Tillage effects on soil physical condition and root growth associated with sugarcane water availability

Soil & Tillage Research 187 (2019) 110–118

Contents lists available at ScienceDirect

Soil & Tillage Research journal homepage: www.elsevier.com/locate/still

Tillage effects on soil physical condition and root growth associated with sugarcane water availability

T

⁎

Fábio Vale Scarparea,b, , Quirijn de Jong van Liera, Larissa de Camargoc, R.C.M. Piresc, Simone Toni Ruiz-Corrêad, A.H.F. Bezerraa, G.J.C. Gavae, C.T.S. Diasd a

Centro de Energia Nuclear na Agricultura (CENA), Universidade de São Paulo (USP), Av. Centenário, 303, 13416-000, Piracicaba, SP, Brazil Faculdade de Engenharia Mecânica (FEM), Universidade Estadual de Campinas (UNICAMP), Cidade Universitária “Zeferino Vaz”, 13083-860, Campinas, SP, Brazil c Instituto Agronômico de Campinas (IAC), Av. Barão de Itapura, 13012-970, Campinas, SP, Brazil d Universidade de São Paulo (USP), Escola Superior de Agricultura “Luiz de Queiroz” (ESALQ), Av. Pádua Dias, 11, 13418-900, Piracicaba, SP, Brazil e Instituto Agronômico de Campinas (IAC), Experimental Station, Rodovia SP-304 km, 304, 17201-970, Jaú, SP, Brazil b

A R T I C LE I N FO

A B S T R A C T

Keywords: In-row deep tillage Bulk density Root assessment Soil water content Total available water

We hypothesized that in-row deep tillage (DT) may improve crop resilience during dry spells through change in the soil physical/hydraulic properties, in root system development and yield. The objective of this study was to gain insight into the influence of this management on soil physical properties and root growth associated with sugarcane water availability. A three-year experiment on a sandy-clay haplustox was used for the assessment of water retention, bulk density, porosity, pressure head, temperature and plant response (yield and root system). Soil carbon stocks were also assessed in the soil profile. The treatments compared of conventional tillage (CT), which consisted of a 0.3 m ploughing followed by two disking graders with 20″ discs and one light disking leveler grade, and DT, a subsoiler rod (0.8 m deep) with a rotary hoe with 16 knives to raise crop seedbed in rows. Our results reveal that DT resulted in lower bulk density and higher total porosity values than CT in most cases for the surface soil layers. Moreover, while the soil water relations did not show significant difference for total water availability, the soil water pressure head monitoring indicated a trend of more negative values under CT management, i.e., a drier condition. Additionally, DT resulted in better root system development referring to root density and root length density. However, DT resulted in lower sugarcane yield. The experiment was carried out under rainfed conditions, but rainfall distribution did not limit sugarcane production. Therefore, under the mild water stress conditions as observed in this study, the observed root biomass increase did not favor sugarcane yield.

1. Introduction

development, gas exchange properties, nutrient availability and soil hydraulic properties (Laclau and Laclau, 2009). Therefore, altered tillage practices could affect soil water infiltration and retention, depending on the level of soil disturbance (Blanco-Canqui et al., 2017). When establishing new sugarcane fields, tillage is performed to create favorable physical conditions for plant emergence and root growth (Chopart et al., 2008). Tillage is an expensive operation, representing about 25% of the total sugarcane production cost (Silva Júnior et al., 2013). Hence, successful crop establishment determines economic return for several years, while failure requires significant further cost in replanting (Baracat-Neto et al., 2017; Braunack and McGarry, 2006). Depending on soil characteristics like texture, organic matter (OM) and water content, the depth of tillage/soil mobilization

Sugarcane is a semi-perennial ratoon crop harvested yearly. Under rainfed condition, crop fields need to be replanted after four or five ratoons because of yield decline (Braunack and McGarry, 2006; Scarpare et al., 2016) caused mainly due to rhizome damages during harvesting (van Antwerpen et al., 2000) and excessive haulage causing soil compaction (Chopart et al., 2010). In Brazil, the traditional manual harvesting of burnt cane has been replaced by green (unburnt) cane management using harvesting machines (Leal et al., 2013). Although changes in soil physical properties do not necessarily result in yield reduction (van Antwerpen et al., 2000), soil compaction reduces macroporosity, an important parameter affecting root

⁎ Corresponding author at: Centro de Energia Nuclear na Agricultura (CENA), Universidade de São Paulo (USP), Av. Centenário, 303, 13416-000, Piracicaba, SP, Brazil. E-mail address: [email protected] (F.V. Scarpare).

https://doi.org/10.1016/j.still.2018.12.005 Received 1 August 2018; Received in revised form 30 November 2018; Accepted 4 December 2018 0167-1987/ © 2018 Elsevier B.V. All rights reserved.

