Modelling water, carbon and nitrogen dynamics in soil covered with decomposing mulch

A decomposing mulch of residues on the soil affects strongly the water, carbon and nitrogen cycling in the soil. The mulch generates complex and interacting effects that remain difficult to quantify and model. An original mulch module was developed and implemented in the PASTIS model to account for the main biological and physical effects of decomposing mulch. In the extended model, PASTIS_mulch, the formalism splits the mulch into a decomposable layer in contact with the soil and an overlying not decomposable layer that ‘feeds’ the former. The model was calibrated on laboratory data derived from mulched soil columns experiments. Two types of residues were tested: rape residues made of large elemental particles (length, 10 mm; width, 3–10 mm; thickness, 0.1–8 mm) with a C:N ratio of 29, and rye residues consisting of smaller particles (length, 10 mm; width, 2 mm; thickness, 0.1 mm) with a smaller C:N ratio of 16. Calibration showed that mulch parameters were dependent on the type of residue. The model run with calibrated parameters provided good simulations of the water, carbon and nitrogen dynamics, with global efficiencies greater than 0.8. The sensitivity analysis carried out on seven key parameters showed that the total mulch dry mass and the proportion of this dry mass in contact with the soil are decisive parameters. PASTIS_mulch highlighted that mulch decomposition was not a continuous process but occurred in the form of successive pulses that correspond to favourable hydric conditions.     

Impact of cattle slurry acidification on carbon and nitrogen dynamics during storage and after soil incorporation

Acidification of animal slurry is recommended in order to reduce NH₃ emissions, but relatively little is known about the effect of such treatment on C and N dynamics during acidification, storage, and after soil application. A laboratory study was performed, and the CO₂ emissions from a high–dry matter slurry (HDM), a low–dry matter slurry (LDM), and the same respective acidified slurries (AHDM and ALDM) were followed during a storage period and after soil incorporation. The N‐mineralization and nitrification processes, as well as microbial‐biomass activity were also estimated in soil receiving both the acidified and nonacidified materials. We observed a strong CO₂ emission during the acidification process, and acidification led to a small increase in CO₂ emissions (≈ 11%) during storage of AHDM relative to HDM. No effect of LDM acidification on CO₂ emissions during storage was observed. About 30% of C released during storage of AHDM was inorganic C, and for ALDM the C release was exclusively inorganic. Soil application of AHDM and ALDM led to a decrease in soil respiration, nitrification, and microbial‐biomass‐C values, relative to soil application of HDM and LDM, respectively. Furthermore, it was shown that this effect was more pronounced in ALDM‐ than AHDM‐treated soil. Considering both steps (storage and soil application), acidification led to a significant decrease of C losses and lower C losses were observed from LDM slurries than from HDM slurries.     

Yields of wheat and soil carbon and nitrogen contents following long-term incorporation of barley straw and ryegrass catch crops

Abstract. Three successive crops of winter wheat were grown on a sandy loam to test the residual effect of long‐term annual incorporation of spring barley straw at rates of 0, 4, 8 and 12 t ha^?1, and ryegrass catch crops with or without additions of pig slurry. Soil receiving 4, 8 and 12 t ha^?1 of straw annually for 18 years contained 12, 21 and 30% more carbon (C), respectively, than soil with straw removal, and soil C and nitrogen (N) contents increased linearly with straw rate. The soil retained 14% of the straw C and 37% of the straw N. Ryegrass catch‐cropping for 10 years also increased soil C and N concentrations, whereas the effect of pig slurry was insignificant. Grain yield in the first wheat crop showed an average dry matter (DM) increase of 0.7 t ha^?1 after treatment with 8 and 12 t straw ha^?1. In the two subsequent wheat crops, grain yield increased by 0.2–0.3 t DM ha^?1 after 8 and 12 t straw ha^?1. No grain yield increases were found after 4 t straw ha^?1 in any of the three years. Previous ryegrass catch crops increased yields of wheat grain, but effects in the third wheat crop were significant only where ryegrass had been combined with pig slurry. Straw incorporation increased the N offtake in the first wheat crop. In the second crop, only 8 and 12 t straw ha^?1 improved wheat N offtake, while the N offtake in the third wheat crop was unaffected. Ryegrass catch crops increased N offtake in the first and second wheat crop. Again, a positive effect in the third crop was seen only when ryegrass was combined with slurry. Long‐term, annual incorporation of straw and ryegrass catch crops provided a clear and relatively persistent increase in soil organic matter levels, whereas the positive effects on the yield of subsequent wheat crops were modest and transient.     

