions are recognized to work as an ionic bridge between soil organic matter and clay particles, increasing soil aggregation and providing C protection (Briedis et al., 2012b). The increase of biomass input and the aggregating mechanisms of Ca2 + in soils work to increase carbon sequestration in long-term experiments when associated with conservation agriculture. In contrast, soil disturbance and low biomass input stand out as the main reasons for SOC depletions in liming experiments (Caires et al., 2006; Yagi et al., 2014; Aye et al., 2016). In a recent study, Aye et al. (2016) reported reduction of SOC stocks in long-term liming experiments, citing the fields low Cbiomass inputs as the main reason for this depletion. According to the authors, the crop residue input was not enough to compensate the higher SOC mineralization caused by lime addition. Incubation experiments in soils have been widely used, mainly because of their capacity to create ideal experimental conditions, eliminating interference of humidity and temperature on soil microbial activity (Curtin et al., 2012). However, incubation experiments performed to assess the lime and gypsum influence on SOC usually make use of disturbed samples with no crop residue addition (Fuentes et al., 2006; Wong et al., 2009), which commonly results in SOC depletion as a consequence of the microbial biomass activity increase. Therefore, the use of new methods to evaluate the lime and gypsum activity in laboratory studies is necessary to better understand its influence on SOC dynamics in conservation agriculture conditions. We hypothesized that although many studies conclude that Cabased soil amendments such as lime and gypsum may lead to SOC depletion due to the enhancement of microbial activity, the same does not occur under conservation agriculture conditions. Thus, the objective of this study was to evaluate the effects of lime and gypsum applications on SOC pools, microbial activity and soil fertility in a notill field and in a pilot incubation experiment using undisturbed soil with crop residue additions to simulate conservation agriculture conditions. 2. Material and methods 2.1. Site description and soil The experiment was performed in a no-till crop field area in Ponta Grossa PR, southern Brazil (25°10′S, 50°05′W). The annual precipitation is approximately 1550 mm with average maximum and minimum temperatures of 22 and 13 °C, respectively. According to Köppen–Geiger System (Peel et al., 2007), the climate is described as Cfb type (mesothermal, humid, subtropical), with mild summer and frequent
frosts during the winter. The average altitude is 970 m above sea level. The soil is classified as red Latosol (Brazilian classification, Embrapa (2013)) equivalent to a clayey, kaolinitic, thermic Rhodic Hapludox (Soil Survey Staff, 2010), with 610 g kg−1 of clay. 2.2. Soil sampling and field experimental design The experimental area was previously used as a pastureland with no historical of lime and gypsum applications. In 1998, the lime and gypsum experiment was established in a completely randomized design with three replicates. The plots sizes were 224 m2 (32 × 7 m) and the subplots sizes were 56 m2 (8 × 7 m). In the main plots, the treatments were assigned as follow: 1) control, no lime application; and 2) Surface lime application (SL) of 4.5 Mg ha− 1, divided in three yearly applications of 1.5 Mg ha− 1 from the establishment of the experiment (Fig. 1). The lime rate was calculated to raise the base saturation in the topsoil (0–20 cm) to 70%. In the subplots, four rates of gypsum were surface-applied: 0, 3, 6, and 9 Mg ha− 1. Further information about the experimental site was described by Inagaki et al. (2016). In 2013, the lime treatment was reapplied in a full surface application of 4 Mg ha−1. Gypsum treatments were also reapplied on soil surface at the same rates of 0, 3, 6 and 9 Mg ha−1. Soil samples were collected in August 2013 at the depths of 0–0.05, 0.05–0.10, 0.10–0.20, 0.20–0.40 and 0.40–0.60 m before the lime and gypsum reapplications, and in August 2014, one year after. During the crop season, the soil was cultivated with soybean crop (Glycine max) during the summer and let under fallow during the winter. All the soil analyses were performed in both years to calculate the short-term gains. 4.5, 20 and 37 kg ha−1 of NPK at sowing in band application were used in the area for soybean crop. 2.3. Pilot incubation experiment For this experiment, we have developed a pilot incubation trial using undisturbed soil samples with addition of crop residues on soil surface, in order to mimic the conditions of a no-till field. No study, in our knowledge, has examined the lime and gypsum effects under these conditions. We collected 24 undisturbed samples (5 × 5 cm steel rings) randomly from a control plot (i.e. no lime and no gypsum application) in the 0–0.05 m layer in 2013. The experimental design used was completely randomized with factorial 2 × 4, with three replicates. The factors evaluated in the experiment were: a) two liming treatments: Control (no lime) and surface lime application of a rate equivalent to 4 Mg ha−1; and b) Gypsum applied in the rates equivalent to 0, 3, 6 and 9 Mg ha−1 (Fig. 2). The rates were the same applied on the field experiment. Both lime and gypsum treatments were manually applied over the top of each undisturbed sample. Before the samples incubation, we added an equivalent of 10 Mg ha−1 of maize residues (Zea mays – 448 g kg− 1 of C content) on the surface of each sample in order to simulate the C-biomass input in no-till system. Twelve months after, we added the equivalent of 4 Mg ha−1 of soybean residue (Glycine max – 389 g kg−1 of C content), simulating a corn-soybean crop rotation. The samples were inside of hermetic closed glass flasks, maintained in a dark chamber under controlled temperature of 28 °C ± 2 °C, and approximately on 50% of the maximum water retention capacity. Samples moisture was maintained constant through water weekly additions. After 480 days of incubation (16 months), the remaining crop residues were manually removed from the surface and the soil was collected, dried under 40 °C and passed by a 2 mm sieve. 2.4. Soil basal respiration The determination of soil basal respiration followed the methodology described by Jenkinson and Powlson (1976). Briefly, each
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
525
Fig. 1. Chronology of the experimental design from 1980 to 2014. Adapted from Inagaki et al. (2016).
