The Effects of Different Tillages on Crop Residue Sequestration, Soil Available Nutrients and Some Biochemical Properties in the Chinese Black Soil Region

Three-year field experiments were conducted to investigate the effects of different tillage operations after harvest on crop residues sequestration and their subsequent effects on soil available nitrogen (N), phosphorus (P), some soil biochemical properties, and three enzymatic activities during the following growing seasons in a soybean (Glycine max)-soybean-corn (Zea mays) rotation farming system in Northeast China. Two different managements were implemented after crop harvest every year, which were tillage (T) and no tillage (NT). Results showed that crop residue masses on soil surface and in the 0-20 cm layer after soybean harvest were about 1 450 and 340 kg ha⁻¹, respectively, in October 2006 and 2007. While, soybean residue mass in the 0–20 cm soil layer was about 340 kg ha⁻¹ in NT and about 1 550 kg ha⁻¹ in T before sowing in May 2007 and 2008. The adverse results were found after corn crop plantation, that corn residue mass was about 270 and 860 kg ha⁻¹ on soil surface and in the 0–20 cm soil layer, respectively, after harvest in October 2008, while residue mass in the 0–20 cm soil layer was only 466 kg ha⁻¹ in T but 863 kg ha⁻¹ in NT before planting in May 2009. So T had effectively sequestered soybean residue into soil but not corn. Results also showed that T after harvest helped to improve soil available N, P, soil microbial biomass carbon (MBC), and nitrogen (MBN) contents and soil enzymes activities (urease, acid phosphatase, and protease) during the 2007 and 2008 seasons, but the positive effects decreased during the 2009 season. T practice had significant positive effects on available N, P, MBC, and MBN contents, protease and urease activities, however, no obvious effects on acid phosphatase activity. In this study, T practice after soybean harvest was proved to be preferable to improve soil microbial and enzyme activities during the following seasons due to an efficient sequestration of soybean residues. However, NT could be considered preferential after corn crop harvest.