饲用高粱/拉巴豆混播模式下施氮量对草地生产力和能量利用效率的影响OA

The aim of this study was to determine the effects of different nitrogen application rates on grassland production performance,economic efficiency,energy use efficiency,and ecological efficiency index under mixed seeding conditions.The overall aim of our research was to provide a scientific basis for the efficient use of N fertilizer to achieve environmentally sustainable development.We conducted a field trial in 2021-2023 at the Sidunzi Grass Field Science Research Base of Ningxia University.The experiment had a two-factor design with two cropping patterns(SS:forage sorghum monoculture;SL:forage sorghum/lablab mixed cropping)and four N application rates(N0:0 kg·ha-1;N90:90 kg·ha-1;N180:180 kg·ha-1;N270:270 kg·ha-1).It was found that the synergistic effect of mixed seeding and nitrogen fertilization significantly increased the hay yield and crude protein yield of the system.The optimum production performance was obtained with the mixed crop fertilized with N at 180 kg·ha-1.This treatment had the highest hay yield(29.08 t·ha-1)and crude protein yield(2.62 t·ha-1).These values were higher on average by 20.69%-23.86%and 21.03%-26.89%,respectively,compared with those in the other treatments and the control.An economic benefit analysis showed that the forage sorghum/lablab mixed planting fertilized with 180 kg·ha-1 N had the highest average annual net income and net energy output.The values for this treatment 33.94%and 21.32%higher,respectively,than those in the control(no fertilizer),demonstrating good economic-energy synergy effects.The forage sorghum/lablab mix with 90 kg·ha-1 N application had the highest energy use efficiency and energy productivity at 10.84 and 0.60 kg·MJ-1,respectively.These values were 1.94%and 1.95%higher than the respective values in the control.The sustainability of the different cropping patterns was evaluated on the basis of the forage yield,economic efficiency,energy use efficiency,and ecological efficiency index.The highest sustainability index(0.97)was obtained for the mixed crop with N application at 180 kg·ha-1.Therefore,application of N fertilizer at 180 kg·ha-1 is the optimum level for the forage sorghum/lablab mixed cropping system in the Northwest Arid Zone.This treatment improves the forage yield and sustainability of the cropping system with relatively low N fertilizer inputs.