undisturbed soil sample was maintained in a 1 L glass flask sealed with a beaker containing 1 M NaOH solution used to capture the CO2 emitted by the sample. Then, a titration with the excess of NaOH was performed with HCl solution 0.5 M and phenolphthalein as an indicator. Flasks incubated only with the NaOH solution were used as blank to correct the results. During the incubation period, basal respiration was measured in two phases: 1st phase - addition maize residues (0–12 months incubation): determinations at 2, 4, 6, 8, 10, 16, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330 and 360 days from the start of incubation. 2nd Phase addition of soybean residues (12 to 16 months): the determinations 362, 364, 366, 368, 370, 372, 376, 390, 420, 450 and 480 days from the start of incubation. In each measurement, the NaOH solutions were replaced in each flask.
2.6. Permanganate oxidizable organic carbon (POXC) The method for SOC extraction by potassium permanganate (KMnO4) was adapted from the studies of Tirol-Padre and Ladha (2004) and Culman et al. (2012). For the SOC extraction, a 0.06 M KMnO4 solution was applied into 1.5 g of soil in a 15 mL centrifuge tube. After the extraction and centrifuging, the supernatant was pipetted into an Erlenmeyer and diluted with deionized water. The extracted SOC was then measured with a spectrometer in 565 nm of absorbance. A standard curve was performed with pre-determined concentrations of KMnO4 solutions and the SOC content of the samples was calculated based in the relationship Absorbance × KMnO4 concentration. 2.7. Total soil organic carbon and nitrogen contents
2.5. Hot water extractable organic C (HWEOC) The determination of the SOC content extracted by hot water was conducted according to the methodology described by Ghani et al. (2003). Briefly, we weighed 1.5 g of soil for each sample in 15 mL centrifuge tubes. The samples were then maintained at 80 °C for 16 h in deionized water. After the extraction with hot water, the samples were centrifuged, the supernatant was pipetted into an Erlenmeyer flask and the content of C was determined by wet combustion, using the Walkley Black method (Nelson and Sommers, 1996), through oxidation by potassium dichromate and titration with ferrous ammonium sulfate.
The contents of total SOC and N was performed by dry combustion with an elementary CN analyzer (TruSpec CN, LECO, St. Joseph, MI, USA). According to de Moraes Sá et al. (2013), the carbonates content of Oxisols and Cambisols of the region are insignificant (b0.25% of the SOC content). For this reason, we considered that the C determined by dry combustion represent the total SOC content of this soil. 2.8. Soil fertility attributes Soil pH was determined in a 0.01 M CaCl2 suspension. The contents of exchangeable Ca, Mg and Al were extracted with a 1 M KCl solution
526
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
Fig. 2. Arrangement of the laboratory incubation experiment following a completely randomized design with three replicates. Four gypsum rates (0, 3, 6 and 9 Mg ha−1) with and without lime application (4 Mg ha−1) were used as treatments. The total incubation period was 16 months. 10 Mg ha−1 of corn and 4 Mg ha−1 of soybean residues were added on the soil surface of all samples at 0 and 12 months of the incubation period to simulate no-till conditions.
and determined by Atomic absorption spectroscopy, and exchangeable K+ by flame photometry according to the procedures described by Pavan et al. (1992).
3. Results
2.9. SOC stocks calculation
One year after the lime and gypsum reapplications in the field experiment, we found significant gains in soil fertility, SOC pools and biological (i.e., enzyme) activity compared with the values found in the previous year (Table 1). Although the soil quality was improved by both treatments, the soybean crop yield was not affected, and no interaction between the two Ca-based soil amendments were found overall. Lime applications significantly decreased the Al3 + contents in deeper layers (20–40 and 40–60 cm), increased the Ca2 + content all along the soil profile, the pH at topsoil, and promoted Mg2+ leaching (Table 2). Similarly, gypsum significantly decreased Al3+ and increased the Ca2+ and Mg2+ content in deeper layers, but it did not change soil pH (Table 1). At the laboratory incubation experiment, significant increases in the Ca2+ content were also observed due to the application of lime and gypsum. Soybean crop productivity ranged from 4.2 Mg ha−1 (i.e. no lime, no gypsum) to 4.7 Mg ha−1 (i.e. SL + 9 G) (data not shown). However, no significant effect of Ca-based soil amendments applications was found.
The calculus for SOC stocks in each layer and in each SOC pool were performed by the following equation:
−1 SOC stock Mg ha −1 SOC content g kg Soil bulk density Mg m−3 depth ðcmÞ ¼ 10
2.10. Statistical analysis The lime and gypsum treatments were analyzed by analysis of variance (ANOVA) using the software SISVAR (Ferreira, 2008). The means of lime treatments were compared using LSD test at p = 0.05. Analysis of simple linear regression were performed using the software R (R Development Core Team, 2014). The criterion for choosing the model was the magnitude of the determination coefficients significant at p b 0.05. A discriminant analysis of principal components was carried out in this study to observe the separation between limed and non-limed plots and the relationship among the soil fertility, crop productivity, biological activity and SOC pools in the field and laboratory experiment. The package ade4 of R software was used in this study (R Development Core Team, 2014).