Soil & Tillage Research 187 (2019) 110–118

F.V. Scarpare et al.

and the type of implement used, tillage may be accompanied by unwanted changes. For example, it may be associated with surface erosion, especially in combination with erosive precipitation events (Sparovek and Schnug, 2001). Moreover, the disturbance of soil aggregates and the subsequent exposure of organic material to decomposing biota has been associated to the loss of OM from the topsoil, reducing soil carbon sequestration (Galdos et al., 2009; Baker et al., 2007). The repeated plowing in conventional tillage commonly results in the formation of dense plough pans that may seriously affect root growth (Marasca et al., 2015; de Maria et al., 1999). Subsoiling may alleviate the problem, increasing crop yield by increasing infiltrability and water storage and by increasing the root depth and subsequent water and nutrient uptake (Lampurlanés et al., 2001). In this context, in-row deep tillage has been adopted in several commercial sugarcane fields in Brazil aiming to reduce bulk density and increase total porosity, allowing an increase of the root system hence, plant available water (PAW, mm) and, supposedly, yield. However, measured effects of deep tillage management in sugarcane field trials on soil physical properties and the observed yield response show that the involved mechanisms are complex and sensitive to many factors (Kumar et al., 2012; Marasca et al., 2015; van Antwerpen et al., 2000). Since each tillage system has both advantages and drawbacks that may depend on soil and climate, field trials addressing several quantitative and qualitative aspects of tillage management are necessary for a broad overview of strategies for sustainability production. We hypothesized that the in-row deep tillage increases the crop resilience to cope with dry spells by changing the soil physical/hydraulic properties, also affecting root system development. Therefore, this management practice may contribute to biomass production in rainfed agriculture with drought risks, i.e., in those areas where the water regime may be unfavorable for sugarcane development. In this context, the objective of this study was to gain insight into the influence of tillage management on soil physical properties and root growth and their association with sugarcane water availability and yield.

Fig. 1. Subsoiler rod (0.8 m) with a rotary hoe (16 knives with 0.3 - 0.4 m working depth and a bar width of 1.2 m) of the in-row deep tillage equipment (left) and seedbed formation in rows (right).

lime was applied (2.5 Mg ha−1, 80% of effective neutralizing power) and incorporated down to 0.2 m depth in the entire area using a 12 discs harrow of 22″. In mid-December 2014, under adequate soil moisture conditions for machine trafficability, the sugarcane variety IACSP 95–5000 was planted with 15 buds m-1, 0.2 m deep under two tillage systems; Conventional Tillage (CT) and In-row Deep Tillage (DT), arranged in a randomized split block design with 0.3 ha each (57 x 58 m). CT is the business-as-usual adopted in Brazilian sugarcane fields, which consists in the use of a 0.3 m ploughing followed by two disking graders, with 20″ discs and one light disking leveler grade. DT was performed using a subsoiler rod (0.8 m deep) with a rotary hoe with 16 knives (0.3 - 0.4 m working depth and a bar width of 1.2 m) to break the soil crust and a system to raise crop rows, seedbed formation in rows (Fig. 1). Due to the implement characteristics, dual rows with 1.5 m between duals spaced 0.9 m apart were adopted (Fig. 2A) using a double trencher. In the planting furrow, 150 kg ha−1 of P2O5 as triple superphosphate source was applied while 140 kg ha−1 of N and 150 kg ha−1 of K2O were subdivided in two applications, at one and three months after planting. The same procedure of N and K2O applications type was repeated for first ratoon crop. Pests, diseases and weeds were controlled to negligible levels.

2.2. Sampling, measurements and data analysis

2. Material and methods

The soil-water retention characteristics were measured from undisturbed cores collected with stainless steel cylinders (0.05 x 0.05 m) at 0.20, 0.40 and 1.0 m depths with ten replicates. All field assessments were carried out after a rainy period (soil pressure head ∼ −1 m) to facilitate soil handling. Besides the analysis between tillage treatments, the soil physical/hydraulic properties monitoring on a temporal basis across seasons is needed to better characterize tillage effects. Therefore, the sampling and evaluations were carried out four times, first during fallow (May/2014), then during plant cane (Pl – year 1), first ratoon (R1 – year 2) and second ratoon (R2 – year 3) (Fig. 2B). In this study, Pl, R1 and R2 are designated as crop cycles and used as a time-related factor in the statistical analyses. During fallow, soil samples were randomized over the area, but after planting (Dec/2014) samples were randomly collected between sugarcane dual rows. Shortly after planting, dielectric water potential sensors (MPS-2 Decagon, Pullman, USA) were horizontally installed at the same depths used for soil undisturbed samples, i.e., at 0.2, 0.4 and 1.0 m depths, 0.15 m apart from the planted lines with three replicates (Fig. 2A), recording soil water pressure head and soil temperature data every fifteen minutes (Fig. 2B). Air temperature (HMP155 Vaisala, Helsinki, Finland) and rainfall (ECRN-100 Decagon, Pullman, USA) were also record every fifteen minutes by a meteorological station installed adjacent to the experimental area. In the laboratory, undisturbed soil cores were saturated and then equilibrated to defined pressure heads (-0.1, -0.2, -0.6, -1.0, -3.3, -10, -30 and -150 m) on a porous plate pressure chamber equipment, after which water content was determined. The van Genuchten (1980) soilwater retention equation was fitted to these data to describe the

2.1. Site description and experimental design A three-year experiment was carried out at the Experimental Station of the Agronomic Institute of Campinas (IAC), located at 22°17′ S, 48°34′ W, and 580 m, in the municipality of Jaú, State of São Paulo, Brazil. The climate in this traditional sugarcane region is classified as Köppen Aw, mesothermal tropical, with a mean annual temperature of 24.0 °C and mean annual precipitation of ∼1300 mm. The soil of the experiment field is a haplustox according to the USDA taxonomy, with a sandy clay texture (Table 1). It has been used for sugarcane cultivation for more than 20 years, without the application of vinasse. Before field trial establishment, remaining rhizomes from the last ratoon were removed by manually hoeing. Subsequently, a fallow period of twelve months was established. Three months before planting, Table 1 Particle size distribution of the haplustox soil at the experimental area. Particle-size distribution (%) Depth (m)

0.2 0.4 1.0

Coarse Sand

Fine Sand

Silt

Clay

2.0 – 0.2 mm 5.3 4.0 5.1

0.2 – 0.05 mm 52.8 47.2 50.1

0.05 – 0.002 mm 5.8 5.5 4.9

< 0.002 mm 36.2 43.4 39.9

Bulk density* g cm−3

1.67 1.53 1.48

* Performed during fallow period. 111

Soil & Tillage Research 187 (2019) 110–118

F.V. Scarpare et al.

