Abstract:

To reveal the effect of different nitrogen application rates on photosynthetic characteristics of different canopy layers of high-yield spring soybean under drip irrigation, under field condition, the effects of 4 nitrogen application levels (0, 75, 150 and 225 kg/hm ²) on the plant morphological characteristics, the chlorophyll content and photosynthetic parameters of different canopy leaves of high yield spring soybean were studied. The results showed that the increase of nitrogen fertilizer significantly increased the internode length, petiole length and leaf shape index of soybean plants; it also increased the chlorophyll content of different canopy leaves of soybean; the decrease of chlorophyll content in the middle and upper leaves of the plant treated with nitrogen fertilizer was 1.31%-4.44% lower than that of the N₀ treatment. The net photosynthetic rate (P_n) of different canopy leaves at different growth stages increased, which slowed down the decline of net photosynthetic rate of different canopy layers at different mid-late stages. The production of N₁₅₀ was relatively high, which was 4889.62 kg/hm ². Agronomic efficiency of nitrogen fertilizer was 3.58 kg/kg.

Key words: nitrogen fertilizer, spring soybean, canopy layers structure, photosynthetic characteristics, yield