The silvopastoral system avoids the degradation of tropical grasslands by providing essential nutrients to the soil while improving livestock diet and farmer's income by increasing the marketable wood supply. We hypothesize that intercropping shrub‐tree legumes into signalgrass increases microbial activity and soil organic matter (SOM) quality. We investigated silvopastoral system soils over 5 yr in a subhumid climate in northeastern Brazil to determine the total C and N contents and to estimate C‐microbial biomass and respiration, microbial and metabolic quotients, humic acid (HA), and fulvic acid (FA). The experimental design evaluated (a) signalgrass intercropped with gliricidia at 0, 4, and 8 m from the center of the double legume row; (b) signalgrass intercropped with sabia at 0, 4, and 8 m from the center of the double legume row; and (c) single signalgrass. Samples were obtained after 2, 3, 4, and 5 yr from silvopastoral system implementation. The shrub‐tree legumes soils had total C (39 g kg⁻¹) and total N (3.8 g kg⁻¹) contents significantly higher (30 and 72%, respectively) than single signalgrass soil only on the fifth year after establishment. Microbial biomass C at 0 and 4 m from the legume's rows was 700 mg kg⁻¹, which was 75% higher than single signalgrass soils. There was strong microbial respiration (∼50 mg C‐CO₂ kg⁻¹ d⁻¹) in legumes soils, but the metabolic quotient did not indicate disturbance in microbial activity. The microbial quotients were significantly higher in shrub‐tree legumes soil, and the HA/FA ratio was nearly 1, demonstrating greater efficiency in SOM decomposition by microbial activity. Overall, 5 yr after establishment, the silvopastoral system has improved SOM quality and contributed to grassland sustainability.

中文翻译：

---

豆科植物牧草系统在半湿热带环境中提高了土壤有机质的质量

牧草系统通过向土壤提供必需的养分，避免了热带草原的退化，同时通过增加可销售的木材供应来改善牲畜饮食和农民的收入。我们假设将灌木豆科植物间作到草丛中会增加微生物活性和土壤有机质（SOM）的质量。我们调查了巴西东北部半湿润气候下5年以上的牧牧系统土壤，以确定总C和N含量，并估计C微生物的生物量和呼吸，微生物和代谢商，腐殖酸（HA）和黄腐酸（FA） 。实验设计评估（a）在双豆科排中心0、4和8 m处，草皮与草皮间作；（b）在双豆科行的中心0、4和8 m处，杂草与杂草间作；（c）单信号草。在2年，3年，4年和5年后，从silvopastoral系统实施中获取样本。灌木豆科植物土壤的总碳（39 g千克^-1）和总氮（3.8 g kg ^-1）的含量仅在建立后的第五年才显着高于单信号草土壤（分别为30％和72％）。豆科植物行0和4 m处的微生物生物量碳为700 mg kg ^-1，比单一信号草土壤高75％。强烈的微生物呼吸作用（〜50 mg C-CO ₂ kg ^-1 d ^-1）在豆类土壤中，但代谢商并未表明微生物活性受到干扰。灌木豆科植物土壤中的微生物商要高得多，HA / FA比值接近1，这表明通过微生物活性进行SOM分解的效率更高。总体而言，林牧系统在建立之后的5年内提高了SOM的质量，并为草地的可持续发展做出了贡献。