沼液替代化肥及与秸秆联用对稻田土壤反硝化和硝态氮氨化潜力的影响

Effects of Substitution of Chemical Fertilizer with Biogas Slurry and Combined with Straw on Denitrification and Nitrate Ammoniation Potential of Paddy Soil

为揭示沼液替代化学氮肥及与秸秆联用对土壤反硝化(Denitrification,Den)和硝态氮氨化(Dissimilatory nitrate reduction to ammonium,DNRA)特征的影响,以江苏东台典型滨海稻田为对象,进行田间小区实验,设置单施化肥(C)、单施沼液(B)、沼液秸秆联用(BS)和化肥秸秆联用(CS)以及对照(CK)5个处理,借助15N同位素示踪技术研究水稻不同生育期各处理土壤Den和DNRA潜力的变化特征。结果表明:(1)整个水稻生育期内,沼液替代化肥可有效降低稻田土壤Den强度(1.48μg·kg^(-1)·h^(-1)),N2O总生成量减少27%,但沼液秸秆配施与化肥秸秆配施相比导致N2O生成总量显著增加70%。(2)从不同生育期看,成熟期N2O的调控显得尤为必要。沼液处理(B、BS)与化肥处理(C、CS)均在成熟期出现N2O产生高峰,平均占总产生量的70%~71%与75%~92%。沼液替代化肥有利于氮素在土壤的保存,分蘖期土壤DNRA潜力最高,并且B和BS处理DNRA潜力显著高于C和CS处理。(3)相关性分析发现,单施沼液或化肥处理Den潜力均与pH正相关,与C:N负相关,其中C:N的升高是沼液替代化肥(即B处理)Den强度降低的重要原因。配施秸秆,主导Den潜力变化的因子转变为 NO_(3)^(-)-N和 NH_(4)^(-)-N,且C︰N的降低导致Den强度增加。本研究明确了沼液替代化肥与秸秆还田对稻田土壤Den、DNRA过程的影响及其环境效应评估,并为滨海农田沼液施用模式的探索提供一定理论依据。

【Objective】This study aimed to reveal the effects of biogas slurry instead of chemical nitrogen fertilizer on soil Denitrification(Den)and Dissimilatory nitrate reduction to ammonium(DNRA).【Method】A field plot experiment was carried out in a typical coastal paddy field in Dongtai,Jiangsu Province.Five treatments were set up:a single application of chemical fertilizer(C),a single application of biogas slurry(B),combined application of biogas slurry and straw(BS),combined application of chemical fertilizer and straw(CS)and control(CK).The variation characteristics of soil Den and DNRA potential at different growth stages of rice plants were studied by the 15N isotope tracer technique.【Result】The results showed that:(1)In the whole rice growth period,Biogas slurry instead of chemical fertilizer effectively reduced the Den intensity(1.48μg·kg–1·h–1)and the total amount of N2O by 27%in paddy soil.Compared with the combined application of chemical fertilizer and straw,the combined application of biogas slurry and straw resulted in a significant increase in total N2O(70%).(2)Looking at different growth stages,the regulation of N2O in the mature stage of the plant is particularly necessary.The N2O production in biogas slurry(B,BS)and chemical fertilizer(C and CS)treatments peaked at maturity,accounting for 70%~71%and 75%~92%of the total production on average,respectively.Also,the soil DNRA potential was the highest at tillering stage,and the DNRA potential of B and BS treatments were significantly higher than that of C and CS treatments.(3)The Den potential of biogas slurry or chemical fertilizer treatment was positively correlated with pH and negatively correlated with C:N.Also,the increase in C:N resulted in a decrease in Den intensity of biogas slurry instead of chemical fertilizer(i.e.treatment B).When combined with straw,the factors leading to changes in Den potential are transformed into NO_(3)^(-)-N and NH_(4)^(+)-N,and the decrease of C:N leads to an increase in Den intensity.【Conclusion】Biogas slurry instead of chemical fertilizer can play a positive role in the preservation of nitrogen in soils.This study provides a theoretical basis for clarifying the impact of biogas slurry replacing chemical fertilizer and straw returning on the process of Den and DNRA in paddy soils.Also,it highlights the environmental impact as well as the exploration of biogas slurry application mode in coastal farmland.