Film mulched ridge–furrow tillage improves the quality and fertility of dryland agricultural soil by enhancing soil organic carbon and nutrient stratification

Film mulched ridge–furrow tillage (FMRF) has been successfully used to replace conventional tillage (CT) and increase maize yields in drylands in northwestern China. To increase maize production sustainably, however, investigations are warranted of the underlying mechanism through which FMRF affects soil quality and fertility. Therefore, we conducted an 18-year survey (2003–2020) and a 6-year (2015–2020) field experiment to systematically compare CT and FMRF with regard to soil bulk density (BD) and the concentration, storage, and stratification of soil organic carbon (SOC); labile organic carbon (LOC); total nitrogen, phosphorus, and potassium (TN, TP, and TK, respectively); and available N, P, and K (AN, AP, and AK, respectively). Data were collected in a soil layer of 0–30 cm in the survey and in a soil profile of 0–100 cm with 20-cm increments in the field experiment. The SOC, N, P, and K storage, C:N ratio, and their surface stratification ratios were calculated, and their contributions to soil quality and fertility were systematically evaluated. The results indicated that BD decreased with increasing years of FMRF application. Compared to CT, FMRF significantly increased the concentrations of AK, AP, AN, TK, TP, TN, LOC, and SOC, especially at the 0–40 cm soil horizon and the storage of SOC, TN, TP, and TK in the entire 0–100 cm soil profile, but significantly decreased the C:N ratio at 0–60 cm depth. The stratification ratios of AK, AP, AN, LOC, TK, TN, TP, and SOC were within 1–2.5 and were significantly higher under FMRF than CT for 0–60 cm depth. FMRF also significantly improved soil water status and contributed greatly to increasing the concentration and redistribution of SOC, N, P, and K. Therefore, FMRF improved the soil quality and fertility by increasing the concentration and stratification of SOC, N, P, and K. Further investigations should systematically consider the integrated effects of soil types, farming system, soil microbial processes, and climatic factors.