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Effect of different mulching measures on nitrate nitrogen leaching in spring maize planting system in south of Loess Plateau
Agricultural Water Management 213 (2019) 654–658
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Agricultural Water Management journal homepage: www.elsevier.com/locate/agwat
Effect of different mulching measures on nitrate nitrogen leaching in spring maize planting system in south of Loess Plateau
T
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Qiang Donga,b,c, Tinghui Danga,b,c, , Shengli Guoa,b,c, Mingde Haoa,b,c a
Institue of Soil and Water Conservation, Northwest A & F University, Yangling, Shaanxi, 712100, PR China Institute of Soil and Water Conservation, Chinese Academy of Science & Ministry of Water Resources, Yangling, 712100, PR China c University of Chinese Academy of Sciences, Beijing, 100049, PR China b
A R T I C LE I N FO
A B S T R A C T
Keywords: Spring maize Straw-mulching Plastic film-mulching Nitrate nitrogen
Field experiment was conducted in the southern gully region of the Loess Plateau to study the effects of different mulching measures on spring maize yield and nitrate leaching in dryland under the traditional tillage conditions, so as to provide a scientific basis for spring maize planting and environmental protection in this area. The four treatments included non-mulching (CK), plastic film-mulching (PM1), plastic film-mulching in fallow (PM2) and straw-mulching (JM). After 13 years of continuous application, the yield of spring maize, the nitrogen uptake by plants and the nitrate nitrogen content at the harvest stage were measured. The results showed that the soil moisture content and water storage capacity of three kinds of soil mulching treatments were all higher than those of non-mulching ones. Soil water storage in the range of 0 ∼ 300 cm of JM, PM1 and PM2 increased by 11.8%, 10.6% and 8.8% respectively compared with CK. Compared with CK, the mulching treatments significantly increased the aboveground biomass and grain yield of spring maize. The yield enhancement effect of PM1 was the most significant, with a yield of 11,314.42 kg / ha and an increase of 26.72%. In addition to the JM treatment, the accumulation of soil nitrate nitrogen in the range of 0 ∼ 300 cm of PM1 and PM2 was less than that of CK, but the increase of nitrate nitrogen of 80.20% of JM treatment was in the range of 0 ∼100 cm. Therefore, in the rain-fed agriculture in the south of Loess Plateau, mulching cultivation can effectively increase the soil moisture content and water storage, improve crop growth. The yield enhancement effect of plastic mulching-film was the best. PM1, PM2 could significantly reduce the content and accumulation of nitrate nitrogen in soil profile, and the three mulching measures could slow the deep leaching of soil nitrate nitrogen to a certain extent.
1. Introduction
can reduce water vapor transfer from the soil (Li et al., 1999, 2013), and increase soil temperature by reducing heat exchange between the atmosphere and the ground (Wu et al., 2016). Studies have indicated that mulching is conducive to crop growth by improving the soil water content and soil temperature in dryland agriculture (Cook et al., 2006). Mulching also has the benefit of improving soil physical conditions, including the protection of topsoil stability (De Silva and Cook, 2003). These changes in the soil environment are good for crop root growth, and the stronger ability of roots, which results in increased absorption of soil water and nutrients (Clark et al., 2003). Nitrogen is essential for plant growth and viability, and highyielding crops such as maize (Zea mays L.) are frequently treated with large amounts of N fertilizer to reach optimal yields (Jia et al., 2014). However, a higher N fertilizer input usually leads to nitrate nitrogen residue in soil. Furthermore, nitrate nitrogen residue can leach down
In China, about 21.7% of the total area is located in the semi-arid region, where the annual precipitation is in the range of 250 ∼ 550 mm, and the crop water requirement is in the range of 300 ∼ 600 mm (Li, 2007). Annual precipitation shows large variations from year to year and uneven distribution within seasons. In general, around 60 ∼ 70% of rainfall is concentrated during the months of June ∼ September (Wang et al., 2012). Therefore, in dryland farming systems, water stress and nutrient deficiency are the two major constraints for primary production, leading to low and unstable crop yields (Li et al., 2009; Sietz et al., 2011). In the Loess Plateau, straw-mulching and plastic film-mulching are two common mulching practices that are widely used in crop production, particularly maize production (Lin et al., 2016). Many studies have confirmed that plastic film-mulching
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Corresponding author at: Institue of Soil and Water Conservation, Northwest A & F University, Yangling, Shaanxi, 712100, PR China. E-mail address: [email protected] (T. Dang).
https://doi.org/10.1016/j.agwat.2018.09.044 Received 10 April 2018; Received in revised form 21 September 2018; Accepted 22 September 2018 0378-3774/ © 2018 Elsevier B.V. All rights reserved.
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straw harvested in this plot was mulched evenly, and the straw was closed when the corn was sowed and placed between the lines. Each treatment was replicated three times in 35 m2 plots (7 m × 5 m) in a randomized complete block design. The test crop is a ripe spring corn a year, the selection of varieties is Pioneer 335. A planting pattern of alternating wide (60 cm) and narrow (35 cm) row spacing was used for each treatment. The spring corn was sown on April 23, 2016 and harvested on September 20. The test plastic film used for the 60 cm wide, 0.015 mm thick polyethylene film. Fertilizers (N 150 kg / ha and P2O5 75 kg / ha) were spread over the soil surface and incorporated into the 0 ∼ 20 cm soil layer using a rotary cultivator before sowing.
into the deep soil or loss by other ways. Due to limited irrigation and precipitation, nitrate leaching in cultivated lands of northwestern China has been underestimated or even ignored for many years (Yang et al., 2015). Therefore, efforts to harvest more rainfall to increase soil water storage and the optimization of N management to achieve higher crop yield have always been considered key steps in the sustainable development of dryland agriculture (He et al., 2016). However, the research on the transformation of soil nitrogen, especially the leaching of nitrate nitrogen, is rare under different mulching measures. Studies have shown that under the conditions of mulching and straw mulching, inorganic nitrogen can accumulate on the surface of the soil. Because of the change of soil temperature and moisture, it is bound to change the soil nitrogen and nitrate nitrogen leaching effects. Therefore, this paper aimed at different plastic film-mulching and straw-mulching, taking spring maize as the research object, discussed the nitrate leaching in soil under different mulching measures in the south of Loess Plateau.