Fig. 2. Schematic overview of the field trial showing row distances and depths of soil water pressure head sensors in DT and CT treatments (A) and the experimental timeline with agricultural operations, sampling and periods of measurement of temperature and pressure head (B).

functional relationship between predicted soil water content θ(h) and the corresponding absolute value of the pressure head (h). Soil bulk density (ρ) was determined after drying the soil at 105 °C for 24 h while particle density (ρp) was determined by the pycnometer method resulting in 2708, 2679 and 2670 kg m−3 for 0.2, 0.4 and 1.0 m soil depths respectively. Soil porosity (α) was calculated from bulk and particle densities. The volume fraction of micropores was estimated considering the water content at 0.6 m tension (θ0.6) and macropore content by the difference between micropores and α. Moreover, the total available water (TAW, mm m-1), defined as the water storage between field capacity (θfc) and permanent wilting point (θpwp) was estimated for three soil layers (0-0.3, 0.3-0.6 and 0.6–1.0 m) considering field capacity and permanent wilting point to correspond to pressure heads of -1.0 and -150 m respectively. The readily available water (RAW, mm m-1), defined as the water storage between field capacity (θfc) and critical water content (θcr) of ∼ 0.3 m3 m-3 was estimated using hcr = -10 m as critical pressure head for sugarcane (Allen et al., 1998). Sugarcane yield, i.e., fresh millable stalk mass (Mg ha−1) was determined by manually harvesting without the burning of straw for Pl (first harvest) and R1 (second harvest) cycles. Nevertheless, inevitably some machinery traffic during hauling occurred. The sugarcane root system was assessed 174 days after the second harvest, during R2 (Fig. 2B) by the trench-profile method by grid root interception counting (RI, m−2) (Tennant, 1975). This period was chosen since it coincides to the end of intense tillering / beginning of the stem growth phases, which represents the maximum cumulative root density for sugarcane crops (Ohashi et al., 2015). Both treatments used three trenches 1.5 m-long × 2 m-deep as replicates, which were randomly excavated perpendicularly to the sugarcane rows using one dual row in each plot (Fig. 3). After preparation of the trench face, white spray paint was applied

for better contrast; next, a stainless-steel grid (1.0 m-long × 1.5 mdeep) was fixed for root length (RL, cm) estimation according to:

RL =

11 × RI × GS 14

(1)

where RI is the number of root interceptions in the grid cell and GS is the grid length cell size (0.025 m), which are multiplied by a constant (11/14) defined by Tennant (1975) for 1 cm grid cell measurement. The 2D root length density (RLD, mm cm−2) was estimated considering the ratio between RL by its occupied area in the soil profile. The Surfer® software (version 9.0, Golden Software Inc., Golden, CO, USA) was used for 2D RLD maps generation with the interpolation of data performed by the kriging method. The root system dry matter (kg m-3) was estimated considering the relationship between the 3D root length density (RLD, m m-3) and the root biomass density (RBD, g m-3) considering the specific root length of 27 m g-1 according to Chopart el al. (2010). The 3D RLD (m m-3) was estimated from root interception (RI) taking root orientations as proposed by Chopart et al. (2008). To find out whether tillage affects the soil organic carbon and its stocks, soil samples taken from each treatment by the end of the experiment (in Mar/2017) were compared with the control, taken during the fallow period almost three years before (in May/2014). The soil carbon (C) stock (Mg ha−1) was calculated from bulk density and the total carbon concentration for each layer (0-0.1, 0.1-0.2, 0.2-0.4, 0.40.6, 0.6-0.8 and 0.8–1.0 m). Soil total C determination was made in air dried soil samples sieved through a 100 mesh and measured by dry combustion in an elemental analyzer (LECO © TrustPec, Michigan, USA). For statistical assessment, the soil physical properties in each layer were performed in a 2 × 3 factorial arrangement (soil tillage x plant cycles: Pl, R1 and R2) with 10 replicates. For cane yield, a 2 × 2 factorial arrangement (soil tillage x plant cycles: Pl and R1) with 12 replicates was used while for soil carbon stocks a 3 × 6 factorial 112

Soil & Tillage Research 187 (2019) 110–118

F.V. Scarpare et al.

