Effects of Different Biochar Application Rates on Soil Aggregate Characteristics and Organic Carbon Contents for Film-Mulching Field in Semiarid Areas

The aim of this study was to investigate the effects of long-term plastic film mulching farmland combined with different biochar input rates on soil aggregate stability and organic carbon in northwest China, in order to provide a scientific basis for improving the soil fertility and maintaining the sustainability of crop production for film-mulching field in semiarid regions.

Based on continuous years of double ridge furrow film mulching (D), the full film double ridge furrow mulching planting and traditional flat without film mulching planting were set as the main treatment, and four biochar input rates (no returning (N), 3 t·hm^-2 (L), 6 t·hm^-2 (M), and 9 t·hm^-2 (H) ) were set as the secondary treatment respectively to investigate the effects of different biochar input rates on soil aggregate distribution, aggregate stability, aggregate organic carbon and maize yield.

The film mulching could significantly (P<0.05) increase the soil mechanical stable (6.1%-8.7%) and water-stable macro-aggregate contents (15.9%-83.6%) and maize yield (35.0%-41.8%). Under the film mulching planting, biochar inputs treatments could significantly (P<0.05) increase mechanical macro-aggregate and water macro-aggregate by 6.8% and 29.6% on average, respectively, and the effects gradually increased with the increase of biochar inputs rate. In addition, biochar inputs could also increase the soil organic carbon and aggregate organic carbon content in film mulching farmland, and the effects under DH (9 t·hm^-2) were better than other treatments, with an average increased by 13.9% and 25.9%, respectively. Maize yield was significantly correlated with biochar addition rates ( λ=0.42, P<0.001 ), and DH had the highest yield with 12.8 t·hm^-2.

Biochar input could significantly improve soil aggregrate characteristics and organic carbon content in plastic film mulching farmland, thus increase the maize yield and promote soil carbon sequestration, especially with 9 t·hm^-2.