Effects of different nitrogen application rates on yield and water use efficiency of silage maize

This research was conducted to investigate the effects of different nitrogen application rates on the dry matter accumulation and allocation, soil water storage, water consumption, and water use efficiency of silage maize (Yu silage 23) in the Longdong Loess Plateau in 2019 and 2020. Five nitrogen application rates, i.e., 0, 70, 140, 210, and 280 kg·ha⁻¹ (designated as N₀, N₇₀, N₁₄₀, N₂₁₀, and N₂₈₀, respectively), were used. The results indicated that dry matter accumulation tended to increase as the nitrogen application rate increased. The yield of silage maize at the milking stage was the highest in the N₂₁₀ treatment, i.e., 22.0 t·ha⁻¹ in 2019 and 23.2 t·ha⁻¹ in 2020. With the development of the growth stage, the proportion of leaf dry matter decreased, the proportion of stem dry matter increased at first and then decreased, and the proportion of ear dry matter increased gradually. As the nitrogen application rate increased, the water consumption of silage maize increased at first and then decreased. The water use efficiency in the N₂₁₀ treatment was the highest, i.e., 45.7 kg·(ha·mm)⁻¹ in 2019 and 65.0 kg·(ha·mm)⁻¹ in 2020. In conclusion, in consideration of dry matter accumulation and water use efficiency, the N application rate of 210 kg·ha⁻¹ is recommended for silage maize production in the Longdong Loess Plateau.