Impacts of one-time large amounts of leafy vegetable waste incorporated into dryland fields on soil fertility and forage maize production

Abstract

A large amount of vegetable waste is often dumped into the environment, causing serious pollution in major market distribution areas. This paper explores the feasibility and optimization of incorporating vegetable waste into dryland fields to improve soil fertility and crop productivity. The experimental design included three quantities of fresh leafy vegetable waste (QVW) buried into the soil: 800, 1600, and 2400 t·ha−1 and three covering soil thicknesses (CST): 10, 20, and 30 cm. Zero QVW was the control NW. By planting forage maize for two consecutive years, the variations of soil parameters and aboveground dry biomass (ABM) of maize plants were observed. Compared with the NW, the incorporation led to a distinct decline in soil bulk density (BD) by 2.00–17.41%, an increase in soil moisture (SM), organic carbon (SOC), total nitrogen (TN), and microbial carbon (MBC) by 5.84% −29.72%, 5.93% −50.17%, 16.98% −245.71% and 19.66% −304.08%, respectively. Topsoil conductivity (EC) and soil inorganic nitrogen (IN) were 3.81–9.43 fold and 19.02–88.29 fold that of NW. BD was significantly negatively correlated with the QVW and CST. SM, SOC, TN, and IN increased significantly with the increase of QVW and CST. The topsoil EC was significantly positively correlated with QVW, and negatively correlated with CST. The sequestration rates of SOC and nitrogen were significantly positively correlated with CST. The ABM in the incorporating vegetable waste treatment was 1.59–2.74 fold that of NW. The ABM showed a parabolic relationship with QVW (R2 = 0.97 **), and a linear relationship with CST (R2 = 0.91 **). Conclusively, the optimal QVW was 1346 t·ha−1, and the corresponding CST was 30 cm. Excessive QVW can cause topsoil salinization and constrain crop growth. Increasing CST contributes to sequestrating more water and nutrients and mitigating secondary salinization of the soil.