Fig. 3. Pictures of A - Trench opening; B - Trench face preparation (manual scarification), C - Scarification (soil painted removal) and D - Stainless-steel grid (1.0 mlong × 1.5 m-deep) fixed in trench wall for root length assessment.

significant interactions were found for micropores in the surface layer and for TAW in the bottom layer, 0.6–1.0 m (Table 3). Regarding TAW, several studies highlight that water storage and the response to tillage may be uncertain. In a loam soil type, Brandt (1992) investigated 12 years of CT versus no tillage (NT), and found that NT resulted in a significantly higher soil water content in only 25% of cases. In a clayey Vertisol in Sudan, Hammad and Dawelbeit (2001) did not find any significant TAW differences in sugarcane fields under intensive tillage practices to depths of 0.1, 0.2, and 0.3 m. In our investigation, we also assessed the TAW combining the three assessed layers (0–1.0 m). Although the analysis of variance showed a significant interaction between both factors, the comparison of means reveals that the crop seasonal differences was determinant, not the tillage management (Table 4). The same pattern was observed for the other pressure heads used to build the soil-water retention along the experiment trial (Fig. 4). As the interaction between tillage and crop cycles were found to be not significant (Table 2), for other physical properties both factors were analyzed separately pointing that the effect of the crop season, i.e., on the temporal scale, was striking. This is probably due to the fact that the measurements from the first ratoon (17 months after tillage management) showed significant and consistent differences when compared to the measurements in sugarcane plant (6 months after tillage) and second ratoon (27 months after tillage) cycles (Table 5). Using the dielectric sensors monitoring system, differences in pressure head were observed between both management systems, CT being more negative during drier periods especially in the top layers (Fig. 5). Water contents in the top layers were, however, very similar. This experiment was carried out under rainfed condition, the rainfall distribution (1076 and 1167 mm during plant cane and 1st ratoon cycle respectively) maintained the soil moisture conditions between field capacity and critical water content point most of the time (Fig. 5); suggesting that water availability did not limit cane production. Moreover, most of water deficit took place after the crop establishment phase, which takes about 120 days from emergence. Hence, these differences did not reflect in yield gains, on the contrary; the analysis of variance indicated lower sugarcane yield under DT management with significant difference for the first ratoon cycle (Tables 6 A and 6B). Higher yield was obtained for R1 (second harvest) than for P1, first harvest (Table 6B). This unusual result occurred mainly as consequence of a shorter cropping period during plant cane, imposing restrictions on its productive potential. In a similar experiment performed on a medium sandy Oxisol in Brazil, Marasca et al. (2015) did not find any sugarcane yield increase under in-row deep tillage management when compared to CT. However, some studies (Bell et al., 2003; Silva Júnior et al., 2013) suggest that alternative tillage system that mobilize deeper soil layers could be more productive under drier conditions, since it provides more favorable soil physical conditions for root development. In fact, the root system analysis in our study confirms this, revealing

arrangement (fallow + soil tillage x soil depth) with eight replicates was used. All data were statistically analyzed using the Statistical Analysis System software, version 9.3. The homogeneity of variance was checked and when necessary the data were transformed using the Box and Cox, (1964) optimal potential procedure. The F-test of variance analysis was performed, and the comparison of means was done by the Tukey test (at 5% of probability). Results for soil water pressure head and soil temperature were analyzed by the Mean Absolute deviation (MAd), Root Mean Square deviation (RMSd), determination coefficient (R2) and the bias. 3. Results and discussion Throughout the experiment, field analysis revealed that there were some differences between the soil environments due to tillage management. For some soil physical properties, the analysis of variance pointed significant interaction between tillage management and crop cycles (Table 2). Only bulk density and total porosity had significant interactions between both factors for the first two depths (0.2 and 0.4 m). Although not all differences were statistically significant, DT provided lower bulk density and higher total porosity values than CT in most cases (Table 3). This may possibly be associated to the rupture of soil surface structure resulting from the rotating hoe, which reaches 0.3 - 0.4 m of working depth during the seedbed formation. Under CT management, bulk density values were very close when comparing to those obtained during fallow (Table 1), especially during plant cane cycle. Moreover, Table 2 Analysis of variance (F estimates) for bulk density, microporosity, macroporosity, total porosity and total available water (TAW), according to tillage treatments (conventional tillage and in-row deep tillage) and crop cycles (plant cane, first ratoon and second ratoon). Depth

Bulk density

Microporosity

Macroporosity

Total porosity

TAW

0.2 m Tillage (T) Cycle (C) TxC CV (%) 0.4 m Tillage (T) Cycle (C) TxC CV (%) 1.0 m Tillage (T) Cycle (C) TxC CV (%)

F value 39.33 * 32.70 * 4.48 ** 5.63 F value 0.21 ns 16.33 * 3.90 ** 6.89 F value 0.65 ns 9.17 * 2.71 ns 7.63

F value 1.88 ns 18.00 * 3.69 ** 6.27 F value 0.95 ns 30.12 * 1.97 ns 5.83 F value 0.35 ns 26.81 * 2.08 ns 7.14

F value 19.65 * 30.76 * 2.23 ns 27,6 F value 0.2 ns 18.98 * 1.12 ns 36.36 F value 0.57 ns 6.51 * 2.05 ns 29.62

F value 24.61 * 25.44 * 3.86 ** 7.95 F value 0.05 ns 14.04 * 3.37 ** 9.47 F value 0.58 ns 2.90 ns 1.92 ns 8.58

F value 0.54 ns 2.66 ns 1.10 ns 24.1 F value 0.71 ns 11.10 * 2.97 ns 12.73 F value 0.37 ns 54.70 * 6.24 * 14.37

*, ** and

ns

are significant at 1%, 5% and not significant, respectively. 113

Soil & Tillage Research 187 (2019) 110–118

F.V. Scarpare et al.

