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

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 6 000 kg·hm⁻² (S1), 9 000 kg·hm⁻² (S2), 12 000 kg·hm⁻² (S3) and 15 000 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="">100 μm) compared with S1 and S2, it increased by 272% and 137% (P<0.05). The fractal dimension 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.