The Regulatory Effect of Reduced Irrigation and Combined Organic-Inorganic Fertilizer Application on Stay-Green Characteristics in Silage Maize Leaves After Tasseling Stage

The study investigated the regulatory effects of reduced irrigation and the combined application of organic and inorganic fertilizers on stay-green characteristics in leaves and yield performance of silage maize after tasseling stage, in order to explore the optimal nitrogen application ratio of organic and inorganic fertilizers under reduced irrigation conditions, so as to provide a theoretical basis for high-yield and efficient cultivation practices of silage maize in arid irrigation areas.

From 2021 to 2023, a two-factor split-plot experimental design was employed in the Hexi oasis irrigation area. The main plots consisted of two irrigation levels: reduced 20% irrigation (I1) and conventional irrigation (I2), while the subplots included five ratios of organic and inorganic fertilizer nitrogen fertilization maintaining equivalent nitrogen levels: 100% inorganic nitrogen fertilizer (F1), 75% inorganic nitrogen fertilizer+25% organic fertilizer (F2), 50% inorganic nitrogen fertilizer+50% organic fertilizer (F3), 25% inorganic nitrogen fertilizer+75% organic fertilizer (F4), and 100% organic fertilizer (F5). The study explored the response of stay-green characteristics in silage maize leaves after tasseling stage and fresh and hay yields to different irrigation amounts and organic-inorganic nitrogen fertilizer ratios.

The reduction in irrigation alone resulted in a decrease in leaf stay-green characteristics of silage maize after tasseling stage. However, combining reduced irrigation with the application of both organic and inorganic fertilizers enhanced leaf stay-green characteristics after tasseling stage. Among these combinations, the reduced 20% irrigation combined with 75% inorganic nitrogen fertilizer+25% organic fertilizer (I1F2) showed a significant advantage. I1F2 could increase leaf area index and stay-green in leaves of silage maize after tasseling. Compared with conventional irrigation combined with 100% inorganic nitrogen fertilizer (I2F1), I1F2 could increase leaf area index and stay-green in leaves by 14.3% and 6.8%, respectively. Compared with the I2F1 treatment, I1F2 also increased chlorophyll a and b content in leaves of silage maize by 14.2% and 10.7%, respectively. As the increase in chlorophyll a content was greater than that of chlorophyll b, a higher chlorophyll a/b ratio was achieved. 75% inorganic nitrogen fertilizer+25% organic fertilizer under conditions of 20% reduced irrigation enhanced the reactive oxygen species scavenging capacity in leaves of silage maize after tasseling stage. Superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase activities under I1F2 were increased by 12.0%, 7.8%, 10.7%, and 10.2% than that under I2F1, respectively. Compared with the I2F1 treatment, I1F2 increased proline and solute protein content in silage maize after tasseling stage by 9.8% and 9.7%, respectively, and reduced malondialdehyde content by 8.4%. Therefore, the silage maize under I1F2 could achieve higher fresh and hay yields at the optimal harvest time, increasing by 9.9% and 13.6% compared with I2F1. Comprehensive analysis indicated that I1F2 could significantly improve leaf area index, stay-green characteristics, and chlorophyll content of silage maize by enhancing leaf antioxidant enzyme activity, increasing content of cellular osmotic regulatory substances, and reducing malondialdehyde content after tasseling stage. Consequently, this effectively boosted the yield of silage maize.

Reduced 20% irrigation combined with 75% inorganic nitrogen fertilizer+25% organic fertilizer was an optimal water and nitrogen management strategy for extending the stay-green period of silage maize leaves after tasseling stage and increasing yield in arid irrigation areas.