2.3. Measurements 2.3.1. Grain yield Each plot harvested more than one-third of the ear, after air-drying, the collected samples were threshed and the grain was weighted. Subsamples (approximately 100 g) of the air-dried grain were dried to a constant weight in a fan oven at 75 °C to estimate the grain water content. The maize grain yield for each plot (adjusted to a moisture content of 14%), which was recorded on a plot basis, was converted to kilograms per hectare for statistical analysis (Liu et al., 2017).
2. Study area and methods 2.1. Study area The field experiment was conducted at the Changwu Experimental Station (35◦12′ N, 107◦40′ E and altitude 1206 m) on the Loess Plateau in Changwu county of Shaanxi Province, China. The climate is temperate semi-arid with a mean annual air temperature of 9.1 ± 2.3◦C, a mean monthly maximum temperature of 22◦C (July) and a mean monthly minimum temperature of −7◦C (January). The average annual sunshine duration is 2230 h with more than 171 frost-free days. The mean annual precipitation from 1990 to 2012 was 571 ± 74 mm, of which approximately 55% fell during the growing season between July and September. The rainfall during the experimental period was measured using an automatic weather station (Changwu experimental station meteorological observatory, WS-STD1, England) at the experimental site. According to the USDA textural classification system, the soil has a silty loam texture, which is derived from loess with a deep and even soil profile. The soil water content and wilting moisture in the 0 ∼ 10 m loess section were 21.16% ± 0.86% and 7.46% ± 0.65% (mass water content), respectively, and the soil bulk density was 1.23–1.44 g / cm3 (Wang et al., 2015). The precipitation and average temperature during the test in 2016 are shown in Fig. 1.
2.3.2. Soil moisture, nitrate nitrogen content determination After the harvest of the spring maize 2016, 0 ∼ 300 cm stratified soil samples were collected with a soil auger. Each plot selected 2 points, 0 ∼ 100 cm for every 10 cm layer, 100 cm below 20 cm for each layer, picked up to 300 cm. Two soil samples in the same plot were mixed with the same soil, into the plastic ziplock bag, refrigerated spare. In the sampling process, take a small amount of soil into the aluminum box at the same time, the samples were oven-dried at 105 °C for 24 h to a consistent weight to determine the gravimetric soil water content. In the laboratory, the soil was sieved (4 mm) to extract roots and stubble and then stored under cooled conditions (4 °C). The sieved field-moist soil samples were extracted with 1 mol L−1 KCl for 1 h at a 1:5 soil-to-extract ratio, and the NO3−-N concentration was determined using a continuous-flowing analyzer. 2.3.3. Plant sample collection and determination Each plot collected 3 representative plants in the middle, and then divided into stem, leaf, bract, rachis and grain, were weighed fresh weight, each take a mixed sample into the paper bag and set at 105 °C for 30 min, then 75 °C drying to constant weight, determination of its dry matter weight, crushed through 60 mesh sieve, H2SO4-H2O2 digestion and boiling, Kjeldahl determination of plant nitrogen.
2.2. Experimental design and treatments The experiment started in 2003 with a total of four treatments, the treatments were a control with non-mulching (CK), plastic filmmulching (PM1), plastic film-mulching in fallow (PM2) and strawmulching (JM). The CK treatment was not mulched during the entire growth stage；the PM1 treatment was mulched with plastic film before sowing; the PM2 treatment was plastic film-mulching in fallow, clean the mulch before sowing, without mulching during the growth period; The JM treatment was that when the corn was harvested, the whole
2.4. Data analysis (1) Water storage (W) in the profile was considered to be the total storage in all sampled layers in the plot and was calculated using the following formula: W = h×ρ×θ×10 h is soil depth (cm), ρ is soil bulk density (g / cm3) and θ is soil water content (%) in the corresponding soil layer. (2) Nitrogen harvest index (NHI%) = total grain nitrogen accumulation / total nitrogen accumulation in the plant (3) The amount of residual soil nitrate (RSN, kg N ha−1) in each soil layer can be calculated as: RSN = Ti × Di × Ci /10 Where Ti is the soil layer thickness, Di is the soil bulk density (g cm−3), Ci is the soil nitrate nitrogen concentration (mg N kg−1) of the corresponding layer, and 10 is the conversion coefficient (Dai et al., 2016). Statistical analysis of test data was performed using Microsoft Excel
Fig. 1. Precipitation and daily average temperature during the test in 2016. 655
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Table 1 Soil water storage under different mulching measures(mm). Soil layers (cm)
CK
PM1
PM2
JM
0 ∼ 60 60 ∼ 120 120 ∼ 200 0 ∼ 200 0 ∼ 300
151.24 147.15 191.33 489.72 713.73a
161.04 163.11 198.36 522.52 757.90a
163.18 169.85 209.35 542.38 789.37a
164.30 171.91 218.83 555.04 797.59b
Fig. 2. Soil moisture content at harvest stage under CK, PM1, PM2, JM treatments in 2016.
2013, Origin and SPSS 13.0 software. 3. Result 3.1. Effects of different mulching measures on soil moisture at harvest Stage Different mulching measures had different effects on the moisture content of soil profiles at the harvest stage of spring maize (Fig. 2). Compared with CK, the soil water content in the range of 0 ∼ 200 cm was higher than that in the CK treatment. There was no significant difference in the soil moisture content in the range of 200 ∼ 300 cm. The distribution of soil moisture in different treatments was similar in the whole profile: the soil moisture in the range of 0 ∼ 60 cm was consumed by spring maize and the soil water content showed a decreasing trend, the water content in the range of 60 ∼ 120 cm increased gradually, under 120 cm the soil water content began to decline; and soil water content in the range of 200 ∼ 300 cm did not change significantly. It was indicated that spring maize mainly used the soil moisture within the range of 0 ∼ 200 cm, so that the soil moisture in this area was consumed greatly. The water content of soil profile at the harvest stage was JM > PM2 > PM1 from top to bottom, which was related to the different movement of soil moisture under the three treatments. The surface of the PM1 was exposed during the fallow period, which increased the loss of soil water; the surface of the land was in the semi-mulching state during the growth period, and the rainfall in May to June in the test site was small and the plant had a large amount of water consumption, therefore, resulting in a large amount of water loss; however, in July and August, when the rainfall increased, the leaf area of spring maize plants increased, blocking most of the rainfall, so that the soil moisture of PM1 was not replenished. JM treatment and PM2 treatment resulted in less water loss due to increased surface mulching during fallow period and increased rainfall infiltration during early spring maize growth period. Therefore, the soil profile moisture content of PM1 treatment was lower than that of other mulching treatment. The water storage in the harvest period ranged from 713 to 797 mm in the range of 0 ∼ 300 cm and the amount of water storage in order of JM > PM2 > PM1 > CK (Table 1). The water storage capacity of JM, PM2 and PM1 treatments increased by 11.7%, 10.6% and 6.2% respectively as compared with CK treatment, indicated that JM treatment had the strongest effect on soil water storage. In addition, the water storage capacity of three kinds of soil mulching treatments during harvest increased from shallow to deep, while the storage capacity of 60 ∼ 120 cm in CK treatment was lower than the storage capacity of 0 ∼ 60 cm, and the CK storage capacity were lower than the mulching treatments. The above results showed that mulching the ground can effectively increase the water storage capacity of the soil during harvest
Fig. 3. Nitrate nitrogen content in soil profiles under different mulching measures.