长期秸秆还田显著降低褐土底层有机碳储量

[目的]秸秆还田作为一种有效的培肥方式,对土壤固碳效果显著,但对于深层土壤有机碳的影响还存在不确定性.分析不同秸秆还田方式下褐土剖面土壤有机碳(SOC)储量变化,为褐土区秸秆还田措施优化和固碳减排等提供科学依据.[方法]长期秸秆还田试验开始于1992年,采用裂区设计,主区为化肥春季和秋季施用,副区为4个秸秆还田处理:秸...     

Soil moisture, carbon and nitrogen dynamics following incorporation and surface application of labelled crop residues in soil columns

One way to increase the amount of carbon sequestered in agricultural land is to convert conventional tillage into no‐tillage systems. This greatly affects the location of crop residues in soil. To investigate the impact of the location of residues on soil physical and biological properties and how the interactions between those properties influence the fate of carbon and nitrogen in soil, we did a laboratory experiment with repacked soil in columns. Doubly labelled ¹³C¹⁵N oilseed rape residues were incorporated in the 0–10 cm layer or left on the soil surface. The columns were incubated for 9 weeks at 20°C and were submitted to three cycles of drying and wetting, each of them induced by a rain simulator. The location of the residues affected the water dynamics and the distribution of C and N in the soil, which in turn influenced microbial activity and the decomposition rate of the added residues. After 9 weeks of’incubation, 18.4 ± 1.5% of the surface applied residue‐C and 54.7 ± 1.3% of the incorporated residue‐C was mineralized. We observed a nitrate accumulation of 10.7 mg N kg^?1 with residues at the soil surface, 3.6 mg N kg^?1 with incorporated residues and 6.3 mg N kg^?1 without addition of fresh organic matter, which entailed net N mineralization in soil under mulch and immobilization of N with residue incorporation compared with the control soil. We concluded that application of oilseed rape residues at the soil surface increased the storage of fresh organic C in soil in the short term, compared with the incorporation treatment, but increased the risk of nitrate leaching.     