3.1. Effects of lime and gypsum on soil fertility attributes and crop productivity in field experiment
3.2. Effects of lime and gypsum on SOC pools and biological attributes Increases in the stocks of SOC pools and soil biological attributes due to lime and gypsum applications were observed either in the field as in the laboratory incubation experiments. Control plots presented insignificant changes in the evaluated variables from the year before the lime and gypsum reapplications, and no losses of SOC or biological activity was observed. In the incubation experiment, lime and gypsum treatments significantly increased the stocks of SOC pools, soil respiration
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
527
Table 1 Analysis of variance for field gains and laboratory incubation study. Soil depth cm
0–5
5–10
10–20
20–40
40–60
0–60
Variation Source
Soybean Crop yield
Lime Gypsum Lime × Gypsum Lime Gypsum Lime × Gypsum Lime Gypsum Lime × Gypsum Lime Gypsum Lime × Gypsum Lime Gypsum Lime × Gypsum Lime Gypsum Lime × Gypsum Lime Gypsum Lime × Gypsum
ns ns ns
Field experiment
Laboratory incubation study
HWEOC
POXC
SOC
β-glycosidase
Al
Ca+2
Mg
K
pH
HWEOC
POXC
RESP
SOC
TN
Ca+2
* ** ns ** ** ns ** ** ns ns ns ns ns ns ns * * ns
* * ns * * ns * * ns ns ns ns ns ns ns * * ns
ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns
** * ns ** ** ns ns ns ns ns ns ns ns ns ns – – –
ns ns ns ns ns ns ns ns ns * ns ns * * ns – – –
** L** ns * ns ns * ns ns * L* ns ** L* * – – –
** * ns * ns ns ns ns ns * * ns * ** ** – – –
ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns – – –
* ns ns * ns ns ns ns ns ns ns ns ns ns ns – – –
** L** ns – – – – – – – – – – – – – – –
** L* ns – – – – – – – – – – – – – – –
** L* ns – – – – – – – – – – – – – – –
ns ns ns – – – – – – – – – – – – – – –
ns ns ns – – – – – – – – – – – – – – –
** L** ns
ns = not significant; ** = Significant at p b 0.01; * = Significant at p b 0.05; – = not applicable. HWEOC: hot water extractable organic carbon; POXC: permanganate oxidizable organic carbon; TOC: total organic carbon; TN: Total Nitrogen; RESP: Soil Basal Respiration; L: Linear function.
and Ca2+ content. The total SOC and N stocks stayed in the same level and no interaction was observed between lime and gypsum treatments. At the discriminant analysis of principal components for the field experiment, we can observe a close relationship between soil fertility attributes, SOC pools, β-glycosidase activity and soybean crop productivity in the 1st principal component, which explained 69% of the experiment variation (Fig. 3). Limed and control plots were clearly separated by the first discriminant axis, showing higher levels of SOC accumulation efficiency and lower Al+3 contents. We can also observe a separation between gypsum rates by the 1st discriminant function. The gypsum treatments presented the following sequence of SOC accumulation efficiency: 0G N 3G N 6G N 9G (i.e. G = gypsum rate in Mg ha−1). Similarly, in the laboratory incubation experiment, we observed a close relationship among soil respiration, Ca2+ content, and SOC pools by the 1st principal component, which explained 63% of the experiment variation. The separation between limed and control plots were even more highlighted than in the field experiment, and the same tendency of gypsum rates was observed in the 1st discriminant axis (i.e. 0G N 3G N 6G N 9G). Table 2 Lime effects on soil fertility attributes in the field experiment, one year after lime and gypsum reapplications and in the laboratory experiment, after 16 months of incubation. Depth, cm
Lime
Fielda Al3+
Laboratory Ca2+
Mg2+
K+
pH
mmolc dm−3 0–5 5–10 10–20 20–40 40–60
Control SL Control SL Control SL Control SL Control SL
1.9 ns 0.03 2.6 ns 0.7 1.3 ns −0.2 1.0 A −3.1 B 1.2 A −0.12 B
13.0 B 27.5 A 7.1 B 22.2 A 11.9 B 19.4 A 14.3 B 22.2 A 10.5 B 19.1 A
Ca2+ mmolc dm−3
−15.2 A −28.2 B −17.0 B −10.6 A 0.0 ns −2.2 0.9 A −1.7 B 2.7 A 1.9 B
39.0 38.5 31.0 25.8 20.2 17.6 16.3 17.4 10.3 12.2
ns ns ns ns ns ns ns ns ns ns
−0.2 B 0.3 A −0.4 B 0.2 A −0.2 ns 0.0 ns 0.0 ns 0.2 ns 0.0 ns 0.2 ns
2.5 4.0 – – – – – – – –
Different uppercase letters indicate significant difference between lime treatments within each soil depth by the LSD test at p b 0.01. ns: not significant. – not applicable. a Results of the field experiment represent the difference between the values found before and one year after the lime and gypsum reapplications.
