Simulation of dry matter accumulation and nitrogen absorption in a maize/soybean intercropping system supplied with different nitrogen levels

Maize/soybean intercropping has yield advantages to an extent. However, different nitrogen supply levels have different effects on dry matter accumulation and nitrogen uptake in the maize/soybean intercropping system. A field experiment with a split design and logistic model were used to simulate dynamic changes in dry matter accumulation and nitrogen uptake in a maize/soybean intercropping system supplied with four nitrogen levels. Simulation results showed that dry matter accumulation and nitrogen uptake dynamics in maize and soybean were consistent with the logistic model, with correlation coefficients (R²) higher than 0.9 at the four nitrogen levels. The maximum growth rate (I_max-B) of intercropped maize compared with monoculture increased by 34.2%, 46.7%, 25.9% and 25.1% when the nitrogen supply levels were N0 (without N supply), N1 (180 kg·hm^-2), N2 (240 kg·hm^-2), and N3 (300 kg·hm^-2), respectively. The I_max-B of the soybean decreased by 27.7%, 30.3%, 16.5%, and 23.7%, respectively. However, the average I_max-B in the intercropping system was increased by32.1%. The other dry matter simulation parameters of maize and soybean were consistent with the I_max-B. Additionally, nitrogen uptake dynamics showed synchronous changes with dry matter accumulation. Under N1 treatment, the maximum nitrogen uptake (K_-N), maximum uptake rate (I_max-N), and instantaneous uptake rate (r_-N) of intercropped maize was 18.4%, 48.9%, and 25.8% higher than that of the monoculture, while the K_-N, I_max-N, and r_-N of the intercropped soybean was 15.9%, 29.9%, and 16.69% lower than that of the monoculture, respectively. The simulation parameters of K_-N, I_max-N, and r_-N in the intercropping system were 0.4%, 13.7%, and 7.8% higher than those of monoculture, respectively. Nitrogen supply had no significant effect on r_-N of soybean. A significant advantage of nitrogen in the intercropping system was observed with nitrogen land equivalent ration (LER_N)>1, and the LER_N value under N0 treatment was the highest. With the increase in nitrogen application, the LER_N exhibited a downward trend. In the present experiment, the highest dry matter accumulation and nitrogen uptake were observed under N2 treatment, which had obvious advantages for intercropping.