stage, while non-mulching treatment will increase the loss of soil water and reduce the soil water storage capacity at harvest stage. Different letters in the same row indicated that the data difference was significant at the 0.05 level. 3.2. Profile distribution and accumulation of soil nitrate under different mulching measures Nitrate nitrogen data at the soil profile at harvest showed that the plastic film-mulching significantly reduced nitrate nitrogen content in the soil profile (Fig. 3). The content of NO3−-N in PM2 decreased in the whole profile. The content of NO3−-N in PM1 fluctuated in the whole profile, and the peak appeared at 140 cm (7.63 mg / kg). CK had two accumulation peaks in the whole profile. The first accumulation peak was at 60 cm, the nitrate content was 42.36 mg / kg. The second accumulation peak was at 180 cm with nitrate content of 15.27 mg / kg. Compared with CK treatment, JM treatment showed that the nitrate nitrogen content in the range of 0 ∼ 50 cm was much higher than that in CK treatment, with a cumulative peak at 40 cm (63.01 mg / kg). From below 50 cm, JM treatment nitrate nitrogen concentration has been declining and nitrate content below 120 cm below CK treatment. In the same experiment, the peak value of CK treatment increased from 30.9 mg / kg to 42.36 mg / kg compared with the nitrate nitrogen content at the harvest stage in 2007 (Yang, 2009), and a new cumulated peak was formed at 180 cm. In 2007 the peak value of JM treatment was 60 cm, the content of soil nitrate nitrogen was 30.9 mg / kg, and the same depth of nitrate nitrogen content was 31.95 mg / kg in 2016. The peak of PM1 treatment varied from 5.8 mg / kg at 60 cm to 140 cm at 7.63 mg / kg. According to the accumulations of nitrate nitrogen in soil profile in the range of 0 ∼ 300 cm during the harvest period in 2016 (Table 2), the accumulations of nitrate nitrogen in different treatments were JM > CK > PM1 > PM2 in descending order. Except for JM treatment, the other three treatments were significantly less than the CK accumulation, the cumulative amount of 100 ∼ 200 cm within the three mulching treatments were lower than the CK treatment, indicated that mulching cultivation on the surface can significantly reduce the 656
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Table 2 The accumulation of NO3−-N in soil profile under different mulching measures in 2016 and 2007(kg / ha). Treatment
CK
PM1
PM2
Soil layers (cm) 0∼100 cm 100∼200 cm 0∼200 cm 0∼300 cm
2016
2007
2016
2007
2016
2007
2016
2007
221.87 166.77 388.64 451.71a
158.67 148.83 307.50 328.24
57.52 83.18 140.7 180.76b
60.29 14.50 74.78 101.51
44.79 15.81 60.60 76.66
\ \ \ \
483.54 116.18 599.72 679.94c
171.13 91.00 262.13 290.37b
soil profile in the soil range of 100 ∼ 200 cm nitrate accumulation. Compared with the data from 2007 (Yang, 2009), the accumulation of nitrate nitrogen in soil profile (0 ∼ 300 cm) CK, PM1 and JM increased by 123.47 kg / ha, 79.25 kg / ha and 389.57 kg / ha, respectively. The increment of nitrate content in 80.20% of JM treatment was in the range of 0 ∼ 100 cm, indicated that straw-mulching could significantly increase the accumulation of nitrate in shallow soil. Based on the data of distribution of nitrate nitrogen in soil profiles at harvest stage (Fig. 3), it can be concluded that all the mulching measures can effectively reduce the leaching and accumulation of nitrate in soil. Different letters in the same row indicated that the data difference was significant at the 0.05 level.