Table 3 Interaction for bulk density, microporosity and total porosity, according to soil tillage treatments (conventional tillage – CT and in-row deep tillage – DT) and cycles (plant cane, first ratoon and second ratoon). Bulk density (g cm−3)

Depth 0.2 m Depth 0.4 m Layer 0.6-1.0 m

Microporosity (m3 m−3)

Total porosity (%)

Tillage

Plant cane

1st Ratoon

2rd Ratoon

Plant cane

1st Ratoon

2rd Ratoon

Plant cane

1st Ratoon

2rd Ratoon

CT DT CT DT CT DT

1.66 1.51 1.53 1.51

1.51 1.29 1.45 1.34

1.64 1.58 1.54 1.63

28.88 Aab 30.54 Aa

26.72 Ab 24.94 Ac

29.59 Aa 27.43 Ab

TAW (mm) 55.16 Aa 46.65 Aa

38.25 44.59 43.02 42.98

44.14 52.33 45.92 49.89

39.51 41.53 42.33 39.28

27.62 Ac 26.09 Ab

35.19 Ab 41.96 Aa

Aa Ba Aa Aa

Ab Bb Aa Ab

Aa Aa Aa Aa

Aa Ab Aa Aab

Ba Aa Aa Aa

Aa Ab Aa Ab

Uppercase letters in columns represent the results of the Tukey test (alpha = 0.05) comparing the tillage treatments CT and DT while lowercase letters in the rows are the results of the Tukey test comparing the sugarcane cycles plant, 1st and 2nd ratoon. TAW is total available water.

sugarcane root growth, Ohashi et al. (2015) reported that the highest growth rate (∼80 mm d−1) occurred when the air temperature was between 25–30 °C, which coincided with the intense tillering phenological stage when vigorous root growth is required to support subsequent tiller growth. Although it is difficult to accurately determine the base temperature (Oliveira et al., 2001;, Camargo et al., 1976), studies addressing this subject point to the range of temperatures between 15 - 10 °C. During our field experiment, such low temperatures were never observed. Moreover, results revealed a trend of for temperatures to be higher under CT management (Fig. 5), which did not cause great differences in the thermal time accumulation between tillage treatments (data not shown). Although root growth is associated to an increase of water and nutrient uptake (Marasca et al., 2015; Chopart et al., 2010), a higher root growth rate implies in less assimilates being partitioned to aboveground organs (stem and leaves). In addition, there is a metabolic cost of root maintenance (Ween, 1981). Little is known about the precise partitioning of carbohydrates to the root system in sugarcane (Smith et al., 2015), but maintenance respiration is considered to be linearly related to living organ biomass (Swinnen et al., 1994; Pritchard and Rogers, 2000). In this context, the lack of detailed knowledge does not prevent successful modelling of sugarcane production, suggesting that current estimates of belowground allocation and maintenance in models are adequate. That may lead to conclude that the belowground dry matter increase might not hamper aboveground sugarcane yield under mild water stress conditions. In fact, using the regression analysis proposed by Chopart et al. (2008) and Chopart et al. (2010), the belowground dry matter estimation under DT management reached higher values (∼ 43.0 kg m−3) than under CT management (∼ 17.0 kg m−3), which reinforces the above assumption. In an environmental context, the soil physical disturbance induced for both tillage systems, compared to the fallow period, did not result in

that DT management provided higher 2D RLD values at the end of the rainy period, March/2017 (Fig. 6). The average 2D RLD (mm cm−2) analysis indicated a significant difference of root content between the tillage systems at the depth of 0.4 m (Fig. 6A). This, in turn, reflected in higher root length density values under DT management (Fig. 6C). Moreover, this analysis evidenced a more homogeneous root distribution in the soil profile under DT, mainly down to 0.6 m depth, while under CT management the roots were concentrated near the planting line (Fig. 6B). These results are possibly a consequence of better soil physical properties provided by DT, like the measured lower soil compaction, measured as lower bulk density and higher soil porosity (Table 3). Smith et al. (2015) highlight that root growth responds strongly to the soil environment, creating plasticity in the form and size of the root system. In this sense, soil moisture (estimated through the relationship between soil pressure head and soil moisture content from Fig. 4), although not determinant for yield increase, could be acting in favor for higher root length distribution under DT management. According to Lampurlanés et al. (2001), higher root density in the surface layer is a mechanism adopted by plants that develop in an environment with lower soil moisture supply to allow ready absorption of water after rainfall. Moreover, this restriction might partly result from the higher mechanical resistance to root growth in dry soil layers. Soil temperature is another variable with a close relation to crop development. There is no specific research on the response of sugarcane to soil temperature, but some studies addressed temperature effects indirectly and related to other aspects of the crop production. For example, Fauconnier and Bassereau (1970) stated that highest sugarcane root water uptake was achieved between 28–30 °C reducing drastically below 15 °C. For sugarcane sprout and emergence response, Camargo et al., (1976) determined 19 °C as critical soil temperature and temperatures lower than 10 °C to be harmful to root and shoot growth. For

Table 4 Total available water (TAW, layer 0–1.0 m) assessment: A- Analysis of variance (F estimates) and; B- TAW interaction analysis according to soil tillage treatments (conventional tillage – CT and in-row deep tillage – DT) and crop cycles (plant cane, 1st ratoon and 2rd ratoon). A

F value

Tillage (T) Cycle (C) TxC CV (%)

1.87 ns 31.64 * 3.93 ** 11.36

B

Plant cane (mm)

1st Ratoon (mm)

2nd Ratoon (mm)

CT DT

101.99 Aa 92.68 Aa

72.83 Ab 63.15 Ab

83.73 Ab 89.67 Aa

*, ** and ns indicate a significance at 1%, 5% and not significant, respectively. Uppercase letters in columns represent the results of the Tukey test (alpha = 0.05) comparing the tillage treatments while lowercase letters in rows are the results of the Tukey test comparing the sugarcane cycles. 114

Soil & Tillage Research 187 (2019) 110–118

F.V. Scarpare et al.