In the field experiment, β-glycosidase activity was significantly increased on topsoil by lime and gypsum treatments, especially in the 0–5 cm layer, in which lime application provided increases of 10.12 g kg−1 h−1 of the enzyme activity (Table 3). On the 10–20 cm layer, we did not observe significant effects. The stocks of HWEOC and POXC were also significantly increased on the topsoil by the Ca-based amendments (Table 3). These increments have driven a significant increase of 0.26 and 0.28 Mg ha−1 of the 0–60 cm accumulated stocks of HWEOC and POXC, respectively. In the laboratory incubation experiment, we observed increases in soil respiration in response to lime and gypsum treatments (Tables 1 and 3). The respiration rates were higher in the first 30 months, and they tended to reduce and become more constant after this initial period (data not shown). The stocks of HWEOC and POXC were also significantly increased in 0.15 and 0.25 Mg ha−1, respectively, due to lime and gypsum applications in the laboratory incubation (Table 3). We have observed linear increases in the short-term gains of HWEOC and POXC stocks in response to gypsum applications with and without lime in the field experiments. Likewise, the same linear increases were observed in the laboratory experiment (Fig. 4). The stocks of HWEOC and POXC were significantly increased by the soil biological attributes and the Ca+2 content in the field and laboratory experiments (Fig. 5). The increment of each mg kg−1 of β-glycosidase activity in the field experiment, contributed with the increase of 0.02 and 0.03 Mg ha−1 of HWEOC and POXC stocks in the 0–20 cm layer, respectively. Likewise, in the laboratory incubation, the increase of each g kg− 1 of soil respiration, promoted the increment of 0.63 and 0.39 Mg ha− 1 of HWEOC and POXC stocks on the evaluated layer of 0–5 cm. For the Ca2 + in the field experiment, the increase of each mmolc dm− 3 resulted in an increment of 0.03 Mg ha−1 of HWEOC and POXC stocks. For the incubation experiment, the gains provided by Ca2+ were 0,002 and 0,004 Mg ha−1 for HWEOC and POXC stocks, respectively (Fig. 5). 4. Discussion 4.1. Effects of lime and gypsum on soil fertility and soybean yield The significant improvements on soil fertility quality one year after the lime and gypsum reapplications demonstrate the efficiency of
528
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
Fig. 3. Discriminant analysis of principal components (DACP) for the different lime and gypsum rates (G, Mg ha−1) treatments in the a) field; and b) laboratory; experiments.
both Ca-based soil amendments mainly to increase the Ca2+ and reduce the Al3+ contents. Since the Al3+ values found before the reapplications were low at the topsoil layer of 0–20 cm (i.e. 1.9 and 0.2 mmolc dm−3 for control and SL, respectively), it justifies the lack of significance of lime and gypsum applications on soil surface. However, at the 20–40 and 40–60 cm layers, in which the Al3+ contents were higher (6.0 and 4.2 mmolc dm−3 for control and SL, respectively) lime and gypsum provided significant reductions in their contents. These results agree with Caires et al. (2016), who observed significant increments of Ca2+ contents all along the soil profile and reductions in Al3 + saturation in deeper layers as short term effects of gypsum applications (i.e. one year) combined with nitrogen fertilization. According to the authors, the amelioration of soil fertility in deeper layers can promote better maize root development, and consequently a higher nitrogen use efficiency. Positive effects of lime and gypsum on crop productivity are found overwhelmingly on maize crop or grasses (i.e. Poaceae family) in general (Crusciol et al., 2014; Michalovicz et al., 2014; Pauletti et al., 2014; Zandoná et al., 2015; Caires et al., 2016) while studies showing
significant increases in soybean productivity are more rarely found (Joris et al., 2016). Several reasons are pointed out to explain why cereals and soybeans present different responses to lime and gypsum applications. Root cation exchange capacity (RCEC) is lower for cereal crops such as maize and wheat (i.e. 10–20 cmolc kg−1) when compared with soybean (40–80 cmolc kg−1) (Fernandes and Souza, 2006). The RCEC can affect the plant efficiency in absorbing nutrients by raising the concentration of cations at the root and influencing the relative proportions of ions of different valency at the root (Asher and Ozanne, 1961). In addition, soybean presents a higher sulfur translocation efficiency (Silva et al., 2003) and a capacity of penetrating in acid subsoils (Caires et al., 2008). In this way, cereals tend to respond better to soil changes provided by Ca-based soil amendments applications mainly because they are less efficient than soybean in Ca uptake and sulfur translocation. The leaching and losses of magnesium and potassium due to gypsum applications are also reported by several authors (Michalovicz et al., 2014; Pauletti et al., 2014; Zandoná et al., 2015; Basso et al., 2016). For this reason, lime application has been recommended to be applied
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
529
Table 3 Lime effects in the stocks of SOC pools, accumulated soil respiration and β-glycosidase activity in the field experiment, one year after lime and gypsum reapplications and in the laboratory experiment, after 16 months of incubation. Depth, cm
Lime
Fielda
Laboratory
HWEOC Mg ha 0–5 5–10 10–20 20–40 40–60 0–60
Control SL Control SL Control SL Control SL Control SL Control SL
POXC
−1
0.14 B 0.25 A 0.18 B 0.25 A 0.07 B 0.15 A −0.02 ns −0.03 −0.03 ns −0.03 0.34 B 0.60 A
β-glycosidase g kg
0.21 B 0.27 A 0.08 B 0.21 A 0.25 B 0.31 A 0.11 ns 0.10 0.06 ns 0.11 0.72 B 1.00 A
−1
11.87 B 21.99 A 5.55 B 12.07 A 1.59 ns 3.00 – – – – – –
h
−1
HWEOC Mg ha 1.00 B 1.15 A – – – – – – – – – –
POXC
−1
Respiration g kg−1 day−1
2.73 B 2.98 A – – – – – – – – – –
4.64 B 4.84 A – – – – – – – – – –
Different uppercase letters indicate significant difference between lime treatments within each soil depth by the LSD test at p b 0.01. ns: not significant. HWEOC: hot water extractable organic carbon; POXC: permanganate oxidizable organic carbon; SOC: total organic carbon; RESP: Soil Basal Respiration. a Results of the field experiment represent the difference (Δ) between the values found before and one year after the lime and gypsum reapplications.