秸秆生物炭配施氮肥对潮土土壤碳氮含量及作物产量的影响

【目的】探讨玉米秸秆生物炭配施氮肥对华北潮土区土壤理化特性和作物产量的影响,阐明土壤和植株对生物炭和氮肥施用的响应,旨在为该区域秸秆资源高效利用、培肥土壤及作物增产提供科学依据。【方法】以华北冬小麦–夏玉米轮作区为研究对象,研究玉米秸秆生物炭 (缺氧条件下 450℃ 热裂解 1 小时获得) 配施氮肥对土壤养分含量、微生物量以及作物产量的影响。试验采用裂区设计,以秸秆生物炭施用量为主区,施氮量为副区。秸秆生物炭用量设 0、7.5 和 22.5 t/hm2 3 个水平 (以 BC₀、BC_7.5、BC_22.5 表示);氮肥用量设 0、150、225 和 300 kg/hm2 4 个水平 (以 N₀、N₁₅₀、N₂₂₅、N₃₀₀ 表示)。小麦在 2014 年 10 月 9 日播种,次年 6 月 8 日收获;玉米在 2015 年 6 月 10 日播种,当年 9 月 28 日收获。在作物成熟期进行产量测定,并采集 0—20 cm 土壤样品以及采用常规方法进行土壤有机碳 (SOC)、全氮 (TN)、可溶性有机碳 (DOC)、铵态氮 (NH₄+-N)、硝态氮 (NO₃–-N)、土壤微生物量碳 (MBC) 和微生物量氮 (MBN) 的测定。【结果】生物炭对土壤养分含量、微生物量碳氮及作物产量有极显著影响。生物炭用量增加,土壤 SOC、TN、DOC、NO₃–-N 含量以及土壤 SOC/TN 比值均显著增加,较 BC₀ 最大增加幅度分别为 165.0%、74.1%、39.1%、75.1% 和 44.0%。MBC、MBN 含量和作物产量均以 BC_7.5 处理达最大值,较 BC₀ 最大增加幅度分别为 49.2%、57.6% 和 46.1%,BC_22.5 较 BC_7.5 处理平均降低 12.1%、7.3% 和 9.7%;施用生物炭降低 NH₄+-N 含量,BC_7.5 和 BC_22.5 处理较 BC₀ 分别下降 18.4% 和 23.7%。随着氮肥施用量的增加,SOC、DOC、NH₄+-N、MBC、MBN 含量均先增后减,在施氮水平为 150 kg/hm2 时,其含量均达最大值,较 N₀ 最大增加幅度分别为 29.7%、22.9%、44.8%、79.4% 和 115.3%。所有施氮的处理作物产量较 N₀ 均显著增加,而三个施氮处理间其产量差异不显著 (P>0.05)。【结论】在维持作物产量不降低的情况下,短期内 N₁₅₀BC_7.5 处理对提升土壤肥力的效果最佳,是较为理想的施肥方式,但其有效机制及长期效果还需进一步试验研究。     

长期稻秆还田对土壤微生物量及C、N动力学的影响

A study was performed on the long-term effect of straw incorporation on soil microbial biomass C contents, C and N dynamics in both Rothamsted and Woburn soils. The results showed that for both soils, the microbial biomass C contents were significantly different among all the treatments, and followed the sequence in treatments of straw chopped and incorporated into 10 cm (CI10) > straw burnt and incorporated into 10 cm (BI10) > straw chopped and incorporated into 20 cm (CI20) > straw burnt and incorporated into 20 cm (BI20). Laboratory incubation of soils showed that the cumulative CO₂ evolution was closely related to the soil microbial biomass C content. Carbon dioxide evolution rates (CO₂-C, μg (g•d)^-1) decreased rapidly in the first two weeks' incubation, then decreased more slowly. The initial K₂SO₄-extractable NH₄-N and NO₃-N contents were low and similar in all the treatments, and all increased gradually with the incubation time. However, net N immobilization was observed in chopped treatments for Rothamsted soils during the first 4 weeks. Nevertheless, more N mineralization occurred in Treatment CI10 than any other treatment at the end of incubation for both soils. The Woburn soils could more easily suffer from the leaching of nitrate because the soils were more permeable and more N was mineralized during the incubation compared to the Rothamsted soils.     

Evaluation of a nitrogen transport and transformation model in a bare soil

Simulation models are useful tools to understand the interaction between the transformation and the transport of nitrogen in the field. This study was done to calibrate, test and analyse a mechanistic, one‐dimensional model that describes the transport and transformations of nitrogen in the soil. The physical module describes transport of water, heat and solute, and the biological module simulates transformations of C and N with a restricted number of measurable organic pools. The calibration was based mainly on laboratory experiments independent of those used to evaluate the model. The evaluation procedure used field data collected on a bare loamy soil. The profiles of water content, water potential, temperature, chloride and nitrate (¹⁵N‐labelled and unlabelled) concentrations were measured from 0 to 150 cm continuously for 1 year. Simulated results were in good agreement with experimental data. However, some discrepancies were noticeable for chloride and nitrate concentrations in the deep layers. These differences were probably due to an underestimation of mass transport in the deep layers. A sensitivity analysis was carried out to determine the response to changes in some parameters in terms of mineralization, leaching and model efficiency. Mineralization is more sensitive to biological factors whereas nitrate leaching is more sensitive to initial and boundary conditions and hydraulic parameters. The experiment ran for only 1 year, which was too short a time to test biological factors.     

