Abstract Grain legumes are known for their benefits to deliver ecosystem services on provisioning of protein-rich food and feed, reducing greenhouse gas emissions through the symbiotic nitrogen fixation function and diversification of cropping systems. Intercropping is an agroecological practice in which two or more crop species are grown simultaneously in the same field, thereby maximizing the use of resources to enhance yields in low input systems and the resilience of cropping systems. We quantified the effect of grain legume-cereal intercropping on the use of N resources in temperate agroecosystems, focusing on dinitrogen (N2) fixation and soil-derived nitrogen acquisition using a meta-analysis of 29 field-scale studies. We estimated and compared effects of different intercrop compositions (proportion of each species in the intercrops), fertilization rates, crop species, soil properties, and other management practices on the symbiotic N2 fixation and the acquisition of soil-derived nitrogen by the cereals and grain legumes. The proportion of N derived from N2 fixation was on average 14 % (95 % CI = [11, 16]) higher in intercropped grain legumes (76 %) compared to legume sole crops (66 %). On the other hand, intercropping reduced the amount of N2 fixed (kg ha−1) by about 15 %, when N2 fixation in inter- and sole cropped legumes was expressed at equivalent density by compensating for the sown legume proportion in intercrops relative to their sole crop sowing rate. The results were mainly influenced by the intercrop composition, legumes species and the method used to quantify N2 fixation. Soil-derived nitrogen acquisition in intercropped grain legumes was significantly reduced (−47 %, 95 % CI = [−56, −36]) compared to sole crop legumes, expressed at equivalent density, while the soil N acquired by intercropped cereals was much higher (+61 %, 95 % CI = [24, 108]) than in sole crop cereals. Total soil N acquisition (legume + cereal) was significantly higher in intercrops than in legume sole crops (+25 %, 95 % CI = [1, 54]), while there was no significant difference between intercrops and cereal sole crops. The meta-analysis confirms and highlights that intercropping consistently stimulates complementary N use between legumes and cereals by increasing N2 fixation by grain legumes and increasing soil N acquisition in cereals. Based on the results of this analysis it would be suggested that cropping systems diversification via intercropping can be used for simultaneous production of both cereals and grain legumes, while increasing the use of N-sources and reducing external inputs of N fertilizers, thereby enhancing the sustainability of agriculture.

中文翻译：

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谷物豆类 - 谷物间作增强了土壤来源和生物固定氮在温带农业生态系统中的使用。荟萃分析

摘要 谷物豆类以其在提供富含蛋白质的食物和饲料、通过共生固氮功能和种植系统多样化减少温室气体排放方面提供生态系统服务的益处而闻名。间作是一种农业生态实践，其中在同一土地上同时种植两种或多种作物，从而最大限度地利用资源，以提高低投入系统的产量和种植系统的复原力。我们通过对 29 项田间规模研究的荟萃分析，量化了豆类-谷物间作对温带农业生态系统中氮资源利用的影响，重点是二氮 (N2) 固定和土壤来源的氮获取。我们估计并比较了不同间作组合的影响（间作中每个物种的比例），施肥率、作物种类、土壤特性和其他关于共生固氮和谷物和谷物豆类获取土壤来源的氮的管理实践。间作谷物豆类作物 (76 %) 中源自 N2 固定的 N 比例平均比单一豆科作物 (66%) 高 14%（95% CI = [11, 16]）。另一方面，间作使固定 N2 的量（kg ha-1）减少了约 15%，当间作和单作豆科植物中的 N2 固定以相等的密度表示时，通过补偿间作中豆科植物的播种比例相对于它们的单一作物播种率。结果主要受间作组成、豆科植物种类和用于量化 N2 固定的方法的影响。与单一作物豆类相比，间作谷物豆类中土壤来源的氮获取显着减少（-47 %, 95 % CI = [-56, -36]），以等效密度表示，而间作谷物获得的土壤氮含量则更多比单一作物谷物更高（+61 %, 95 % CI = [24, 108]）。间作的土壤总氮获取（豆类 + 谷类）显着高于豆类单一作物（+25 %，95 % CI = [1, 54]），而间作和谷类单一作物之间没有显着差异。荟萃分析证实并强调，间作通过增加谷物豆类对 N2 的固定和增加谷物中土壤氮的获取，持续刺激豆类和谷物之间补充氮的使用。