together with gypsum to compensate the losses. However, in our study, the Mg contents were higher in control plots all along the soil profile, with higher differences in the soil surface, indicating that the ions may have been translocated to deeper depths. On the other hand, the K+ content was not influenced by lime and gypsum treatments, and we observed slight increases all along the soil profile. Therefore, although the lime and gypsum reapplications resulted in immediate beneficial effects for the soil fertility, it did not reflect in the soybean crop productivity in the short-term experiment. However, significant improvements in the grain and Biomass-C production can be expected throughout the years in response to the soil quality increase, as already demonstrated by the long-term study in this same experimental area (Inagaki et al., 2016). 4.2. Short-term effects of lime on SOC pools on crop fields The results of our study support the use of lime and gypsum as strategies to increase SOC stocks in crop fields. The effects of lime on SOC stocks have been widely discussed in the literature, with studies indicating either losses as gains in function of the technique use (Paradelo et al., 2015). In a recent study developed by Aye et al. (2016) in a sodosol (29% of clay) at Victoria - Australia, the authors found depletion of SOC due to lime applications in a 34-year trial with low Biomass-C input and no effect on a 5-year unimproved pasture. Higher biological activity was pointed out as the main factor for SOC decrease. According to the authors, the Biomass-C input was not sufficient to compensate the losses caused by the increment of microbial activity. On the other hand, in our long-term field study, even with the relatively low Biomass-C input rate, ranging from 2.8 to 3.2 Mg ha−1 year−1, we were able to observe significant increments of SOC pools stocks (very sensitive variables to soil degradation) in response to lime and gypsum applications in this same experimental area (Inagaki et al., 2016). Likewise, significant increase of labile SOC pools and biological activity were observed after short-term evaluation from lime and gypsum reapplications. Since soybean crop yield was not significantly influenced by the treatments, the Biomass-C input may has caused a lower influence over such short-term increases in labile SOC, when compared with the long-term effects. The main factor related to the preservation of SOC stocks either in the field or in the laboratory experiment was the soil biological activity, measured by β-glycosidase activity and soil respiration, respectively. This positive influence of biological variables in the increase of SOC stocks demonstrates that the improvement of soil microbial activity
was not deleterious to the soil health. In addition, calcium ions have been shown an important role in the SOC protection (Briedis et al., 2012b; Inagaki et al., 2016), fact that was also observed in our study, and therefore, it can be a reasonable explanation for the short-term increases. In our long-term field experiment (Inagaki et al., 2016), the net rates of total SOC sequestration provided by surface-lime + gypsum treatments varied from 3.9 to 5.3 Mg ha− 1 year−1 during 15 years from the experiment establishment. In addition, the stocks of labile SOC pools (i.e. HWEOC and POXC) in limed soils were significantly higher than in the control plots. For this short-term evaluation one year after the lime and gypsum reapplications, although we did not observe significant improvements in the total SOC stock, the same was not depleted, as stated in many studies evaluating SOC stocks in response to liming few months or years after the applications. On the other hand, the differences in the labile SOC pools and enzyme activity between limed and non-limed plots were evident even only a year after the reapplications. The HWEOC is a representative of the microbial biomass, since it contains a high presence of microbial derived SOC (Haynes and Francis, 1993). In the same way, POXC stands out as an efficient method to measure labile SOC, once it is highly correlated with microbial biomass and particulate SOC (Culman et al., 2012). Both labile SOC forms together with enzyme activities have been largely used as parameters to evaluate soil quality due to their sensitivity to land use and management changes (Makoi and Ndakidemi, 2008; Uchida et al., 2012; Hurisso et al., 2016). The expressive response of these variables to short-term lime and gypsum application, in this fact emphasizes their capacity to work as soil quality indicators. 4.3. The use of undisturbed soil samples for incubation experiments The positive influences of lime and gypsum applications on the increase of labile SOC pools (i.e. HWEOC and POXC) and the lack of depletion of the total SOC stock in the laboratory incubation experiment support the use of Ca-based soil amendments to provide carbon sequestration and environmental sustainability. The results observed in the incubation experiment confirm the observations detected in our field trial and they go in the opposite direction of the results of Fuentes et al. (2006). Evaluating soil basal respiration in function of liming, the authors found initially higher rates for limed samples. However, a shift occurred after 56 days of incubation, when control samples started presenting higher respiration rates. In this case, since no plant residue was available for the microbes, they immediately started depleting the
530
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
Fig. 4. Increase of hot water extractable organic carbon (HWEOC) and permanganate oxidizable organic carbon (POXC) stocks by gypsum rates with and without liming in the a) field experiment at 0–60 cm layer one year after the lime and gypsum reapplications; and in the b) laboratory experiment after 16 months of incubation. Gains of field experiment represent the difference between the values found before and one year after the lime and gypsum reapplications.