4. Discussion The main form of nitrogen in rainfed farmland soil is nitrate nitrogen, and water is the carrier of nitrate nitrogen in soil. As for the influence of different mulching measures on soil water content and water storage capacity, different researchers carried out relevant experimental studies in different regions. Studies (Zhang et al., 2007; Zribi et al., 2015) had shown that mulching can increase soil water content and water storage capacity by reducing ineffective evaporation and raising the soil's deeper water to the crop-available layer than baresoil cultivation. Straw mulching also helps to reduce ineffective evaporation and improve soil moisture (Zhang et al., 2011; Wu et al., 2016). Zhang et al (2010) tested the planting and harvesting of maize under different plastic film mulching in arid highland of northern Weibei upland, the results showed that different types of plastic mulching had the same influence on soil water content. Compared with the non-mulching, the surface water content and soil water storage capacity increased significantly. Li et al (2016) studied the spring maize in Heyang, Shaanxi Province, the results showed that straw mulching provided greater water conservation. In our experiment, the average water content of 0 ∼ 300 cm soil layer in the period of harvest with plastic mulching, plastic film-mulching in fallow and straw-mulching increased by 6.24%, 10.6%, 11.76% compared with non-mulching treatment, respectively. In three kinds of mulching treatment, the straw-mulching had the best effect. The water storage capacity of 0 ∼ 300 cm increased by 11.8% compared with the non-mulching treatment. Mulching significantly increased the emergence rate of maize, increased the dry matter accumulation aboveground and promoted the growth and development of ear, improve corn production. Plastic film mulching was significantly increasing the maize yield in the Loess Plateau (Zhang et al., 2007, 2011; Wang et al., 2015). Different effects of straw mulching on spring maize yield have been reported. Some studies had shown that the low temperature effect due to straw mulching in early spring maize leads to a decrease in yield (Zhang et al., 2011; Wu et al., 2016). But Wang et al (2011) showed that straw mulching increased by 45.67% compared with no mulching and film mulching increased by 47.24%. In this experiment, plastic film mulching treatment increased by 23.72% of the yield compared with the control treatment. In addition to improving the soil moisture status and increasing the yield, the mulching measures also have a great impact on the leaching and transformation of soil nitrate nitrogen. The mulching prevented the direct vertical infiltration of precipitation from the surface of the soil, and most of the water can only infiltrate the trench to enhance the lateral movement of water, and then increase the upward movement of water on the plastic film ridge, reducing the nitrate nitrogen to the deep migration (Zhang et al., 2012). Moreover, studies have found that soil mulching significantly increased maize N uptake efficiency and utilization efficiency compared with the non-mulching treatment, and the grain yield and total N uptake increase may decrease the nitrate nitrogen residue in soil. In our study, the contents and accumulation of nitrate nitrogen in soil profiles with plastic film-mulching and plastic film-mulching in fallow were significantly reduced, the accumulations of nitrate nitrogen in the soil profiles of three kinds of mulching treatments in the range of 100 ∼ 200 cm were lower than those of the
3.3. Yield and N uptake of spring maize under different mulching measures Mulching significantly increased biomass and grain yield in spring maize compared to non-mulching (Table 3). After harvesting in 2016, the aboveground biomass of all treatments were PM1 > JM > PM2 > CK in descending order. Among them, the biomass of PM1 and CK was significantly different (P < 0.05), the biomass of which was increased by 28.05% compared with that of CK. The difference between JM and CK was not statistically significant, but the biomass of JM increased by 11.13% compared with CK treatment. The yield of PM1 was the most significant, with the yield of 11,314.42 kg / ha. Compared with CK, the yield of PM1 increased by 26.72%. The yields of JM and PM2 were not significantly different from those of CK, but the yield of both treatments were higher than that of CK by 9.2% and 5% respectively. The biomass and grain yield of PM1 were significantly higher than those of JM and PM2 (P < 0.05). Values followed by different letters in a column are significantly different among the treatments at the 5% level. The NHI indicates the efficiency with which the crop utilizes the acquired N for grain production. Compared with the control treatment, the plant nitrogen uptake and the grain nitrogen uptake except the PM2 were all greater than those of the CK treatment, indicated that the mulching cultivation of the spring maize increased the nitrogen uptake by the spring maize plants. Meanwhile, each mulching nitrogen index were higher than the control treatment, indicated a higher nitrogen content in the leaves and stems of the control treatment, more nitrogen is used for vegetative growth; and mulching treatment can make plants absorb nitrogen more transfer more to the grain for reproductive growth. Table 3 Aboveground biomass and yield of spring maize with different mulching measures. Treatment
Aboveground biomass(kg/ha)
Grain yield (kg/ha)
Plant nitrogen uptake (kg/ha)
Grain nitrogen uptake (kg/ha)
Nitrogen harvest index(%)
CK PM1 PM2 JM
16028.64a 20524.11b 17373.28a 17812.42a
8928.22a 11314.42b 9370.88a 9747.13a
164.32a 197.76b 161.12a 170.20a
101.44a 128.56a 104.80a 114.08a
61.73 65.00 65.04 64.03
JM
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non-mulching ones. In addition, the three mulching treatments effectively increased the nitrogen uptake and the nitrogen harvest index of spring maize, which is consistent with the previous studies. Zhang et al (2009) found that the residual nitrate nitrogen in soil was significantly increased when the nitrogen application rate was higher than 150 kg / ha, with or without straw-mulching, 0 ∼ 200 cm section obvious accumulation peak, straw-mulching soil residual nitrate accumulation peak than the non-mulching depth of about 40 cm. In our experiment, the nitrogen application rate was 150 kg / ha. The soil nitrate nitrogen content and accumulation in the range of 0 ∼ 50 cm with straw mulching were significantly higher than the non-mulching treatment, and the accumulation of nitrate nitrogen in the range of 0 ∼ 100 cm with straw mulching was significantly greater than the other treatments, while the accumulation of nitrate nitrogen in the range of 100 ∼ 200 cm in straw mulching treatment was less than that in non-mulching treatment. The results showed that straw-mulching could significantly increase nitrate nitrogen content in the soil surface but did not cause downward leaching. Some studies have shown that straw-mulching can significantly increase the nitrate nitrogen content of soil surface, promote the supply of nitrogen, reduce the residual nitrate nitrogen and reduce the leaching loss (Wang et al., 2014; He et al., 2016). This is mainly due to the continuous application of higher C / N ratio straw, which greatly increased the amount of bio-available carbon in the soil, provided sufficient energy for the activities of soil heterotrophic microorganisms and greatly stimulated the mineralization of soil nitrogen role (Mary et al., 1996; Recous et al., 1999). Therefore, in arid and semi-arid areas, maize mulching cultivation can effectively reduce soil nitrate nitrogen leaching and accumulation.