Deep incorporation of corn straw benefits soil organic carbon and microbial community composition in a black soil of Northeast China

‘Deep incorporation of corn straw’ (CSDI) is to concentrate the burial of corn straw into the subsurface soil layer (20–40 cm) and to break the plough pan, thereby creating a loosened plough layer (0–20 cm) and a fertile subsurface soil layer. However, its impacts on soil organic carbon (SOC) and the microbial community remain poorly understood. A field experiment was conducted to investigate the effects of 1-year CSDI (CD1), 3-year CSDI (CD3) and 5-year CSDI (CD5) on soil aggregates and aggregate-associated SOC, as well as bacterial and fungal community characteristics (examined by the high-throughput gene sequencing method). The results demonstrated that SOC and soil fungal diversity were decreased by CD1, but increased by CD3 and CD5. Compared with the control, CD5 promoted 2–0.25 mm soil macroaggregation, significantly increased SOC by 8.94% and aggregate-associated SOC by 5.96%–8.84%, consequently improving the physical protection of SOC by soil aggregates. CD3 and CD5 enhanced the richness and diversity of soil bacteria and fungi, and altered community composition. For soil bacteria, the relative abundance of Acidobacteria and Chloroflexi was increased, while that of Firmicutes, Gemmatimonadetes, Sphingomonas and Bacillus was decreased. For soil fungi, the relative abundance of Ascomycota, Zygomycota, Mortierella and Fusarium was greatly improved, but that of Basidiomycota was reduced. These obvious variations in microbial community structure were beneficial to straw degradation and SOC accumulation. Overall, the optimization of microbial community with CSDI plays a positive role in promoting soil organic matter, nutrient cycling and carbon sequestration, and thus improving soil fertility.     

秸秆还田对吉林黑土区土壤有机碳、氮的影响

秸秆是农业生产的重要有机肥来源之一,研究其还田过程中土壤有机碳、氮的变化,对了解土壤质量的改变具有重要意义。2011年5～9月作物生长期间,对黑土区不同秸秆全部还田、秸秆全部还田+化肥(C:N=1:10)、秸秆全部还田+化肥(C:N=1:20)后,土壤有机碳、氮的变化研究结果显示,与秸秆未还田(对照)相比,秸秆全部还田(C1.0)条件下土壤pH与土壤湿度略有降低,其他指标则相应增加;含有秸秆的处理中,土壤有机碳、pH、土壤呼吸强度、土壤温度变化趋势均为C1.0>C/N10>C/N20。土壤呼吸强度、土壤温度、湿度变化随着时间呈下降趋势。主成分分析显示,秸秆还田有利于改善土壤有机碳、全氮以及C/N等。     

Effects of repeated straw incorporation on crop fertilizer nitrogen requirements, soil mineral nitrogen and nitrate leaching losses

Abstract. The effects of straw disposal by burning and incorporation on soil and crop nitrogen (N) supply, were investigated on two light textured soils in central (ADAS Gleadthorpe) and eastern England (Morley Research Centre) over the period 1984 to 1995. Nitrogen balance calculations showed that after 11 years of contrasting straw incorporation versus burn treatments, the cumulative N returns in straw were c . 570kg/ha at Gleadthorpe and c . 330 kg/ha at Morley However, these N returns via straw incorporation were not reflected in increased total soil N levels in autumn 1994. There were no differences ( P > 0.05) between straw disposal treatments in autumn soil mineral N supply, readily mineralizable N or organic carbon. Similarly, there were no consistent differences between the treatments in terms of crop yield, crop N uptake or optimum fertilizer N rates. Fertilizer N applications of 200 kg N/ha/y increased topsoil organic carbon from 1.18 to 1.28% and total N content from 0.091 to 0.102% on the loamy sand textured soil at ADAS Gleadthorpe, but not at Morley. Previous fertilizer N applications increased the quantity of nitrate-N leached in drainage water by c . 20 kg/ha at Gleadthorpe and c . 60 kg/ha at Morley overwinter 1994/95, and by 10–20 kg/ha at both sites overwinter 1995/96. There was some indication overwinter 1994/95 that straw incorporation reduced nitrate-N leaching by 10–25 kg/ha, but there were no differences between treatments overwinter 1995/96.     