Fig. 4. Soil-water contents versus pressure head under conventional (CT) and in-row deep tillage (DT) at defined pressure heads (-0.1, -0.2, -0.6, -1.0, -3.3, -10, -30 and -150 m) and saturation determined on a porous plate pressure chamber equipment. Δ is the CT average value and □ is the DT average value from ten replicates.

due to the sampling protocol analysis, which consists of sampling not deeper than 0.3 m. Although longer-term experiments are needed for better characterization, the results obtained so far (Table 7) make us to suggest that there are no environmental drawbacks in short-term of greenhouse gases emission when performing DT for sugarcane

significant differences in soil C stocks (Table 7A). However, significant differences in soil C stocks were observed for different depths (Table 7B). While it is widely believed that soil disturbance by tillage is a primary cause of soil organic carbon losses (Reicosky, 2003; Lal et al., 1998), Baker et al. (2007) highlighted that these results may be biased

Table 5 Analysis of variance of A- Macroporosity and B- Microporosity, Bulk density and Total Available Water (TAW) analysis according to soil tillage treatments (conventional tillage – CT and in-row deep tillage – DT) and crop cycles (plant cane, 1st ratoon and 2nd ratoon). A Macroporosity (%) – Depth 0.2 m Significant for cycle factor

Significant for tillage treatment

CT DT

12.76 B 19.3 A

B Macroporosity (%) – Depth 0.4 m st

1st Ratoon (%) 22.41 a

Plant cane (%) 11.72 b Microporosity (%) – Depth 0.4 m nd

Plant cane

1 Ratoon

2

12.64 b Macroporosity (%) – Depth 1.0 m Plant cane 14.42 b

21.74 a

10.87 b

1st Ratoon 22.89 a

2nd Ratoon 18.17 ab

Ratoon

2rd Ratoon (%) 12.01 b

TAW (mm) – Layer 0.4-0.6 m st

nd

Plant cane

1 Ratoon

2

Ratoon

30.36 a Microporosity (%) – Depth 1.0 m Plant cane 29.95 a

26.17 b

29.93 a

1st Ratoon 25.39 b

2nd Ratoon 29.99 a

Plant cane

1st Ratoon

2nd Ratoon

25.65 a Bulk density (g cm−3) – Depth 1.0 m Plant cane 1.51 a

19.69 b

21.94 b

1st Ratoon 1.38 b

2nd Ratoon 1.38 b

Uppercase letters on the columns represent the results of the Tukey test (alpha = 0.05) comparing the tillage treatments while lowercase letters on the rows are the results of the Tukey test comparing the sugarcane cycles. TAW is total available water. 115

Soil & Tillage Research 187 (2019) 110–118

F.V. Scarpare et al.

Fig. 5. (A) Pressure head over time, (B) Pressure head in CT versus DT, (C) Soil moisture content (m3 m−3) (D) Air and soil temperature observed in CT and DT over time and (E) Soil temperature observed in CT versus DT. All data from 15 min interval observations for the three assessed depths (0.2, 0.4 and 1.0 m) under conventional (CT) and in-row deep tillage (DT) management and 1:1 dispersion graph.

prevailing during the study period. Therefore, for a more conclusive statement further studies would be needed in drier years, also including other soil types and different sugarcane varieties. In this context, the soil-plant-atmosphere system modeling assessment may be a useful tool to provide further insights related to the partitioning of belowground organs in photoassimilates distribution and to root biomass maintenance. These important aspects should be addressed in future research, since sugarcane crops are expanding in environments where the water balance may be less favorable for cane production, as is the case for the expansion areas in the Cerrado biome in Brazil.

production system. A more complete assessment would have to take into account the fossil fuel emissions from both management systems, as DT consumes approximately 25% more diesel when compared to CT (Raper and Bergtold, 2007). In this field study, DT did not increase the aboveground biomass production, hence, it did not result in increased field income. However, DT improved the top layer (0–20 cm) soil quality (lower bulk density and higher total porosity) allowing better root system development (Fig. 6B and 6C), which seems to be directly related to the rotary hoe effect. In this sense, the use of a subsoiling rod in this tillage system may be more appropriate to be performed in fields with serious soil compaction problems, since it requires a powerful machine to perform this management. The hypothesis that DT increases the crop resilience to cope with dry spells could not be verified, due to the climatic conditions

4. Conclusions This study focused on the comparison of two sugarcane tillage systems and their influence on crop water availability and yield. The 116

Soil & Tillage Research 187 (2019) 110–118

F.V. Scarpare et al.