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5. Conclusion (1) In rainfed agriculture in the south of Loess Plateau, the mulching measures can effectively increase the soil water content and water storage capacity and improve the crop growth. (2) Plastic film-mulching is the best way to increase yield of corn, increased by 23.72% of the yield compared with the non-mulching. (3) Plastic film-mulching, plastic film-mulching in fallow can significantly reduce the content and accumulation of nitrate nitrogen in the soil profile, and the three mulching measures can slow the deep leaching of soil nitrate nitrogen to a certain extent. Acknowledgments This research was supported by National key R&D Program of China (2016YFD0800105). References Clark, L.J., Whalley, W.R., Barraclough, P.B., 2003. How do roots penetrate strong soil? Plant Soil 255, 93–104. Cook, H.F., Valdes, G.S.B., Lee, H.C., 2006. Mulch effects on rainfall interception, soil physical characteristics and temperature under Zea mays L. Soil Till. Res. 91, 227–235. Dai, J., Wang, Z.H., Li, M.H., He, G., Li, Q., Cao, H.B., Wang, S., Gao, Y.J., Hui, X.L., 2016. Winter wheat grain yield and summer nitrate leaching: long-term effects of nitrogen and phosphorus rates on the Loess Plateau of China. Field Crops Res. 196, 180–190. De Silva, S.H., Cook, H.F., 2003. Soil physical conditions and performance of cowpea following organic matter amelioration of sand. Commun. Soil Sci. Plant Anal. 34,
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Effect of different mulching measures on nitrate nitrogen leaching in spring maize planting system in south of Loess Plateau
T
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Qiang Donga,b,c, Tinghui Danga,b,c, , Shengli Guoa,b,c, Mingde Haoa,b,c a
Institue of Soil and Water Conservation, Northwest A & F University, Yangling, Shaanxi, 712100, PR China Institute of Soil and Water Conservation, Chinese Academy of Science & Ministry of Water Resources, Yangling, 712100, PR China c University of Chinese Academy of Sciences, Beijing, 100049, PR China b
A R T I C LE I N FO
A B S T R A C T
Keywords: Spring maize Straw-mulching Plastic film-mulching Nitrate nitrogen
Field experiment was conducted in the southern gully region of the Loess Plateau to study the effects of different mulching measures on spring maize yield and nitrate leaching in dryland under the traditional tillage conditions, so as to provide a scientific basis for spring maize planting and environmental protection in this area. The four treatments included non-mulching (CK), plastic film-mulching (PM1), plastic film-mulching in fallow (PM2) and straw-mulching (JM). After 13 years of continuous application, the yield of spring maize, the nitrogen uptake by plants and the nitrate nitrogen content at the harvest stage were measured. The results showed that the soil moisture content and water storage capacity of three kinds of soil mulching treatments were all higher than those of non-mulching ones. Soil water storage in the range of 0 ∼ 300 cm of JM, PM1 and PM2 increased by 11.8%, 10.6% and 8.8% respectively compared with CK. Compared with CK, the mulching treatments significantly increased the aboveground biomass and grain yield of spring maize. The yield enhancement effect of PM1 was the most significant, with a yield of 11,314.42 kg / ha and an increase of 26.72%. In addition to the JM treatment, the accumulation of soil nitrate nitrogen in the range of 0 ∼ 300 cm of PM1 and PM2 was less than that of CK, but the increase of nitrate nitrogen of 80.20% of JM treatment was in the range of 0 ∼100 cm. Therefore, in the rain-fed agriculture in the south of Loess Plateau, mulching cultivation can effectively increase the soil moisture content and water storage, improve crop growth. The yield enhancement effect of plastic mulching-film was the best. PM1, PM2 could significantly reduce the content and accumulation of nitrate nitrogen in soil profile, and the three mulching measures could slow the deep leaching of soil nitrate nitrogen to a certain extent.
1. Introduction
can reduce water vapor transfer from the soil (Li et al., 1999, 2013), and increase soil temperature by reducing heat exchange between the atmosphere and the ground (Wu et al., 2016). Studies have indicated that mulching is conducive to crop growth by improving the soil water content and soil temperature in dryland agriculture (Cook et al., 2006). Mulching also has the benefit of improving soil physical conditions, including the protection of topsoil stability (De Silva and Cook, 2003). These changes in the soil environment are good for crop root growth, and the stronger ability of roots, which results in increased absorption of soil water and nutrients (Clark et al., 2003). Nitrogen is essential for plant growth and viability, and highyielding crops such as maize (Zea mays L.) are frequently treated with large amounts of N fertilizer to reach optimal yields (Jia et al., 2014). However, a higher N fertilizer input usually leads to nitrate nitrogen residue in soil. Furthermore, nitrate nitrogen residue can leach down
In China, about 21.7% of the total area is located in the semi-arid region, where the annual precipitation is in the range of 250 ∼ 550 mm, and the crop water requirement is in the range of 300 ∼ 600 mm (Li, 2007). Annual precipitation shows large variations from year to year and uneven distribution within seasons. In general, around 60 ∼ 70% of rainfall is concentrated during the months of June ∼ September (Wang et al., 2012). Therefore, in dryland farming systems, water stress and nutrient deficiency are the two major constraints for primary production, leading to low and unstable crop yields (Li et al., 2009; Sietz et al., 2011). In the Loess Plateau, straw-mulching and plastic film-mulching are two common mulching practices that are widely used in crop production, particularly maize production (Lin et al., 2016). Many studies have confirmed that plastic film-mulching
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Corresponding author at: Institue of Soil and Water Conservation, Northwest A & F University, Yangling, Shaanxi, 712100, PR China. E-mail address: [email protected] (T. Dang).
https://doi.org/10.1016/j.agwat.2018.09.044 Received 10 April 2018; Received in revised form 21 September 2018; Accepted 22 September 2018 0378-3774/ © 2018 Elsevier B.V. All rights reserved.
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straw harvested in this plot was mulched evenly, and the straw was closed when the corn was sowed and placed between the lines. Each treatment was replicated three times in 35 m2 plots (7 m × 5 m) in a randomized complete block design. The test crop is a ripe spring corn a year, the selection of varieties is Pioneer 335. A planting pattern of alternating wide (60 cm) and narrow (35 cm) row spacing was used for each treatment. The spring corn was sown on April 23, 2016 and harvested on September 20. The test plastic film used for the 60 cm wide, 0.015 mm thick polyethylene film. Fertilizers (N 150 kg / ha and P2O5 75 kg / ha) were spread over the soil surface and incorporated into the 0 ∼ 20 cm soil layer using a rotary cultivator before sowing.
into the deep soil or loss by other ways. Due to limited irrigation and precipitation, nitrate leaching in cultivated lands of northwestern China has been underestimated or even ignored for many years (Yang et al., 2015). Therefore, efforts to harvest more rainfall to increase soil water storage and the optimization of N management to achieve higher crop yield have always been considered key steps in the sustainable development of dryland agriculture (He et al., 2016). However, the research on the transformation of soil nitrogen, especially the leaching of nitrate nitrogen, is rare under different mulching measures. Studies have shown that under the conditions of mulching and straw mulching, inorganic nitrogen can accumulate on the surface of the soil. Because of the change of soil temperature and moisture, it is bound to change the soil nitrogen and nitrate nitrogen leaching effects. Therefore, this paper aimed at different plastic film-mulching and straw-mulching, taking spring maize as the research object, discussed the nitrate leaching in soil under different mulching measures in the south of Loess Plateau.
