Abstract:

To optimize the N and P dosing scheme for corn-soybean composite planting, this study employed a mixed planting of corn and soybean using saline-alkali soil as the growing medium, including four nitrogen levels (0, 270, 300, 330 kg/hm², designated as N0, N1, N2, N3) and four phosphorus levels (0, 60, 90, 120 kg/hm², designated as P0, P1, P2, P3). Soil nutrients, soil enzyme activities, and physiological activities of corn and soybean leaves and roots were measured after 60 days. The results showed that P2 and P3 increased soil alkaline dissolved nitrogen (7.81%-48.99%) and effective phosphorus content (21.33-fold increase) and soil enzyme activities at different N application levels; N2 and N3 increased soil alkaline dissolved nitrogen (19.57%-48.99%) and effective phosphorus content (9.81-fold increase) at different phosphorus application levels; and N3P2 increased soil sucrase (32.36%) and alkaline phosphatase (29.89%) activities, N3P2 increased soybean root POD activity, decreased root MDA content, and increased leaf SOD activity; and N1P1 and N2P1 increased maize root POD activity, decreased leaf and root MDA content, and increased leaf and root SOD activity. The high nitrogen and high phosphorus pairing increased soil alkaline dissolved nitrogen and effective phosphorus content, and high nitrogen or phosphorus increased soil sucrase and alkaline phosphatase activities, while the low nitrogen and high phosphorus pairing increased soil cellulase activity; N₃P₂ enhanced the quality of corn-soybean mixed planting soils, and strengthened the physiological activity of crop seedlings.

Key words: nitrogen and phosphorus interactive application, corn-soybean mixed planting, soil nutrients, physiological characteristics of plants, soil enzyme