Table 6 Sugarcane yield assessment: A- Analysis of variance (F estimates) and; B- Sugarcane (fresh millable stalks mass, Mg ha−1) and its interaction analysis according to soil tillage treatments (conventional tillage – CT and in-row deep tillage – DT) and cycles (plant cane and first ratoon). A

F value

Tillage (T) Cycle (C) TxC CV (%)

14.43 * 139.46 * 4.48 ** 15.03

B

Plant cane (Mg ha−1)

1st Ratoon (Mg ha−1)

CT DT

86.29 Ab 78.93 Ab

154.03 Aa 124.88 Ba

*, ** and ns is a significance at 1%, 5% and not significant, respectively. Uppercase letters in columns represent the results of the Tukey test (alpha = 0.05) comparing the tillage treatments while lowercase letters in rows are the results of the Tukey test comparing the sugarcane cycles.

Fig. 6. Sugarcane root system assessment by the trench profile method at 174 days after second harvest under conventional (CT) and in-row deep tillage (DT) management. A) Average 2D root length density (mm cm−2), B) and C) 2D root length density (cm cm−2) maps under CT and DT management respectively. Table 7 Soil carbon stock assessment: A- Analysis of variance (F estimates) and; B- Soil carbon stock (Mg ha−1) interaction analysis according to soil tillage treatments (conventional tillage – CT and in-row deep tillage – DT). A

F value

Treatments (T) Depths (D) TxD CV (%)

1.97 ns 30.48 * 1.28 ns 15.30

B Layers

Fallow (Mg ha−1)

CT (Mg ha−1)

DT (Mg ha−1)

0-0.1 0.1-0.2 0.2-0.4 0.4-0.6 0.6-0.8 0.8-1.0

22.20 16.50 24.72 18.66 17.85 15.85

22.98 19.43 25.20 20.07 18.95 16.44

19.88 16.66 27.57 20.86 17.73 14.64

AB C A BC BC C

AB BC A BC BC C

B BC A B BC C

*, ** and ns indicates significance at 1%, 5% and not significant, respectively. Uppercase letters in columns represent the results of the Tukey test (alpha = 0.05) comparing the soil depths.

field analysis revealed some differences between the soil physical properties as a result of tillage practices. No difference in total available water could be shown between treatments, but in the upper soil layers DT led to lower bulk density and higher porosity than CT, as a result of deep soil mobilization performed by the DT management. As a consequence, root development was more abundant in DT. In our

experiment with only mild water stress, observed alterations in bulk and rooting density did not result in an increase in aboveground yield. Increase in root biomass may have hampered aboveground yield, while not leading to a significant reduction in drought stress. Therefore, the advantage of DT management, potentially improving soil physical properties for rooting, did not result in an increase in sugarcane yield in 117

Soil & Tillage Research 187 (2019) 110–118

F.V. Scarpare et al.

this rainfed agriculture scenario with moderate drought stress only.

properties, cane and sugar yields in vertisols of Kenana sugar estate, Sudan. Soil Tillage Res. 62, 101–109. Kumar, S., Saini, S.K., Bhatnagar, A., 2012. Effect of subsoiling and preparatory tillage on sugar yield, juice quality and economics of sugarcane (Saccharum species hybrid) in Sugarcane Plant-Ratoon Cropping System. Sugar Tech. 14, 398–404. Laclau, P.B., Laclau, J.P., 2009. Growth of the whole root system for a plant crop of sugarcane under rainfed and irrigated environments in Brazil. Field Crops Res. 114, 351–360. Lal, R., Kimble, J.M., Follett, R.F., Cole, C.V., 1998. The Potential of U.S. Croplands to Sequester Carbon and Mitigate the Greenhouse Effect. Ann Arbor Press, Ann Arbor, MI, pp. 128. Lampurlanés, J., Angás, P., Cantero-Martínes, C., 2001. Root growth, soil water content and yield of barley under different tillage systems on two soils in semiarid conditions. Field Crops Res. 69, 27–40. Leal, M.R.L.V., Galdos, M.V., Scarpare, F.V., Seabra, J.E.A., Walter, A., Oliveira, C.O.F., 2013. Sugarcane straw availability, quality, recovery and energy use: a literature review. Biomass Bioenergy 53, 11–19. Marasca, I., Lemos, S.V., Silva, R.B., Guerra, S.P.S., Lanças, K.P., 2015. Soil compaction curve of an Oxisol under sugarcane planted after in-row deep tillage. R. Bras. Ci. Solo 39, 1490–1497. Ohashi, A.Y.P., Pires, R.C.M., Ribeiro, R.V., Silva, A.L.B.O., 2015. Root growth and distribution in sugarcane cultivars fertigated by a subsurface drip system. Bragantia 74 (2), 131–138. Oliveira, J.C.M., Timm, L.C., Tominaga, T.T., Cassaro, F.A.M., Reichardt, K., Bacchi, O.O.S., Dourado-Neto, D., Câmara, G.M.S., 2001. Soil temperature in a sugar-cane crop as a function of the management System. Plant Soil 230, 61–66. Pritchard, S.G., Rogers, H.H., 2000. Spatial and temporal deployment of crop roots in CO2-enriched environments. New Phytol. 147 (1), 55–71. Raper, R.L., Bergtold, J.S., 2007. In-row subsoiling: a review and suggestions for reducing cost of this conservation tillage operation. Appl. Eng. Agric. 23, 463–471. Reicosky, D.C., 2003. Tillage-induced CO2 emissions and carbon sequestration: effect of secondary tillage and compaction. In: Garcia-Torres, L., Benites, J., Martinez-Vilela, A., Holgado-Cabrera, A. (Eds.), Conservation Agriculture. Kluwer Acad. Pub., Dordrecht, The Netherlands, pp. 291–300. Scarpare, F.V., Hernandes, T.A.D., Ruiz-Corrêa, S.T., Kolln, O.T., Gava, G.J.C., Santos, L.N.S., Victoria, R.L., 2016. Sugarcane water footprint under different management practices in Brazil: tietê/Jacaré watershed assessment. J. Clean. Prod. 112, 4576–4584. Silva Júnior, C.A., Carvalho, L.A., Centurion, J.F., Oliveira, E.C.A., 2013. Comportamento da cana-de-açúcar em duas safras e atributos físicos do solo, sob diferentes tipos de preparo. Biosci. J. 29, 1489–1500. Smith, D.M., Inman-Bamber, N.G., Thorburn, P.J., 2015. Growth and function of the sugarcane root system. Field Crops Res. 92, 169–183. Sparovek, G., Schnug, E., 2001. Soil tillage and precision agriculture, a theoretical case study for soil erosion control in Brazilian sugar cane production. Soil Tillage Res. 61, 47–53. Swinnen, J., van Veen, J.A., Merckx, R., 1994. Rhizosphere carbon fluxes in field-grown spring wheat: model calculations based on 14C partitioning after pulse-labelling. Soil Biol Biochem. 26 (2), 171–182. Tennant, D.A., 1975. Test of a modified line intersect method of estimating root length. J. Ecol. 63, 995–1001. van Antwerpen, R., Meyer, J.H., Meyer, E., 2000. Soil compaction in the South African sugar industry – a review. Proc. S. Afr. Sug. Technol. Ass. 101–108. van Genuchten, M.T., 1980. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Sci. Soc. Am. J. 44, 892–898. Ween, B.W., 1981. Relation between root respiration and root activity. Plant Soil 63, 73–76.

