Effects of phosphate fertilization and intercropping on plant growth, nitrogen and phosphorus uptake of millet and soybean across three soil types

Aim: In arid and semi-arid regions, soil phosphorus (P) deficiency often limits the development of agriculture. Intercropping is considered as a key mode to improve P use-efficiency in P poor soils. This study aimed to investigate the effect of P fertilization and intercropping on plant growth, nitrogen (N) and P uptake of millet and soybean across three soil types. Methods: A greenhouse pot experiment was conducted, and three factors were designed, including P supply levels (0, 30, and 150 mg kg-1), planting modes (monocultured millet, monocultured soybean, and intercropped millet-soybean), and soil types (the loess soil, Aeolian sandy soil, and mixed soil). Plant P uptake, root organic acid contents and phosphatase activity were used to characterize the P-utilization potential of plants. Key results: Both P supply and intercropping increased plant dry mass, but no significant interaction between P and planting modes was observed. Maize N and P uptake under intercropping was greater than that under monoculture in most treatments. Soybean secreted more kinds of carboxylate than millet. Both P30 and intercropping enhanced exudation of tartrate, succinate, malate, and malonate by roots. Soil alkaline phosphatase activity in the mixed soil was higher than that in the loess soil. Conclusions: Adding P and intercropping can promote plant growth, N and P uptake. Increased soil phosphatase activity and carboxylate secretion by roots were the key mechanisms for soil P mobilization. This study can provide a feasible scheme for agricultural production in arid and semi-arid areas.