Response of Maize Photosynthetic Production Capacity in Saline-Alkaline Soil to Organic Fertilizer Application Rates Under Differential Tillage Practices

Aiming at the problems of soil degradation and crop productivity limitation in saline-alkaline land in the Yinhuang Irrigation Area of Ningxia, this study aimed to investigate the effects of vertical deep rotary tillage with organic fertilizer on the production capacity of maize (Zea mays L.) in terms of photosynthesis material, so as to provide the theoretical basis for maize production in saline-alkaline land in the area.

This study was conducted in Pingluo, Ningxia, China, in 2021-2022. The maize cultivar Xianyu 1225 was used as the test material, and a split-zone experimental design was adopted, with the main zone being the tillage method (DT, vertical deep rotary tillage; TF, conventional tillage), and the subzones being the organic fertilizer dosage (M0, no fertilization; M1, 0.75×10⁴ kg·hm^-2; M2, 1.50×10⁴ kg·hm^-2; M3, 2.25×10⁴ kg·hm^-2). The photosynthesis and fluorescence parameters of maize leaves, dry matter accumulation and transport as well as the composition of maize yields at the maturity stage were measured at 10, 25, 60, 75, 95, and 120 d after seedling emergence, and the changes in the indexes of maize photosynthetic material production in the presence of the interactions between different tillage and organic fertilizer were analyzed, and then the effects of the tillage-fertilizer measures on the dry matter production of maize in saline and alkaline land were investigated.

(1) Compared with TF combined with M2, DT combined with M2 significantly increased the leaf area index (LAI) and photosynthetic potential (LAD), as well as photosynthetic and fluorescence parameters. Specifically, it enhanced: net photosynthetic rate (P_n) by 8.4%-35.0%, stomatal conductance (G_s) by 7.7%-19.8%, maximum photochemical efficiency of PSII (F_v/F_m) by 7.7%-17.1%, and potential maximum photosynthetic capacity of PSII (F_v/F_o) by 10.0%-30.3%. (2) DT combined with M2 significantly increased the maximum DMA rate (G_max) and mean DMA rate (G_mean), while optimally controlling the time to reach G_max (T_max) and active duration of DMA (D). It also enhanced the contribution rate of post-anthesis DMA to grain yield, which was conducive to high yield formation. (3) Correlation and principal component analysis (PCA) revealed that maize yield and G_mean showed significant or highly significant positive correlations with LAD, P_n, G_s, F_v/F_m and ABS/RC. Furthermore, the comprehensive PCA scores for organic fertilizer rates under both tillage practices consistently ranked as M2>M3>M1>M0.

Vertical deep rotary tillage combined with organic fertilizer at 1.50×10⁴ kg·hm^-2 (DT+M2) effectively enhanced LAI and LAD in maize grown on saline-alkali soil, optimized its photosynthetic and fluorescence characteristics, and significantly improved dry matter accumulation and translocation traits, thereby promoting crop yield. This treatment was recommended as a saline-alkali soil improvement measure for the Ningxia Yellow River Irrigation District.