Legume-grass intercropping is proposed as a globally sustainable approach to enhance forage crop productivity and quality while supporting agropastoral ecosystem functioning. However, the mechanism involved in interspecific complementarity and competition driven forage productivity, quality, resource utilization, and economic benefits across different proportions of intercrops remains unclear, particularly under interannual climate variability. To address this, a 3-year field experiment was conducted in the agropastoral area of the Qinghai-Tibet Plateau (QTP) to assess the effects of different legume proportions (five legume-grass intercropping and their respective monocultures) and growing seasons on the productive, biological and economic viability. The results showed that legume proportions of 40 % and 50 % achieved the highest forage yield, system productivity (SP), water use efficiency (WUE), land equivalent ratio (LER), net profit (NP), return on investment (ROI), biodiversity effect (NE), and complementarity effect (CE) compared to other intercropping and monocultures (P < 0.05). As the legume proportion increased, yield stability, selection effect, crude protein (CP) and ash contents, grass aggressivity and competitive ratio significantly increased (P < 0.05), while ether extract (EE), crude fiber (CF), nitrogen-free extract (NFE), gross energy (GE), legume aggressivity and competitive ratio significantly decreased (P < 0.05). Additionally, the lowest forage yield, SP, NP, ROI, CP, EE, NFE, GE, and the highest WUE, LER, NE, CE, CF and ash contents were observed during the dry season (P < 0.05). Overall, our results suggested that the optimal legume proportions of 40–50 % increased forage productivity, land and water use efficiency, and economic benefits in intercropping system by improving complementarity and competitive trade-offs, which helps the intercropping systems better adapt to climatic droughts in the semiarid regions of the QTP.

中文翻译：

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互补和竞争性权衡提高了豆草间作的牧草生产力、营养平衡、土地和水的使用以及经济性


豆草间作被认为是一种全球可持续的方法，可以提高牧草作物的生产力和质量，同时支持农牧生态系统的运作。然而，种间互补和竞争驱动不同比例间作作物的饲料生产力、质量、资源利用和经济效益的机制仍不清楚，特别是在年际气候变率下。为了解决这个问题，在青藏高原 （QTP） 的农牧区进行了一项为期 3 年的田间试验，以评估不同豆科植物比例（五种豆科草间作及其各自的单一栽培）和生长季节对生产力、生物和经济可行性的影响。结果表明，与其他间作和单一栽培相比，40 % 和 50 % 的豆科植物比例实现了最高的牧草产量、系统生产力 （SP）、水分利用效率 （WUE）、土地等效比 （LER）、净利润 （NP）、投资回报率 （ROI）、生物多样性效应 （NE） 和互补效应 （CE） （P < 0.05）。随着豆科植物比例的增加，产量稳定性、选择效果、粗蛋白（CP）和灰分含量、草的侵略性和竞争率显著增加（P < 0.05），而醚提取物（EE）、粗纤维（CF）、无氮提取物（NFE）、总能（GE）、豆科植物侵略性和竞争率显著降低（P < 0.05）。此外，旱季牧草产量最低，SP、NP、ROI、CP、EE、NFE、GE，以及最高的 WUE、LER、NE、CE、CF 和灰分含量 （P < 0.05）。 总体而言，我们的结果表明，40-50% 的最佳豆科植物比例通过提高互补性和竞争性权衡，提高了间作系统的饲料生产力、土地和水利用效率以及经济效益，这有助于间作系统更好地适应 QTP 半干旱地区的气候干旱。