秸秆还田方式对草甸土有机碳和硝态氮分布特征的影响

Effects of Straw Returning Methods on Distribution Characteristics of Organic Carbon and Nitrate-N in Meadow Soil

[目的]研究不同耕法与秸秆还田方式下草甸土不同深度土层中有机碳(SOC)和硝态氮(N)的分布特征,为有效利用秸秆培肥土壤提供依据。[方法]采用田间定位试验,研究3种耕法(免耕、浅翻、深翻)与3种秸秆还田方式(覆盖还田、浅翻还田、深翻还田)条件下,不同时期、不同深度土层中SOC与硝态N的变化。[结果]无论秸秆是否还田,不同耕法下土壤硝态N含量随生育进程均表现为先升高再降低的趋势,苗期>成熟期>播种期;无秸秆还田条件下,3种耕法处理土壤硝态N含量随土层深度增加而降低,40~50 cm土层均没有出现硝态N富集现象,浅翻与深翻分别对10~20和20~30 cm土层硝态N含量影响较明显;深翻处理0~30 cm土层SOC含量比免耕和浅翻分别降低8.75%、9.53%;秸秆还田条件下,不同时期土壤硝态N总积累量不同。苗期以深翻还田处理积累量较大,比浅翻还田和免耕覆盖分别增加8.15和9.57 mg/kg;成熟期硝态N总积累量以免耕覆盖处理最大,比浅翻还田和深翻还田分别提高19.23%和14.68%;深翻还田30~40 cm土层SOC含量比免耕覆盖和浅翻还田分别增加3.33和3.86 g/kg。[结论]同一耕法,短期内连续有秸秆还田处理土壤硝态N含量低于无秸秆还田处理,秸秆还田深度影响不同深度土层中SOC的含量。

[Objective]The research aimed to study the distribution characteristics of organic carbon(SOC)and nitrate nitrogen(N)in different depths of meadow soil under different tillage methods and straw returning methods,and provide a basis for effective use of straw to fertilize soil.[Method]Field positioning experiment was conducted to study the changes of SOC and nitrate-N in soil layers of different periods and depths under the conditions of three kinds of tillage methods(no-tillage,shallow tillage,deep tillage)and three kinds of straw returning methods(covering returning fields,shallow tillage turning field,deep tillage turning field).[Result]The trend of soil nitrate-N content was increased first then decreased with the growth process whether the straw was returned to the field,seedling stage>maturation period>sowing date.The soil nitrate-N distribution under three kinds of tillage was decreased with the depth of soil layer decreasing without straw,and there was no nitrate-N enrichment in 40-50 cm soil layer in the short term,at the same time the nitrate-N content in 10-20 cm and 20-30 cm soil layers was respectively influenced by shallow tillage and deep tillage.The SOC content was effected at deep tillage in 0-30 cm soil layer,which was lower 8.75%and 9.53%than that in no-tillage and shallow tillage.After the straw was returned to soil,the total accumulation of soil nitrate N in different periods was different.In the seedling stage,the accumulation of nitrate-N in the deep tillage turning field was larger,which was 8.15 and 9.57 mg/kg higher than that of shallow-turning and no-tillage.But in the mature period,it was the largest in the no-tillage treatment,which was 19.23%and 14.68%higher than that of the shallow tillage turning field and the deep tillage turning field.The SOC content with deep tillage turning field in 30-40 cm soil layer was higher 3.33 and 3.86 g/kg separately than no-tillage and shallow tillage turning field.[Conclusion]In the same tillage method,the soil nitrate N content in the short-term continuous straw returning treatment was lower than that without straw returning,and the straw returning depth affected the SOC content in different depth soil layers.