2.3. Measurements 2.3.1. Grain yield Each plot harvested more than one-third of the ear, after air-drying, the collected samples were threshed and the grain was weighted. Subsamples (approximately 100 g) of the air-dried grain were dried to a constant weight in a fan oven at 75 °C to estimate the grain water content. The maize grain yield for each plot (adjusted to a moisture content of 14%), which was recorded on a plot basis, was converted to kilograms per hectare for statistical analysis (Liu et al., 2017).
2. Study area and methods 2.1. Study area The field experiment was conducted at the Changwu Experimental Station (35◦12′ N, 107◦40′ E and altitude 1206 m) on the Loess Plateau in Changwu county of Shaanxi Province, China. The climate is temperate semi-arid with a mean annual air temperature of 9.1 ± 2.3◦C, a mean monthly maximum temperature of 22◦C (July) and a mean monthly minimum temperature of −7◦C (January). The average annual sunshine duration is 2230 h with more than 171 frost-free days. The mean annual precipitation from 1990 to 2012 was 571 ± 74 mm, of which approximately 55% fell during the growing season between July and September. The rainfall during the experimental period was measured using an automatic weather station (Changwu experimental station meteorological observatory, WS-STD1, England) at the experimental site. According to the USDA textural classification system, the soil has a silty loam texture, which is derived from loess with a deep and even soil profile. The soil water content and wilting moisture in the 0 ∼ 10 m loess section were 21.16% ± 0.86% and 7.46% ± 0.65% (mass water content), respectively, and the soil bulk density was 1.23–1.44 g / cm3 (Wang et al., 2015). The precipitation and average temperature during the test in 2016 are shown in Fig. 1.
2.3.2. Soil moisture, nitrate nitrogen content determination After the harvest of the spring maize 2016, 0 ∼ 300 cm stratified soil samples were collected with a soil auger. Each plot selected 2 points, 0 ∼ 100 cm for every 10 cm layer, 100 cm below 20 cm for each layer, picked up to 300 cm. Two soil samples in the same plot were mixed with the same soil, into the plastic ziplock bag, refrigerated spare. In the sampling process, take a small amount of soil into the aluminum box at the same time, the samples were oven-dried at 105 °C for 24 h to a consistent weight to determine the gravimetric soil water content. In the laboratory, the soil was sieved (4 mm) to extract roots and stubble and then stored under cooled conditions (4 °C). The sieved field-moist soil samples were extracted with 1 mol L−1 KCl for 1 h at a 1:5 soil-to-extract ratio, and the NO3−-N concentration was determined using a continuous-flowing analyzer. 2.3.3. Plant sample collection and determination Each plot collected 3 representative plants in the middle, and then divided into stem, leaf, bract, rachis and grain, were weighed fresh weight, each take a mixed sample into the paper bag and set at 105 °C for 30 min, then 75 °C drying to constant weight, determination of its dry matter weight, crushed through 60 mesh sieve, H2SO4-H2O2 digestion and boiling, Kjeldahl determination of plant nitrogen.
2.2. Experimental design and treatments The experiment started in 2003 with a total of four treatments, the treatments were a control with non-mulching (CK), plastic filmmulching (PM1), plastic film-mulching in fallow (PM2) and strawmulching (JM). The CK treatment was not mulched during the entire growth stage；the PM1 treatment was mulched with plastic film before sowing; the PM2 treatment was plastic film-mulching in fallow, clean the mulch before sowing, without mulching during the growth period; The JM treatment was that when the corn was harvested, the whole
2.4. Data analysis (1) Water storage (W) in the profile was considered to be the total storage in all sampled layers in the plot and was calculated using the following formula: W = h×ρ×θ×10 h is soil depth (cm), ρ is soil bulk density (g / cm3) and θ is soil water content (%) in the corresponding soil layer. (2) Nitrogen harvest index (NHI%) = total grain nitrogen accumulation / total nitrogen accumulation in the plant (3) The amount of residual soil nitrate (RSN, kg N ha−1) in each soil layer can be calculated as: RSN = Ti × Di × Ci /10 Where Ti is the soil layer thickness, Di is the soil bulk density (g cm−3), Ci is the soil nitrate nitrogen concentration (mg N kg−1) of the corresponding layer, and 10 is the conversion coefficient (Dai et al., 2016). Statistical analysis of test data was performed using Microsoft Excel
Fig. 1. Precipitation and daily average temperature during the test in 2016. 655
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Table 1 Soil water storage under different mulching measures(mm). Soil layers (cm)
CK
PM1
PM2
JM
0 ∼ 60 60 ∼ 120 120 ∼ 200 0 ∼ 200 0 ∼ 300
151.24 147.15 191.33 489.72 713.73a
161.04 163.11 198.36 522.52 757.90a
163.18 169.85 209.35 542.38 789.37a
164.30 171.91 218.83 555.04 797.59b
Fig. 2. Soil moisture content at harvest stage under CK, PM1, PM2, JM treatments in 2016.
2013, Origin and SPSS 13.0 software. 3. Result 3.1. Effects of different mulching measures on soil moisture at harvest Stage Different mulching measures had different effects on the moisture content of soil profiles at the harvest stage of spring maize (Fig. 2). Compared with CK, the soil water content in the range of 0 ∼ 200 cm was higher than that in the CK treatment. There was no significant difference in the soil moisture content in the range of 200 ∼ 300 cm. The distribution of soil moisture in different treatments was similar in the whole profile: the soil moisture in the range of 0 ∼ 60 cm was consumed by spring maize and the soil water content showed a decreasing trend, the water content in the range of 60 ∼ 120 cm increased gradually, under 120 cm the soil water content began to decline; and soil water content in the range of 200 ∼ 300 cm did not change significantly. It was indicated that spring maize mainly used the soil moisture within the range of 0 ∼ 200 cm, so that the soil moisture in this area was consumed greatly. The water content of soil profile at the harvest stage was JM > PM2 > PM1 from top to bottom, which was related to the different movement of soil moisture under the three treatments. The surface of the PM1 was exposed during the fallow period, which increased the loss of soil water; the surface of the land was in the semi-mulching state during the growth period, and the rainfall in May to June in the test site was small and the plant had a large amount of water consumption, therefore, resulting in a large amount of water loss; however, in July and August, when the rainfall increased, the leaf area of spring maize plants increased, blocking most of the rainfall, so that the soil moisture of PM1 was not replenished. JM treatment and PM2 treatment resulted in less water loss due to increased surface mulching during fallow period and increased rainfall infiltration during early spring maize growth period. Therefore, the soil profile moisture content of PM1 treatment was lower than that of other mulching treatment. The water storage in the harvest period ranged from 713 to 797 mm in the range of 0 ∼ 300 cm and the amount of water storage in order of JM > PM2 > PM1 > CK (Table 1). The water storage capacity of JM, PM2 and PM1 treatments increased by 11.7%, 10.6% and 6.2% respectively as compared with CK treatment, indicated that JM treatment had the strongest effect on soil water storage. In addition, the water storage capacity of three kinds of soil mulching treatments during harvest increased from shallow to deep, while the storage capacity of 60 ∼ 120 cm in CK treatment was lower than the storage capacity of 0 ∼ 60 cm, and the CK storage capacity were lower than the mulching treatments. The above results showed that mulching the ground can effectively increase the water storage capacity of the soil during harvest
Fig. 3. Nitrate nitrogen content in soil profiles under different mulching measures.