Acknowledgements This study was performed as part of three projects: FAPESP (2016/ 09133-1), CNPq (407258/2013-2) and CNPq (404245/2013-7). Furthermore, support for the fieldwork was provided by the Jaú Experimental Station of the Agronomic Institute of Campinas (IAC) and the laboratorial support was provided by the Centro de Energia Nuclear na Agricultura (CENA-USP) - Laboratório de Física de Solo (FISOL). References Allen, R.G., Pereira, L.S., Raes, D., Smith, M., 1998. Crop Evapotranspiration-Guidelines For Computing Crop Water Requirements-FAO Irrigation and Drainage Paper 56. FAO, Rome 300(9), D05109. Baker, J.M., Ochsner, T.E., Venterea, R.T., Griffis, T.J., 2007. Tillage and soil carbon sequestration - what do we really know? Agric. Ecosyst. Environ. Appl. Soil Ecol. 118, 1–5. Baracat-Neto, J., Scarpare, F.V., Araújo, R.B., Scarpare-Filho, J.A., 2017. Initial development and yield in sugarcane from different propagules. Pesq. Agropec. Trop. 47, 273–278. Bell, M.J., Halpin, N.V., Garside, A.L., Moody, P.W., Stirling, G.R., Robotham, B.J., 2003. Evaluating combinations of fallow management, controlled traffic and tillage options in prototype sugarcane farming systems at bundaberg. Proc. Conf. Aust. Soc. Sugar Cane Technol. 26 ISSN 0726-0822. Blanco-Canqui, H., Wienhold, B.J., Jin, V.L., Schmer, M.R., Kibet, L.C., 2017. Long-term tillage impact on soil hydraulic properties. Soil Tillage Res. 170, 38–42. Box, G.E., Cox, D.R., 1964. An analysis of transformations. J. R. Stat. Soc. Series B Stat. Methodol. 211–252. Brandt, S.A., 1992. Zero vs conventional tillage and their effects on crop yield and soil moisture. Can. J. Plant Sci. 72, 679–688. Braunack, M.V., McGarry, D., 2006. Traffic control and tillage strategies for harvesting and planting of sugarcane (Saccharum officinarum) in Australia. Soil Tillage Res. 89, 86–102. Camargo, A.P., Alfonsi, R.R., Chiarini, J.V., 1976. Zoneamento da aptidão climática para culturas comerciais em áreas de cerrado. SIMPOSIO SOBRE O CERRADO, 4., 1976 89–105. Chopart, J.L., Rodrigues, S.R., Azevedo, M.C., Medina, C.C., 2008. Estimating sugarcane root length density through root mapping and orientation modelling. Plant Soil 313, 101–112. Chopart, J.L., Azevedo, M.C., Le Mezo, L., Marion, D., 2010. Functional relationship between sugarcane root biomass and length for cropping system applications. Sugar Tech. 12, 317–321. de Maria, I.C., Castro, O.M., Souza Dias, H., 1999. Atributos físicos do solo e crescimento radicular de soja em latossolo roxo sob diferentes métodos de preparo do solo. R. Bras. Ci. Solo 23, 703–709. Fauconnier, R., Bassereau, D., 1970. La canne à sucre. Paris: Ed. Maisonneuve et Larose. (Collection techniques agricoles et productions tropicales). Galdos, M.V., Cerri, C.C., Cerri, C.E.P., Paustin, K., Van Antwerpen, R., 2009. Simulation of soil carbon dynamics under sugarcane with the CENTURY Model. Soil Sci. Soc. Am. J. 73, 802–811. Hammad, E.A., Dawelbeit, M.I., 2001. Effect of tillage and field condition on soil physical

118