Key mechanisms underlying the enhancement of sweet maize yield through partial substitution of chemical fertilizers with organic manure in arid irrigation districts

This study investigated the effects of partially replacing chemical fertilizers with organic fertilizers on sweet maize yield in the oasis irrigation area and explores the underlying mechanisms, aiming to provide a theoretical basis for optimizing high-yield cultivation practices in this region. Field trials were conducted in the Northwest Oasis Irrigation District from 2023 to 2024, with five levels of organic fertilizer substitution: 0% (CK), 10% (M1), 20% (M2), 30% (M3), and 40% (M4). The study examined the effects of different substitution ratios on soil nutrients, photosynthetic characteristics, and sweet maize yield. Compared with CK, both M1 and M2 treatments enhanced sweet maize growth and soil nutrient accumulation, with M2 showing superior results. the M2 treatment increased dry matter accumulation (DMA), fresh ear yield (EY), and fresh grain yield (GY) by 11.17%, 4.51%, and 6.31%, respectively. Soil total nitrogen (TN), available phosphorus (AP), and available potassium (AK) increased by 28.23%, 7.07%, and 3.93%, respectively. Net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr) increased by 1.36%, 16.14%, and 34.34%, respectively, and all differences were statistically significant. Although M3 and M4 treatments increased stomatal conductance and transpiration rate, they reduced crop yield and soil nutrient content. Correlation analysis indicated that TN, soil organic matter (SOM), root biomass (RB), SPAD, leaf area index (LAI), DMA, AK, Tr, AP, and Pn are key factors influencing EY and GY. To clarify the regulatory pathways among these variables, partial least squares structural equation modeling (PLS-SEM) revealed that soil nutrients influence RB, which directly affects LAI and photosynthetic parameters. LAI and photosynthetic parameters, in turn, directly influence DMA, ultimately affecting EY and GY. In summary, replacing 20% of chemical fertilizer with organic fertilizer enhances yield by improving soil fertility and photosynthetic efficiency in sweet maize. This approach offers a rational strategy for organic-inorganic fertilizer management in oasis irrigation systems.