玉米秸秆还田对土壤团聚体组成及其碳氮分布的影响

Effect of Maize Straw Returning to Field on Soil Aggregates and Their Carbon and Nitrogen Distributions

为揭示玉米秸秆还田对土壤团聚体组成及其碳氮分布的影响,采用单因素随机区组设计,设置秸秆不还田(T0)、秸秆还田3000 kg·hm^-2(T1)、6000 kg·hm^-2(T2)、9000 kg·hm^-2(T3)、12000 kg·hm^-2(T4)5个处理,研究持续5 a秸秆还田条件下,秸秆还田量与土壤团聚体组成及其团聚体碳氮分布间的相互关系。结果表明:连续秸秆还田对土壤总碳、碱解氮、速效钾有显著影响。与T0相比,T3和T4处理土壤总碳提高4.29%、6.13%,土壤碱解氮含量提高11.41%、13.86%,土壤速效钾含量提高11.63%、14.89%。T4处理下土壤粒径大小为1~2 mm的水稳性团聚体百分含量与T0间差异显著,T3处理下土壤粒径大小为0.5~1 mm的水稳性团聚体百分含量显著低于T0。随秸秆还田量的增加,土壤平均重量直径(MWD)、水稳系数(K)增加。整体上,受持续秸秆还田影响,土壤水稳性团聚体中氮含量以T 3处理最高,但不同粒径的土壤水稳性团聚体中碳含量间差异不显著。多元分析表明:>5 mm粒径的土壤水稳性团聚体所占百分数与土壤MWD及K值间显著正相关;各粒径土壤水稳性团聚体中的全氮、总碳含量与土壤总碳含量均呈正相关。持续玉米秸秆还田提高土壤水稳性团聚体的MWD和K值,促进>5 mm粒径的土壤大团聚体的形成;土壤水稳性团聚体中氮含量的差异较碳更显著,氮更易富集。

To reveal the effect of continuous maize straw returning to the field on soil aggregate composition and the distribution of soil carbon and nitrogen in aggregates,we set up five treatments by the method of single factor randomized block design,including no straw returning to the field(T 0),straw returning to the field 3000 kg·hm^-2(T1),6000 kg·hm^-2(T2),9000 kg·hm^-2(T3)and 12000 kg·hm^-2(T4).The relationships among soil aggregate composition,the distribution of carbon,nitrogen in the aggregates and the amount of straw returning to the field were discussed.The results showed that soil total carbon,the available nitrogen and the available potassium were significant difference under the different treatment(P<0.05).Compared with control(T0),the contents of soil total carbon were increased by 4.29%and 6.13%,the contents of soil available nitrogen increased by 11.41%and 13.86%and the content of soil available potassium increased by 11.63%and 14.89%under T3 and T4 treatments,separately.The percentage of soil water-stable aggregates with particle size of 1-2 mm under T4 treatment was significantly different under T0 treatment.The percentage of soil water-stable aggregates with particle size of 0.5^-1 mm was also significantly lower in T3 than in T0.The mean weight diameter(MWD)and soil water stability coefficient(K)were enhanced with the increase of straw returning amount.On the whole,the soil nitrogen of water-stability aggregates was the highest in T 3,but there was no significant difference for soil carbon in different particle size of soil water-stable aggregates.The results of multivariate analysis showed thatthere was a significant positive correlation between the percentage of soil water-stable aggregates with particle size over 5 mm and soil MWD and K values.The contents of total nitrogen and total carbonin soil water-stable aggregates were positively correlated with the contents of soil total carbon.Insummary,the value of MWD and K of soil water-stable aggregates increased and the percentage of soil large aggregates(>5 mm in diameter)were promoted by the continuous application of maize straw after 5 years.The difference of the nitrogen contentin different particle size of soil water-stable aggregates were more significant than the soil carbon,and soil nitrogen was more easily accumulated in soil aggregate.