稻草还田对土壤氮素矿化及烟叶品质的影响

探索调控土壤供氮的措施,是降低上部烟叶烟碱含量,提高我国烟叶整体质量的关键问题.以云南水旱轮作植烟土壤为研究对象,通过大田原位培养试验,研究了稻草覆盖还田和稻草翻埋还田对土壤氮素矿化及烟叶品质的影响.结果表明,稻草还田提高了土壤供氮能力,稻草还田方式不同对土壤氮素矿化的影响有所差异.在烤烟旺长期,稻草覆盖还田明显增加了土壤氮素矿化量;采收期,稻草翻埋还田处理的土壤氮素矿化量增加显著.在烟株整个生育期,稻草覆盖还田和稻草翻埋还田处理的土壤累积矿化量分别达到139 kg/hm2和129 kg/hm2,比对照处理分别增加了20.4%和12.2%.由此说明,稻草覆盖还田对土壤氮素矿化的促进作用更显著.尽管稻草还田促进了土壤氮素矿化,增加了土壤供氮量,但两种稻草还田方式均显著降低了上部烟叶总氮和烟碱浓度,提高了其总糖和还原糖浓度,改善了上部烟叶品质.其中,两种还田方式的影响差异不大,总氮含量和烟碱浓度约降低18%和17%,总糖和还原糖浓度约增加23%和19%.稻草还田对中部烟叶品质的影响不显著.     

Grassland plants affect dissolved organic carbon and nitrogen dynamics in soil

Dissolved organic carbon (DOC) and nitrogen (DON) are central in many nutrient cycles within soil and they play an important role in many pedogenic processes. Plants provide a primary input of DOC and DON into soil via root turnover and exudation. Under controlled conditions we investigated the influence of 11 grass species alongside an unplanted control on the amount and nature of DOC and DON in soil. Our results showed that while the presence of plants significantly increases the size of a number of dissolved nutrient pools in comparison to the unplanted soil (e.g. DOC, total phenolics in solution) it has little affect on other pools (e.g. free amino acids). Grass species, however, had little effect on the composition of the DOC, DON or inorganic N pools. While the concentration of free amino acids was the same in the planted and unplanted soil, the flux through this pool was significantly faster in the presence of plants. The presence of plants also affected the biodegradability of the DOC pool. We conclude that while the presence of plants significantly affects the quantity and cycling of DOC and DON in soil, comparatively, individual grass species exerts less influence.     