stage, while non-mulching treatment will increase the loss of soil water and reduce the soil water storage capacity at harvest stage. Different letters in the same row indicated that the data difference was significant at the 0.05 level. 3.2. Profile distribution and accumulation of soil nitrate under different mulching measures Nitrate nitrogen data at the soil profile at harvest showed that the plastic film-mulching significantly reduced nitrate nitrogen content in the soil profile (Fig. 3). The content of NO3−-N in PM2 decreased in the whole profile. The content of NO3−-N in PM1 fluctuated in the whole profile, and the peak appeared at 140 cm (7.63 mg / kg). CK had two accumulation peaks in the whole profile. The first accumulation peak was at 60 cm, the nitrate content was 42.36 mg / kg. The second accumulation peak was at 180 cm with nitrate content of 15.27 mg / kg. Compared with CK treatment, JM treatment showed that the nitrate nitrogen content in the range of 0 ∼ 50 cm was much higher than that in CK treatment, with a cumulative peak at 40 cm (63.01 mg / kg). From below 50 cm, JM treatment nitrate nitrogen concentration has been declining and nitrate content below 120 cm below CK treatment. In the same experiment, the peak value of CK treatment increased from 30.9 mg / kg to 42.36 mg / kg compared with the nitrate nitrogen content at the harvest stage in 2007 (Yang, 2009), and a new cumulated peak was formed at 180 cm. In 2007 the peak value of JM treatment was 60 cm, the content of soil nitrate nitrogen was 30.9 mg / kg, and the same depth of nitrate nitrogen content was 31.95 mg / kg in 2016. The peak of PM1 treatment varied from 5.8 mg / kg at 60 cm to 140 cm at 7.63 mg / kg. According to the accumulations of nitrate nitrogen in soil profile in the range of 0 ∼ 300 cm during the harvest period in 2016 (Table 2), the accumulations of nitrate nitrogen in different treatments were JM > CK > PM1 > PM2 in descending order. Except for JM treatment, the other three treatments were significantly less than the CK accumulation, the cumulative amount of 100 ∼ 200 cm within the three mulching treatments were lower than the CK treatment, indicated that mulching cultivation on the surface can significantly reduce the 656
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Table 2 The accumulation of NO3−-N in soil profile under different mulching measures in 2016 and 2007(kg / ha). Treatment
CK
PM1
PM2
Soil layers (cm) 0∼100 cm 100∼200 cm 0∼200 cm 0∼300 cm
2016
2007
2016
2007
2016
2007
2016
2007
221.87 166.77 388.64 451.71a
158.67 148.83 307.50 328.24
57.52 83.18 140.7 180.76b
60.29 14.50 74.78 101.51
44.79 15.81 60.60 76.66
\ \ \ \
483.54 116.18 599.72 679.94c
171.13 91.00 262.13 290.37b
soil profile in the soil range of 100 ∼ 200 cm nitrate accumulation. Compared with the data from 2007 (Yang, 2009), the accumulation of nitrate nitrogen in soil profile (0 ∼ 300 cm) CK, PM1 and JM increased by 123.47 kg / ha, 79.25 kg / ha and 389.57 kg / ha, respectively. The increment of nitrate content in 80.20% of JM treatment was in the range of 0 ∼ 100 cm, indicated that straw-mulching could significantly increase the accumulation of nitrate in shallow soil. Based on the data of distribution of nitrate nitrogen in soil profiles at harvest stage (Fig. 3), it can be concluded that all the mulching measures can effectively reduce the leaching and accumulation of nitrate in soil. Different letters in the same row indicated that the data difference was significant at the 0.05 level.
