Co-incorporation of green manure and rice straw improves rice production, soil chemical, biochemical and microbiological properties in a typical paddy field in southern China

The cultivation of green manure or rice straw returns in southern China increases crop yields and soil fertility. Few studies have reported the effects of combining both management techniques on rice performance and soil fertility. A 3-year field study was carried out to analyse the impacts of the co-incorporation practice on soil microbial and biochemical parameters as well as crop yield. Five treatments were tested: (i) no-fertilizer (CK); (ii) chemical fertilizer (F); (iii) F plus green manure (FM); (iv) F plus rice straw (FS); (v) F plus green manure plus rice straw (FMS). The results showed that incorporation of green manure and/or rice straw increased double rice yields by 4.1% (FM), 4.7% (FS) and 9.6% (FMS) compared with F. The FMS treatment enhanced soil organic C (SOC), total N (TN), mineral N (Nₘᵢₙ), and available K (AK) levels by combining the advantage of FM in increasing TN and Nₘᵢₙ and the advantage of FS in increasing SOC and AK in comparison with F. The incorporation of green manure and/or rice straw stimulated microbial growth (total phospholipid fatty acids, PLFAs) and altered the soil microbial community structure relative to F, in which FMS had the greatest effect. The enzyme activities of β-glucosidase, β-cellobiosidase, N-acetyl-glucosaminidase, L-leucine aminopeptidase and phosphatase were higher in the green manure and/or rice straw application treatments than in the F treatment in the order FM ≈ FS < FMS. The partial least squares path model (PLS-PM) analysis indicated that green manure mainly influenced the abovementioned indices in the early rice season, while the effects of rice straw lasted until the late rice season. Our results suggest that co-incorporation of green manure and rice straw is a more effective practice for improving soil fertility and rice yields.