长期稻草还田对土壤球囊霉素和土壤C、N的影响

A long-term experiment was conducted to investigate how long-term fertilization and rice straw incorporation into soil affect soil glomalin, C and N. The combined application of chemical fertilizer and straw resulted in a significant increase in both soil easily extractable glomalin （EEG） and total glomalin （TG） concentrations, as compared with application of only chemical fertilizer or no fertilizer application. The EEG and TG concentrations of the NPKS （nitrogen, phosphorus, and potassium fertilizer application ＋ rice straw return） plot were 4.68% and 5.67% higher than those of the CK （unfertilized control） plot, and 9.87% and 6.23% higher than those of the NPK （nitrogen, phosphorus, and potassium fertilizer applied annually） plot, respectively. Application of only chemical fertilizer did not cause a statistically significant change of soil glomalin compared with no fertilizer application. The changes of soil organic C （SOC） and total N （TN） contents demonstrated a similar trend to soil glomalin in these plots. The SOC and TN contents of NPKS plot were 15.01% and 9.18% higher than those of the CK plot, and 8.85% and 14.76% higher than those of the NPK plot, respectively. Rice straw return also enhanced the contents of microbial biomass C （MBC） and microbial biomass N （MBN） in the NPKS plot by 7.76% for MBC and 31.42% for MBN compared with the CK plot, and 12.66% for MBC and 15.07% for MBN compared with the NPK plots, respectively. Application of only chemical fertilizer, however, increased MBN concentration, but decreased MBC concentration in soil.     

田间管理措施对土壤有机碳含量影响的模拟研究

利用农业生态系统生物地球化学模型(DNDC),选择6个典型的种植模式点,在特定的土壤和气候条件下运行模型,考察在其它投入条件不变的情况下,改变田间管理措施(秸秆还田、增施有机肥、改变化肥施用等)对土壤有机碳(SOC)含量影响的长期效应.研究结果表明,在众多的管理措施中,增加秸秆还田比例的固碳效应在众多的农田管理措施中体现最突出,以基本管理措施20年后有机碳含量为对照,当秸秆还田率增加到80%时,齐齐哈尔、平凉和芷江地区增加的SOC含量都在C 3 000 kg/hm2以上,北京郊区、江宁和盐亭地区每公顷则可以增加C10 000 kg以上.化肥增加SOC含量是通过增加作物还田残茬来实现的,与基本措施相比,除了华北和华东地区增施化肥使SOC含量显著增加外,其它地区均不明显.化肥施用量为本底值的50%配合秸秆还田率50%和化肥施用量为本底值的50%增施有机肥C 1 000 kg/hm2的两项措施,在各个地区都表现出比基本管理措施能存储更多的碳素,因此,在我国现在措施下,减少化肥的同时增加秸秆还田比例和增施有机肥是既增加土壤有机碳含量又减少化肥污染的"双赢"措施.     

稻草和紫云英联合还田下施氮水平对水稻产量及土壤氮素形态的影响

  【目的】  紫云英和稻草联合还田时其有机成分的分解和释放具有互补性。研究紫云英和稻草联合还田条件下水稻的适宜施氮水平,为稻田绿肥和稻草联合还田后优化养分管理提供依据。  【方法】  两年定位试验位于江汉平原稻区,在稻草全量还田基础上,设置冬季种植并翻压紫云英和冬闲两种模式。水稻季氮肥处理设不施氮 (N0) 和常规施氮量 (N 165 kg/hm2) 的50% (N50)、100% (N100) 和150% (N150) 共4个水平,以不施氮、冬闲和稻草不还田作为空白对照,共9个处理。测定水稻籽粒产量、氮含量及累积量,分析耕层土壤无机氮及有机氮组分。  【结果】  在稻草和紫云英联合还田条件下,减少常规氮肥量的50% (SMN50) 获得的稻谷产量较稻草单独还田的SN50处理高21%～23%,与联合还田或稻草单独还田下的SMN100、SMN150、SN100、SN150处理之间没有显著差异。稻草和紫云英联合还田的SMN0、SMN50、SMN100处理的稻谷氮累积量均显著高于对应的稻草单独还田处理 (SN0、SN50、SN100),增幅分别为65%、27%和22%。水稻收获后各处理间土壤全氮、非酸解性氮含量差异不显著,酸解性氮含量有差异,在N150处理下,稻草单独还田处理 (SN150) 的土壤酸解性氮含量显著高于稻草和紫云英联合还田处理 (SMN150);在酸解性氮组分中,SN150处理的未知酸解态氮成分的含量显著高于稻草单独还田的其他处理及所有稻草和紫云英联合还田处理。  【结论】  减少常规施氮量的50%情况下,与稻草单独还田处理相比,稻草和紫云英联合还田可显著增加稻谷氮素累积量、提高水稻产量,而保持常规施氮量和提高施氮量不能增加水稻的氮素吸收和产量;紫云英与稻草联合还田可以改善土壤氮素的有效性,显著降低高施氮量下稻草单独还田带来的酸解性氮组分中未知态氮的残留量。     