4. Discussion The main form of nitrogen in rainfed farmland soil is nitrate nitrogen, and water is the carrier of nitrate nitrogen in soil. As for the influence of different mulching measures on soil water content and water storage capacity, different researchers carried out relevant experimental studies in different regions. Studies (Zhang et al., 2007; Zribi et al., 2015) had shown that mulching can increase soil water content and water storage capacity by reducing ineffective evaporation and raising the soil's deeper water to the crop-available layer than baresoil cultivation. Straw mulching also helps to reduce ineffective evaporation and improve soil moisture (Zhang et al., 2011; Wu et al., 2016). Zhang et al (2010) tested the planting and harvesting of maize under different plastic film mulching in arid highland of northern Weibei upland, the results showed that different types of plastic mulching had the same influence on soil water content. Compared with the non-mulching, the surface water content and soil water storage capacity increased significantly. Li et al (2016) studied the spring maize in Heyang, Shaanxi Province, the results showed that straw mulching provided greater water conservation. In our experiment, the average water content of 0 ∼ 300 cm soil layer in the period of harvest with plastic mulching, plastic film-mulching in fallow and straw-mulching increased by 6.24%, 10.6%, 11.76% compared with non-mulching treatment, respectively. In three kinds of mulching treatment, the straw-mulching had the best effect. The water storage capacity of 0 ∼ 300 cm increased by 11.8% compared with the non-mulching treatment. Mulching significantly increased the emergence rate of maize, increased the dry matter accumulation aboveground and promoted the growth and development of ear, improve corn production. Plastic film mulching was significantly increasing the maize yield in the Loess Plateau (Zhang et al., 2007, 2011; Wang et al., 2015). Different effects of straw mulching on spring maize yield have been reported. Some studies had shown that the low temperature effect due to straw mulching in early spring maize leads to a decrease in yield (Zhang et al., 2011; Wu et al., 2016). But Wang et al (2011) showed that straw mulching increased by 45.67% compared with no mulching and film mulching increased by 47.24%. In this experiment, plastic film mulching treatment increased by 23.72% of the yield compared with the control treatment. In addition to improving the soil moisture status and increasing the yield, the mulching measures also have a great impact on the leaching and transformation of soil nitrate nitrogen. The mulching prevented the direct vertical infiltration of precipitation from the surface of the soil, and most of the water can only infiltrate the trench to enhance the lateral movement of water, and then increase the upward movement of water on the plastic film ridge, reducing the nitrate nitrogen to the deep migration (Zhang et al., 2012). Moreover, studies have found that soil mulching significantly increased maize N uptake efficiency and utilization efficiency compared with the non-mulching treatment, and the grain yield and total N uptake increase may decrease the nitrate nitrogen residue in soil. In our study, the contents and accumulation of nitrate nitrogen in soil profiles with plastic film-mulching and plastic film-mulching in fallow were significantly reduced, the accumulations of nitrate nitrogen in the soil profiles of three kinds of mulching treatments in the range of 100 ∼ 200 cm were lower than those of the
3.3. Yield and N uptake of spring maize under different mulching measures Mulching significantly increased biomass and grain yield in spring maize compared to non-mulching (Table 3). After harvesting in 2016, the aboveground biomass of all treatments were PM1 > JM > PM2 > CK in descending order. Among them, the biomass of PM1 and CK was significantly different (P < 0.05), the biomass of which was increased by 28.05% compared with that of CK. The difference between JM and CK was not statistically significant, but the biomass of JM increased by 11.13% compared with CK treatment. The yield of PM1 was the most significant, with the yield of 11,314.42 kg / ha. Compared with CK, the yield of PM1 increased by 26.72%. The yields of JM and PM2 were not significantly different from those of CK, but the yield of both treatments were higher than that of CK by 9.2% and 5% respectively. The biomass and grain yield of PM1 were significantly higher than those of JM and PM2 (P < 0.05). Values followed by different letters in a column are significantly different among the treatments at the 5% level. The NHI indicates the efficiency with which the crop utilizes the acquired N for grain production. Compared with the control treatment, the plant nitrogen uptake and the grain nitrogen uptake except the PM2 were all greater than those of the CK treatment, indicated that the mulching cultivation of the spring maize increased the nitrogen uptake by the spring maize plants. Meanwhile, each mulching nitrogen index were higher than the control treatment, indicated a higher nitrogen content in the leaves and stems of the control treatment, more nitrogen is used for vegetative growth; and mulching treatment can make plants absorb nitrogen more transfer more to the grain for reproductive growth. Table 3 Aboveground biomass and yield of spring maize with different mulching measures. Treatment
Aboveground biomass(kg/ha)
Grain yield (kg/ha)
Plant nitrogen uptake (kg/ha)
Grain nitrogen uptake (kg/ha)
Nitrogen harvest index(%)
CK PM1 PM2 JM
16028.64a 20524.11b 17373.28a 17812.42a
8928.22a 11314.42b 9370.88a 9747.13a
164.32a 197.76b 161.12a 170.20a
101.44a 128.56a 104.80a 114.08a
61.73 65.00 65.04 64.03
JM
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non-mulching ones. In addition, the three mulching treatments effectively increased the nitrogen uptake and the nitrogen harvest index of spring maize, which is consistent with the previous studies. Zhang et al (2009) found that the residual nitrate nitrogen in soil was significantly increased when the nitrogen application rate was higher than 150 kg / ha, with or without straw-mulching, 0 ∼ 200 cm section obvious accumulation peak, straw-mulching soil residual nitrate accumulation peak than the non-mulching depth of about 40 cm. In our experiment, the nitrogen application rate was 150 kg / ha. The soil nitrate nitrogen content and accumulation in the range of 0 ∼ 50 cm with straw mulching were significantly higher than the non-mulching treatment, and the accumulation of nitrate nitrogen in the range of 0 ∼ 100 cm with straw mulching was significantly greater than the other treatments, while the accumulation of nitrate nitrogen in the range of 100 ∼ 200 cm in straw mulching treatment was less than that in non-mulching treatment. The results showed that straw-mulching could significantly increase nitrate nitrogen content in the soil surface but did not cause downward leaching. Some studies have shown that straw-mulching can significantly increase the nitrate nitrogen content of soil surface, promote the supply of nitrogen, reduce the residual nitrate nitrogen and reduce the leaching loss (Wang et al., 2014; He et al., 2016). This is mainly due to the continuous application of higher C / N ratio straw, which greatly increased the amount of bio-available carbon in the soil, provided sufficient energy for the activities of soil heterotrophic microorganisms and greatly stimulated the mineralization of soil nitrogen role (Mary et al., 1996; Recous et al., 1999). Therefore, in arid and semi-arid areas, maize mulching cultivation can effectively reduce soil nitrate nitrogen leaching and accumulation.
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5. Conclusion (1) In rainfed agriculture in the south of Loess Plateau, the mulching measures can effectively increase the soil water content and water storage capacity and improve the crop growth. (2) Plastic film-mulching is the best way to increase yield of corn, increased by 23.72% of the yield compared with the non-mulching. (3) Plastic film-mulching, plastic film-mulching in fallow can significantly reduce the content and accumulation of nitrate nitrogen in the soil profile, and the three mulching measures can slow the deep leaching of soil nitrate nitrogen to a certain extent. Acknowledgments This research was supported by National key R&D Program of China (2016YFD0800105). References Clark, L.J., Whalley, W.R., Barraclough, P.B., 2003. How do roots penetrate strong soil? Plant Soil 255, 93–104. Cook, H.F., Valdes, G.S.B., Lee, H.C., 2006. Mulch effects on rainfall interception, soil physical characteristics and temperature under Zea mays L. Soil Till. Res. 91, 227–235. Dai, J., Wang, Z.H., Li, M.H., He, G., Li, Q., Cao, H.B., Wang, S., Gao, Y.J., Hui, X.L., 2016. Winter wheat grain yield and summer nitrate leaching: long-term effects of nitrogen and phosphorus rates on the Loess Plateau of China. Field Crops Res. 196, 180–190. De Silva, S.H., Cook, H.F., 2003. Soil physical conditions and performance of cowpea following organic matter amelioration of sand. Commun. Soil Sci. Plant Anal. 34,
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