Effect of nitrogen application on grass productivity and energy use efficiency in a mixed forage sorghum/lablab planting

doi:10.11686/cyxb2025059

Abstract

Abstract:

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.

Key words: seed mixing, nitrogen fertilizer, production performance, eco-efficiency index, economic benefit

Yi-yin ZHANG, Ai-ping XIAO, Bin WANG, Teng-fei WANG, Hai-ying HU, Jian LAN. Effect of nitrogen application on grass productivity and energy use efficiency in a mixed forage sorghum/lablab planting[J]. Acta Prataculturae Sinica, 2026, 35(1): 40-52.

Figures/Tables 10

References 34

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种植模式 Cropping patterns	施氮水平 Nitrogen application levels	投入成本Input cost （yuan·hm^-2）
种植模式 Cropping patterns	施氮水平 Nitrogen application levels	人工 Labor	拖拉机 Tractor	肥料 Fertilizer	农药 Pesticide	滴灌带 Drip irrigation tape	电费 Electricity bill	种子 Seed	总计 Total
SS	N₀	2313.36	1985.04	858.00	909.36	750.24	251.28	720.00	7787.28
	N₉₀	2313.36	1985.04	1344.24	909.36	750.24	251.28	720.00	8273.52
	N₁₈₀	2313.36	1985.04	1830.48	909.36	750.24	251.28	720.00	8759.76
	N₂₇₀	2313.36	1985.04	2316.72	909.36	750.24	251.28	720.00	9246.00
SL	N₀	2431.44	2309.76	858.00	763.92	750.24	243.36	2947.68	10304.40
	N₉₀	2431.44	2309.76	1344.24	763.92	750.24	243.36	2947.68	10790.64
	N₁₈₀	2431.44	2309.76	1830.48	763.92	750.24	243.36	2947.68	11276.88
	N₂₇₀	2431.44	2309.76	2316.72	763.92	750.24	243.36	2947.68	11763.12

种植模式 Cropping patterns	施氮水平 Nitrogen application levels	投入成本Input cost （yuan·hm^-2）
种植模式 Cropping patterns	施氮水平 Nitrogen application levels	人工 Labor	拖拉机 Tractor	肥料 Fertilizer	农药 Pesticide	滴灌带 Drip irrigation tape	电费 Electricity bill	种子 Seed	总计 Total
SS	N₀	2313.36	1985.04	858.00	909.36	750.24	251.28	720.00	7787.28
	N₉₀	2313.36	1985.04	1344.24	909.36	750.24	251.28	720.00	8273.52
	N₁₈₀	2313.36	1985.04	1830.48	909.36	750.24	251.28	720.00	8759.76
	N₂₇₀	2313.36	1985.04	2316.72	909.36	750.24	251.28	720.00	9246.00
SL	N₀	2431.44	2309.76	858.00	763.92	750.24	243.36	2947.68	10304.40
	N₉₀	2431.44	2309.76	1344.24	763.92	750.24	243.36	2947.68	10790.64
	N₁₈₀	2431.44	2309.76	1830.48	763.92	750.24	243.36	2947.68	11276.88
	N₂₇₀	2431.44	2309.76	2316.72	763.92	750.24	243.36	2947.68	11763.12

投入来源 Input source	SS （MJ·hm^-2）				SL （MJ·hm^-2）				能量当量系数 Energy equivalent coefficient	参考文献 References
投入来源 Input source	N₀	N₉₀	N₁₈₀	N₂₇₀	N₀	N₉₀	N₁₈₀	N₂₇₀	能量当量系数 Energy equivalent coefficient	参考文献 References
人工Human labor	192.8	192.8	192.8	192.8	202.6	202.6	202.6	202.6	1.96 MJ·h^-1	［21］
燃料Fuels	90.0	90.0	90.0	90.0	95.4	95.4	95.4	95.4	56.31 MJ·L^-1	［21］
机械Farm machinery	37.5	37.5	37.5	37.5	45.0	45.0	45.0	45.0	332 MJ·h^-1	［21］
氮肥Chemical fertilizer-N	0	90	180	270	0	90	180	270	60.6 MJ·kg^-1	［21］
磷肥Chemical fertilizer-P₂O₅	150	150	150	150	150	150	150	150	11.1 MJ·kg^-1	［21］
钾肥Chemical fertilizer-K₂O	90	90	90	90	90	90	90	90	6.7 MJ·kg^-1	［21］
农药Pesticide	0.75	0.75	0.75	0.75	0.63	0.63	0.63	0.63	120 MJ·kg^-1	［21］
滴灌带Drip irrigation belt	75	75	75	75	75	75	75	75	76 MJ·kg^-1	［21］
电费Electricity bill	838	838	838	838	812	812	812	812	11.93 MJ·Wh^-1	［21］
高粱种子Forage sorghum seed	18	18	18	18	18	18	18	18	43.5 MJ·kg^-1	［22］
拉巴豆种子Lablab seed	0	0	0	0	49.5	49.5	49.5	49.5	23.8 MJ·kg^-1	［22］

投入来源 Input source	SS （MJ·hm^-2）				SL （MJ·hm^-2）				能量当量系数 Energy equivalent coefficient	参考文献 References
投入来源 Input source	N₀	N₉₀	N₁₈₀	N₂₇₀	N₀	N₉₀	N₁₈₀	N₂₇₀	能量当量系数 Energy equivalent coefficient	参考文献 References
人工Human labor	192.8	192.8	192.8	192.8	202.6	202.6	202.6	202.6	1.96 MJ·h^-1	［21］
燃料Fuels	90.0	90.0	90.0	90.0	95.4	95.4	95.4	95.4	56.31 MJ·L^-1	［21］
机械Farm machinery	37.5	37.5	37.5	37.5	45.0	45.0	45.0	45.0	332 MJ·h^-1	［21］
氮肥Chemical fertilizer-N	0	90	180	270	0	90	180	270	60.6 MJ·kg^-1	［21］
磷肥Chemical fertilizer-P₂O₅	150	150	150	150	150	150	150	150	11.1 MJ·kg^-1	［21］
钾肥Chemical fertilizer-K₂O	90	90	90	90	90	90	90	90	6.7 MJ·kg^-1	［21］
农药Pesticide	0.75	0.75	0.75	0.75	0.63	0.63	0.63	0.63	120 MJ·kg^-1	［21］
滴灌带Drip irrigation belt	75	75	75	75	75	75	75	75	76 MJ·kg^-1	［21］
电费Electricity bill	838	838	838	838	812	812	812	812	11.93 MJ·Wh^-1	［21］
高粱种子Forage sorghum seed	18	18	18	18	18	18	18	18	43.5 MJ·kg^-1	［22］
拉巴豆种子Lablab seed	0	0	0	0	49.5	49.5	49.5	49.5	23.8 MJ·kg^-1	［22］