SOC, stimulated by the lime addition. When the substrate availability became scarce in the soil, the microbial activity became lower, the moment that the shift occurred. Therefore, the increase of SOC pools because of the higher microbial activity (i.e. soil respiration) in our experiment may be explained by the addition of crop residues over the soil surface, which has worked as substrate for the microbiota during the experimental period. Such results agree with Wong et al. (2009), who demonstrated higher microbial activity in treatments with gypsum + plant residues addition in an incubation experiment. In our study, such SOC accumulation was favored by the maintenance of soil structure in the undisturbed sample, which allowed the carbon sequestration along time. Although no significant increments of the total SOC were found, longer experimental periods might demonstrate higher differences, as the SOC turnover increases the stocks in the soil due to the biomass-C input (Briedis et al., 2012a). The results obtained from the laboratory incubation are supported by the field experiment, in which we also found increments in labile SOC pools in response to the higher microbial activity (i.e. β-glycosidase activity).
The majority of the studies demonstrating depletion of SOC stocks as a result of liming make use of soil disturbance operations (Caires et al., 2006; Fuentes et al., 2006; Yagi et al., 2014; Aye et al., 2016; Joris et al., 2016). Such soil disturbance provided by lime incorporation causes the breakdown of soil macroaggregates, exposing the previously protected SOC in their inner to decomposition process by the microbial activity (Tivet et al., 2013). Deleterious effects in response of Ca-based soil amendments found under conventional tillage system conditions also corroborates to explain the impact of soil disturbance. West and McBride (2005) highlighted significant amounts of CO2 emitted from lime applications in USA, where a significant part of the agricultural areas are managed under conventional tillage. In the conversion of a pastureland to crop field, Caires et al. (2006) demonstrated decreases of SOC content of a Brazilian Oxisol in response to lime incorporation by soil plowing and harrowing. Likewise, also in a pastureland – crop field conversion, Joris et al. (2016) observed faster neutralization reactions and decreases in SOC due to lime incorporation. In our long-term lime and gypsum field experiment, we demonstrated that lime incorporation can be deleterious to SOC stocks, and because
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
531
Fig. 5. Influence of soil biological attributes (gains in β-glycosidase activity and soil respiration) and Ca+2 content on labile SOC pools (Hot water extractable organic C – HWEOC; and Permanganate oxidizable organic C – POXC) in the a) field experiment one year after the lime and gypsum reapplications; and in the b) laboratory experiment after 16 months of incubation.
of this, the surface-lime application provides in the best alternative for the conversion of pastureland to crop fields (Inagaki et al., 2016). Thus, for laboratory incubation experiments, it is important to evaluate the lime and gypsum influence using undisturbed soil samples. Their use with application of crop residues on soil surface, therefore, is an efficient tool to simulate the effects of lime and gypsum application on conservation agriculture in highly weathered soil. 4.4. Responses of labile SOC pools to gypsum rates in the field and incubation experiment For the gypsum treatments, the linear increases of labile SOC pools were similar to the ones observed in our long-term experiment (Inagaki et al., 2016). However, for the field experiment, the angular coefficients were higher than in the laboratory incubation, demonstrating a higher potential of gypsum to increase SOC in field trials than in soil incubation experiments. Wong et al. (2009), also detected increases in the soil biological quality in function of gypsum + plant residues addition in an incubation experiment. The authors emphasized that the amelioration of
the soil chemical quality may create a more favorable environment for the microbial development. This factor can be one of the main mechanisms to explain gypsum effects either in the field (Inagaki et al., 2016) or in a soil incubation trial (Wong et al., 2009). The gypsum addition in the crop field experiment was a reapplication in the already improved plots by lime and gypsum applications in 1998. This fact may had contributed for the higher field responses when compared to the laboratory incubation experiment, once soils with higher fertility levels present a higher SOC accumulation efficiency (Briedis et al., 2016). Another factor that could possibly influence the gypsum effects in the field experiment is the presence of plants and their root system in the soil profile. According to Caires et al. (2016), the gypsum application can favor the plants root growth, mainly in response to Ca2 + increment along the soil profile. Since the plant roots are recognized as a source of SOC (Johnson et al., 2006), and they can act as an important soil aggregation agent (Rillig et al., 2015), modifications of the SOC stocks in response to gypsum addition may be likely related to changes in their properties or distribution along the soil profile. Therefore, more studies relating the modifications in the root system and its properties in response to
