秸秆还田对农田黑土团聚体稳定性及孔隙结构的影响

Effect of straw incorporation on the stability and pore structure of aggregates in the black soil

团聚体作为土壤基本单元,其孔隙结构影响着土壤中的水、肥、气、热,进而影响着土壤生产力。为探究秸秆还田对黑土团聚体的影响,依托中国科学院海伦农田生态系统国家野外科学观测研究站9年秸秆还田试验,设置了6 000 kg·hm^(-2)(S1)、9 000 kg·hm^(-2)(S2)、12 000 kg·hm^(-2)(S3)和15 000 kg·hm^(-2)(S4)4个玉米秸秆还田处理,以无秸秆还田为对照(CK),采用湿筛法和显微CT扫描研究水稳性团聚体分布情况和3~5 mm团聚体孔隙结构特征。结果表明,S4、S3、S2、S1水稳性大团聚体(>0.25 mm)含量与CK相比分别增加120%、92.1%、73.2%、40.4%。S2、S3、S4与CK、S1相比,平均重量直径(MWD)增加13.0%~29.6%(P<0.05)。S4几何平均直径(GMD)相较于CK、S1和S2分别增加35.1%、 25.0%和8.70%(P<0.05),通气孔隙(ED>100μm)相较于S1、 S2分别提高了272%和137%(P<0.05)。S3分形维数与CK、S1相比增加了22.1%和7.97%,S4分形维数与CK、S1、S2相比增加了26.1%、11.6%和6.06%(P<0.05)。与秸秆未还田(CK)处理相比,秸秆还田(S1、S2、S3、S4)处理连通性明显较好,但S3与S4之间分形维数和连通性差异不显著。因此,玉米秸秆还田不仅能提升团聚体稳定性,还能改善团聚体孔隙结构,提高孔隙复杂性和连通性,是一项提升土壤肥力、改善土壤结构和保育黑土的有效技术措施,在东北黑土区具有较好的应用前景。

Soil aggregate is an important component of soil,its pore structure affects the water,fertilizer,air and heat in the soil,and thus affects the productivity.In order to quantify the impact of straw returning on black soil aggregates,based on the 9-year straw returning experiment conducted in the national field scientific observation and research station of Hailun farmland ecosystem,Chinese Academy of Sciences,4 maize straw returning treatments of 6000 kg·hm^(−2)(S1),9000 kg·hm^(−2)(S2),12000 kg·hm^(−2)(S3)and 15000 kg·hm^(−2)(S4)were set up,with no straw returning as the control(CK).Wet screening method and CT scanning were used to study the distribution of water stable aggregates and the pore structure characteristics of 3~5 mm aggregates.The results showed that compared with CK,the content of water stable macro-aggregates(>0.25 mm)in S4,S3,S2 and S1 increased by 120%,92.1%,73.2%and 40.4%.Compared with CK and S1,the mean weight diameter(MWD)of S2,S3 and S4 increased by 13.0%~29.6%(P<0.05).Compared with CK,S1,and S2,the geometric mean diameter(GMD)of S4 increased by 35.1%,25.0%and 8.70%(P<0.05),and the aeration pore(ED>100μm)compared with S1 and S2,it increased by 272%and 137%(P<0.05).The fractal di-mension of S3 increased by 22.1%and 7.97%compared with CK and S1,and the fractal dimension of S4 increased by 26.1%,11.6%and 6.06%compared with CK,S1 and S2(P<0.05).Compared with CK treatment,the connectivity of straw returning treatment(S1,S2,S3,S4)was significantly better,but there was no significant difference in fractal dimension and connectivity between S3 and S4.Therefore,returning corn straw to the field can not only improve the stability of aggregates,but also improve the pore structure of aggregates,improve the complexity and connectivity of pores.It is an effective technical measure to enhance soil fertility,improve soil structure,and conserve black soil,and has a good application prospect in the black soil area of Northeast China.