Organic fertilizer substitution enhances maize yield and quality under reduced irrigation

Reduction of 20% irrigation combined with organic fertilizer substitution at 25% of chemical nitrogen (I1F2) enhanced maize yield and quality I1F2 improved maize yield and quality by regulating the photo-physiological traits and nitrogen transportation I1F2 had the highest comprehensive evaluation index of maize. Ensuring an adequate and nutritious food supply for the global population is a significant challenge in agricultural production practice. Water and fertilizer are the main limiting factors in improving crop yield and quality. However, organic fertilizer substitution with partial chemical nitrogen combined with irrigation reduction can increase maize yield and quality, through improvements in photo-physiological traits and nitrogen transportation, remains unclear. A split plot field experiment of maize was established in an arid area of northwestern China from 2021 to 2023. Two irrigation levels formed the main plot, local conventional irrigation (I2, 4,050 m 3 ha −1 ) and reduced by 20% (I1, 3,240 m 3 ha −1 ). Five equivalent nitrogen substitution ratios of chemical nitrogen with organic fertilizers formed split plot, including sole chemical nitrogen fertilizer (F1), organic fertilizer substituting at 25% (F2), 50% (F3), 75% (F4), and 100% (F5) of chemical nitrogen fertilizer. Discussing the effect of maize yield, quality, photo-physiological traits, and nitrogen transportation with combining organic and chemical nitrogen fertilizers under reduced irrigation. The results showed that reduced irrigation decreased maize yield and quality. However, organic fertilizer substitution at 25% of chemical nitrogen increased maize yield and quality, with this effect greater than other equivalent nitrogen substitution ratios of chemical fertilizer with organic fertilizer. Reduced by 20% irrigation combined with organic fertilizer substitution at 25% of chemical nitrogen (I1F2) increased maize grain yield and biomass by 13.0 and 8.9% compared to local conventional irrigation and sole chemical nitrogen fertilizer (I2F1). Meanwhile, I1F2 improved grain protein by 10.0%, enhanced amino acid and vitamin B contents by 60.4 and 30.6%, and raised straw crude fat and crude protein contents by 23.1 and 5.6% compared to I2F1 in maize, respectively. The reason for improving maize yield and quality with I1F2 was attributed to (1) improving leaf area index and leaf area duration at the R2−R4 stage by 6.2 and 4.1%, increasing net photosynthetic rate by 43.8%, and enhancing the activities of pyruvate phosphate dikinase, phosphoenolpyruvate carboxykinase, and Rubisco activities by 9.8, 9.7, and 10.5%, respectively; (2) promoting nitrogen uptake and nitrogen accumulation after the R1 stage by 5.6 and 5.4% while maintaining nitrogen transportation quantity before the R1 stage. Therefore, reduced irrigation by 20% combined with organic fertilizer substitution at 25% of chemical nitrogen can improve maize yield and quality via improving photo-physiological traits and nitrogen transportation in arid irrigation areas.