532
T.M. Inagaki et al. / Science of the Total Environment 599–600 (2017) 523–532
gypsum application can contribute to understand more its effect on SOC sequestration. 5. Conclusions We conclude that lime and gypsum applications can highly increase soil microbial activity and stocks of labile SOC pools in long-term no-till system. We demonstrated that although the soil microbial activity is highly increased after 1 and 1.5 years from the applications (field and laboratory experiments, respectively), it does not lead to SOC depletion on conservation agriculture. The increase of soil biological activity and Ca2 + contents were the main factors governing the increase of SOC stocks. The laboratory incubation experiment confirmed the results obtained in the field, and it has demonstrated to be an efficient way to simulate no-till conditions. Our finds open opportunities for the development of new projects to simulate no-till conditions under controlled conditions. Funding This work was supported by CNPq (Grant 482292/2012-1) and CAPES (Grant 99999.006792/2014-06) for research funding and the scholarship for corresponding author and CNPq grant 304945/2013-7 for a scholarship to the third author. Acknowledgments We would like to thank CAPES for providing the first author with a scholarship and the Laboratório de Matéria Orgânica do Solo (LABMOS) of the State University of Ponta Grossa for providing the structure to develop the soil analyses for this study. References Araújo, L.G., 2016. Uso do gesso e sua influência na produção de cana-de-açúcar, atributos químicos e estoque de carbono no solo de cerrado. Faculdade de Agronomia e Medicina Veterinária. Universidade de Brasília, p. 101. Asher, C.J., Ozanne, P.G., 1961. The cation exchange capacity of plant roots, and its relationship to the uptake of insoluble nutrients. Aust. J. Agric. Res. 12 (5), 755–766. Aye, N.S., Sale, P.W., Tang, C., 2016. The impact of long-term liming on soil organic carbon and aggregate stability in low-input acid soils. Biol. Fertil. Soils 1–13. Basso, C.J., Somavilla, L., da Silva, R.F., Santi, A.L., 2016. Intervenção mecânica e gesso agrícola para mitigar o gradiente vertical de cátions sob sistema de plantio direto. Pesquisa Agropecuária Tropical (Agricultural Research in the Tropics) 45, 456–463. Briedis, C., Sá, J.C.d.M., Caires, E.F., de Fátima Navarro, J., Inagaki, T.M., Boer, A., de Oliveira Ferreira, A., Neto, C.Q., Canalli, L.B., Bürkner dos Santos, J., 2012a. Changes in organic matter pools and increases in carbon sequestration in response to surface liming in an Oxisol under long-term no-till. Soil Sci. Soc. Am. J. 76, 151–160. Briedis, C., Sá, J.C.d.M., Caires, E.F., Navarro, J.d.F., Inagaki, T.M., Boer, A., Neto, C.Q., Ferreira, A.d.O., Canalli, L.B., Santos, J.B.d., 2012b. Soil organic matter pools and carbonprotection mechanisms in aggregate classes influenced by surface liming in a no-till system. Geoderma 170, 80–88. Briedis, C., Sá, J.C.d.M., Lal, R., Tivet, F., de Oliveira Ferreira, A., Franchini, J.C., Schimiguel, R., da Cruz Hartman, D., dos Santos, J.Z., 2016. Can highly weathered soils under conservation agriculture be C saturated? Catena 147, 638–649. Caires, E., Barth, G., Garbuio, F., 2006. Lime application in the establishment of a no-till system for grain crop production in Southern Brazil. Soil Tillage Res. 89, 3–12. Caires, E., Pereira Filho, P., Zardo Filho, R., Feldhaus, I., 2008. Soil acidity and aluminium toxicity as affected by surface liming and cover oat residues under a no-till system. Soil Use Manag. 24, 302–309. Caires, E., Haliski, A., Bini, A., Scharr, D., 2015. Surface liming and nitrogen fertilization for crop grain production under no-till management in Brazil. Eur. J. Agron. 66, 41–53. Caires, E.F., Zardo Filho, R., Barth, G., Joris, H.A., 2016. Optimizing nitrogen use efficiency for no-till corn production by improving root growth and capturing NO 3-N in subsoil. Pedosphere 26, 474–485. Chan, K., Heenan, D., 1999. Lime-induced loss of soil organic carbon and effect on aggregate stability. Soil Sci. Soc. Am. J. 63, 1841–1844. Crusciol, C.A.C., Foltran, R., Rossato, O.B., McCray, J.M., Rossetto, R., 2014. Effects of surface application of calcium-magnesium silicate and gypsum on soil fertility and sugarcane yield. Rev. Bras. Ciênc. Solo 38, 1843–1854. Culman, S.W., Snapp, S.S., Freeman, M.A., Schipanski, M.E., Beniston, J., Lal, R., Drinkwater, L.E., Franzluebbers, A.J., Glover, J.D., Grandy, A.S., 2012. Permanganate oxidizable carbon reflects a processed soil fraction that is sensitive to management. Soil Sci. Soc. Am. J. 76, 494–504.
