Optimizing maize yield and mitigating salinization in the Yellow River Delta through organic fertilizer substitution for chemical fertilizers

Abstract

Improper fertilization and irrigation practices are recognized as primary contributors to the exacerbation of secondary salinization in agricultural soils. Substituting chemical fertilizers with organic fertilizers is considered an effective strategy to mitigate secondary salinization, improve saline-alkali soils, and enhance crop yields. However, the specific effects and underlying mechanisms of reducing chemical fertilizer application in combination with organic fertilizers in saline-alkali conditions remain insufficiently understood. This study focuses on summer maize grown in coastal saline-alkali areas, employing various proportions of organic fertilizer substitution (10 %, 20 %, 30 %, 40 %) to identify an optimal application model. The findings reveal that the application of organic fertilizer as a partial substitute for chemical fertilizer directly alters the contents of alkali-hydrolyzed nitrogen, available phosphorus, available potassium, and soil quality water content in different layers, which in turn affects the total absorption of nitrogen, phosphorus, and potassium to varying degrees, thereby influencing the crop's grain yield and biomass yield. Compared to the conventional use of chemical fertilizers alone, the incorporation of organic fertilizers led to changes in grain yield and biomass yield, ranging from −13.14 % to 7.14 % and −4.86 % to −8.14 %, respectively. The soil contents of alkali-hydrolyzable nitrogen, available phosphorus, and quick-acting potassium changed by −8.30 % to 1.40 %, −13.19 % to –7.81 %, and −1.81 % to 8.42 %, respectively. Additionally, the total uptake of nitrogen, phosphorus, and potassium by maize varied by −10.03 % to 7.62 %, −10.95 % to –8.93 %, and −9.64 % to 21.95 %, respectively. Significant differences were observed in maize yield, soil nutrient levels, and plant nutrient utilization rates across the different proportions of organic fertilizer substitution. Notably, the highest maize yield was achieved when the substitution proportion was 30 %, suggesting this ratio as the optimal application model for maize production in the saline-alkali soils of the Yellow River Delta. These results provide a theoretical foundation for optimizing fertilizer management in maize cultivation within saline-alkali soils.