Response of soil microbial biomass to straw incorporation

The response of the soil microbial biomass to cereal straw incorporation was assessed for three sites in Eastern Scotland. Increases in the C:N ratio of the biomass, due to straw inputs, were greater for soil with a history of straw incorporation than soil with no previous incorporation history. The biomass C:N ratio response to straw inputs was associated with increases in the fungal component of soil microbial respiration, fungal plate count (total and cellulolytic) and FDA-active lengths of fungal hyphae.     

Biochar addition mitigates nitrogen loss induced by straw incorporation and nitrogen fertilizer application

Biochar has been shown to be potentially beneficial for enhancing yields and soil properties, and diminishing nitrogen (N) losses. However, it remains unclear how biochar regulates soil carbon (C) and N to mitigate N losses induced by straw mixing with N fertilizer in dryland soils. Therefore, we investigated the effects of straw mixing (S₁), S₁ with biochar (SB) and no straw inputs (S₀), and routine urea application rates (N₁) and 70% of routine rates (N_0.7) on yields and N losses, and identify the relationship between N losses and soil C and N compounds. Results showed that N_0.7 and N₁ were suitable for the maize and wheat seasons, respectively, contributing to mitigating N losses without reducing crop yields. Moreover, in the maize season, N_0.7-SB significantly mitigated the straw-induced NH₃-N and N₂O-N emissions by 106% and 81%, respectively. In the wheat season, N₁-SB reduced the straw-induced NH₃-N and N₂O-N emissions by 35% and 66%, respectively. In addition, N_0.7-SB sharply reduced soil inorganic N (SIN) storage in the maize season. Furthermore, the NH₃-N and N₂O-N emission rates were negatively correlated with dissolved organic carbon/SIN content (0–20 cm) (DOC/SIN_0-20). N losses (N₂O-N and NH₃-N emissions and SIN storage) were positively correlated with SIN_0-20, but negatively correlated with soil organic carbon / SIN_0-20 (SOC/ SIN_0-20). This study provides further evidence that biochar with an appropriate N application rate decreased SIN_0-20 and increased DOC/SIN_0-20, thus reducing SIN storage and the straw-induced gaseous N emissions without decreasing crop yields.     

水肥条件与稻草还田对土壤供氮及水稻产量的影响

通过2年田间裂区试验,研究了不同灌溉和施肥条件下,稻草还田对土壤供氮特征及产量的影响。结果表明：（1）上年晚稻稻草还田提高了来年早稻期间土壤NH4^＋-N浓度;配施氮肥后,新鲜早稻稻草还田也增加了晚稻期间土壤NH4＋-N浓度,但在不施氮肥情况下,淹水灌溉稻草还田处理的土壤NH4^＋-N浓度要低于移走稻草处理,间歇灌溉下稻草还田处理的土壤NH4^＋-N浓度仍高于移走稻草处理。（2）稻草还田能促进水稻中后期植株对氮素的吸收及生物量的累积。（3）稻草还田能增加水稻产量,早稻增产幅度为6.85%,晚稻为8.17%;施用氮肥后稻草的增产效应要显著高于不施氮肥,早、晚稻增产分别为9.18%和5.83%。稻草还田主要通过影响有效穗数来影响产量。水稻生长季节、灌溉模式和施肥条件对稻草还田的增产效应存在交互作用,早稻的最佳处理组合为“连续淹灌＋稻草还田＋配施氮肥”,晚稻的最佳处理组合为“间歇灌溉＋稻草还田＋配施氮肥”。