Curtin, D., Beare, M.H., Hernandez-Ramirez, G., 2012. Temperature and moisture effects on microbial biomass and soil organic matter mineralization. Soil Sci. Soc. Am. J. 76, 2055–2067. Embrapa, 2013. Sistema Brasileiro de Classificação de Solos - SiBCS (3ª edição). Centro Nacional de Pesquisa de Solos, Rio de Janeiro. Fernandes, M., Souza, S., 2006. Absorção de nutrientes. Nutrição mineral de plantas. Sociedade Brasileira de Ciência do Solo, Viçosa, pp. 115–152. Ferreira, D., 2008. Programa Sisvar, versão 5.1: programa de análises estatísticas. DEX/ UFLA, Lavras. Fuentes, J.P., Bezdicek, D.F., Flury, M., Albrecht, S., Smith, J.L., 2006. Microbial activity affected by lime in a long-term no-till soil. Soil Tillage Res. 88, 123–131. Ghani, A., Dexter, M., Perrott, K., 2003. Hot-water extractable carbon in soils: a sensitive measurement for determining impacts of fertilisation, grazing and cultivation. Soil Biol. Biochem. 35, 1231–1243. Haynes, R., Francis, G., 1993. Changes in microbial biomass C, soil carbohydrate composition and aggregate stability induced by growth of selected crop and forage species under field conditions. J. Soil Sci. 44, 665–675. Hurisso, T.T., Culman, S.W., Horwath, W.R., Wade, J., Cass, D., Beniston, J.W., Bowles, T.M., Grandy, A.S., Franzluebbers, A.J., Schipanski, M.E., 2016. Comparison of permanganate-oxidizable carbon and mineralizable carbon for assessment of organic matter stabilization and mineralization. Soil Sci. Soc. Am. J. 80, 1352–1364. Inagaki, T.M., Sá, J.C.d.M., Caires, E.F., Gonçalves, D.R.P., 2016. Lime and gypsum application increases biological activity, carbon pools, and agronomic productivity in highly weathered soil. Agric. Ecosyst. Environ. 231, 156–165. Jenkinson, D., Powlson, D.S., 1976. The effects of biocidal treatments on metabolism in soil—V: a method for measuring soil biomass. Soil Biol. Biochem. 8, 209–213. Johnson, J.-F., Allmaras, R., Reicosky, D., 2006. Estimating source carbon from crop residues, roots and rhizodeposits using the national grain-yield database. Agron. J. 98, 622–636. Joris, H.A.W., Caires, E.F., Scharr, D.A., Bini, Â.R., Haliski, A., 2016. Liming in the conversion from degraded pastureland to a no-till cropping system in Southern Brazil. Soil Tillage Res. 162, 68–77. Makoi, J.H., Ndakidemi, P.A., 2008. Selected soil enzymes: examples of their potential roles in the ecosystem. Afr. J. Biotechnol. 7. Michalovicz, L., Müller, M.M.L., Foloni, J.S.S., Kawakami, J., Nascimento, R.d., Kramer, L.F.M., 2014. Soil fertility, nutrition and yield of maize and barley with gypsum application on soil surface in no-till. Rev. Bras. Ciênc. Solo 38, 1496–1505. Nelson, D.W., Sommers, L.E., 1996. Total carbon, organic carbon and organic matter. Method of soil analysis: chemical methods. Soil Sci. Soc. Am. J. 961–1010. Paradelo, R., Virto, I., Chenu, C., 2015. Net effect of liming on soil organic carbon stocks: a review. Agric. Ecosyst. Environ. 202, 98–107. Pauletti, V., Pierri, L.d., Ranzan, T., Barth, G., Motta, A.C.V., 2014. Efeitos em longo prazo da aplicação de gesso e calcário no sistema de plantio direto. Rev. Bras. Ciênc. Solo 38, 495–505. Pavan, M.A., Bloch, M.d.F., Zempulski, H.d.C., 1992. Manual de análise química de solo e controle de qualidade. IAPAR. Peel, M.C., Finlayson, B.L., McMahon, T.A., 2007. Updated world map of the Köppen-Geiger climate classification. Hydrol. Earth Syst. Sci. Discuss. 4, 439–473. R Development Core Team, 2014. R: a language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing; 2012. Open access available at. http://cran.r-project.org. Rillig, M.C., Aguilar-Trigueros, C.A., Bergmann, J., Verbruggen, E., Veresoglou, S.D., Lehmann, A., 2015. Plant root and mycorrhizal fungal traits for understanding soil aggregation. New Phytol. 205, 1385–1388. Sá, J.C.d.M, Bürkner dos Santos, J., Lal, R., De Moraes, A., Tivet, F., Sá, M.F.M., Briedis, C., de Oliveira Ferreira, A., Eurich, G., 2013. Soil-specific inventories of landscape carbon and nitrogen stocks under no-till and native vegetation to estimate carbon offset in a subtropical ecosystem. Soil Sci. Soc. Am. J. 77, 2094–2110. Silva, D.J., Venegas, V.H.A., Ruiz, H.A., Sant'Anna, R., 2003. Translocação e redistribuição de enxofre em plantas de milho e de soja. Pesq. Agropec. Bras., Brasília 38, 715–721. Survey Staf, Soil, 2010. Keys to Soil Taxonomy. 11th ed. United States Department of Agriculture -Natural Resources Conservation Service, Washington, DC. Tirol-Padre, A., Ladha, J.K., 2004. Assessing the reliability of permanganate-oxidizable carbon as an index of soil labile carbon. Soil Sci. Soc. Am. J. 68, 969–978. Tivet, F., Sá, J.C.d.M., Lal, R., Briedis, C., Borszowskei, P.R., dos Santos, J.B., Farias, A., Eurich, G., da Cruz Hartman, D., Junior, M.N., 2013. Aggregate C depletion by plowing and its restoration by diverse biomass-C inputs under no-till in sub-tropical and tropical regions of Brazil. Soil Tillage Res. 126, 203–218. Uchida, Y., Nishimura, S., Akiyama, H., 2012. The relationship of water-soluble carbon and hot-water-soluble carbon with soil respiration in agricultural fields. Agric. Ecosyst. Environ. 156, 116–122. West, T.O., McBride, A.C., 2005. The contribution of agricultural lime to carbon dioxide emissions in the United States: dissolution, transport, and net emissions. Agric. Ecosyst. Environ. 108, 145–154. Wong, V.N., Dalal, R.C., Greene, R.S., 2009. Carbon dynamics of sodic and saline soils following gypsum and organic material additions: a laboratory incubation. Appl. Soil Ecol. 41, 29–40. Wyngaard, N., Echeverría, H.E., Rozas, H.R.S., Divito, G.A., 2012. Fertilization and tillage effects on soil properties and maize yield in a Southern Pampas Argiudoll. Soil Tillage Res. 119, 22–30. Yagi, R., Fidalski, J., Tormena, C.A., 2014. A incorporação de calcário em sistema plantio direto consolidado reduz o estoque de carbono em macroagregados do solo. Ciênc. Rural 44, 1962–1965. Zandoná, R.R., Beutler, A.N., Burg, G.M., Barreto, C.F., Schmidt, M.R., 2015. Gesso e calcário aumentam a produtividade e amenizam o efeito do déficit hídrico em milho e soja. Pesquisa Agropecuária Tropical (Agricultural Research in the Tropics) 45.