The synergism of grass-legume consortium in silvopastoral systems has a substantial contribution to improving soil organic matter, and N and C stocks compared to pastures under grass monocropping systems. This study hypothesizes that adding legume trees into long-term established pastures has little impact on soil stability, while can potentially increase soil C and N stocks. Three systems were compared during a three-year trial (2020–2023): long-term grass pasture (Urochloa decumbens Stapf.), and successional vegetation of legume trees monocrop (Mimosa caesalpiniifolia Benth.), and silvopasture combining both species. The trial was established in a complete randomized block design with three repetitions, in an area of 7.8 ha. The type of the system did not affect soil density (p = 0.3530, 0.3986), carbon (p = 0.4771, 0.7464), nitrogen (p = 0.3904, 0.9321) stocks in the 0–10 cm and 10–20 cm layers, respectively. In the 20–40 cm layer, the soils under legume monocropping displayed higher concentrations (1.20 g kg−1; p = 0.0134) and stocks (3.00 Mg ha−1) of N compared to grass monocropping (0.84 g kg−1 and 2.22 Mg ha−1, respectively) (p = 0.0070), while the silvopastoral system showed intermediate results (1.03 g kg−1 and 2.69 Mg ha−1, respectively). There was no difference regarding C stocks among the systems, varying between 13.84 Mg ha−1 (0–10 cm layer; p = 0.4771) to 20.09 Mg ha−1 (20–40 cm layer; p = 0.9208). The different systems did not present differences in terms of soil C/N ratio (p = 0.7677, 0.1904, 0.1559), soil basal respiration (p = 0.7452, 0.7037, 0.8121), soil microbial biomass C (p = 0.1318, 0.6654, 0.8473) microbial quotient (qMIC) (p = 0.2177, 0.3670, 0.7422), metabolic quotient (qCO2) (p = 0.4142, 0.3902; 0.7297) and light fraction of organic matter (p = 0.5036, 0.4969, 0.5611), in the 0–10, 10–20 and 20–40 cm layers, respectively. The results of this study suggest that incorporating legume trees in long-term established grass pastures (20 years) does not disrupt soil qMIC and qCO2, while potentially increasing nitrogen content and stocks in deeper layers of the soil. Encouraging the implementation of silvopasture systems in well-established monocropping pastures can be considered a sustainable practice with no considerable soil disturbance.

中文翻译：

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已建立的热带草牧场中的豆科植物增加了深层土壤氮的储量


与草单一种植系统下的牧场相比，草豆类联盟在林牧系统中的作用对改善土壤有机质以及 N 和 C 储量做出了重大贡献。本研究假设将豆科植物添加到长期建立的牧场中对土壤稳定性影响不大，但可能会增加土壤 C 和 N 的储量。在一项为期三年的试验（2020-2023 年）中，比较了三个系统：长期草牧场 （Urochloa decumbens Stapf.） 和豆科植物单一作物 （Mimosa caesalpiniifolia Benth.） 的演替植被，以及结合这两个物种的林牧场。该试验采用完全随机区组设计，重复 3 次，面积为 7.8 公顷。该系统的类型分别影响 0-10 cm 和 10-20 cm 层的土壤密度 （p = 0.3530， 0.3986）、碳 （p = 0.4771， 0.7464）、氮 （p = 0.3904， 0.9321） 库存。在 20-40 cm 层中，豆科植物单一种植土壤显示出更高的氮浓度（1.20 g kg-1;p = 0.0134）和储存量（3.00 Mg ha-1），与草单一种植相比（分别为 0.84 g kg-1 和 2.22 Mg ha-1）（p = 0.0070），而林牧系统显示出中等结果（分别为 1.03 g kg-1 和 2.69 Mg ha-1）。不同系统的碳储量没有差异，在 13.84 Mg ha-1（0-10 cm 层;p = 0.4771）到 20.09 Mg ha-1（20-40 cm 层;p = 0.9208）之间变化。不同系统在土壤 C/N 比 （p = 0.7677， 0.1904， 0.1559）、土壤基础呼吸 （p = 0.7452， 0.7037， 0.8121）、土壤微生物量 C （p = 0.1318， 0.6654， 0.8473） 微生物商 （qMIC） （p = 0.2177， 0.3670， 0.7422）、代谢商 （qCO2） （p = 0.4142， 0.3902;0.7297） 和有机物的轻分数 （p = 0.5036， 0.4969， 0.5611），分别在 0-10、10-20 和 20-40 cm 层中。这项研究的结果表明，在长期建立的草牧场（20 年）中种植豆科植物不会破坏土壤 qMIC 和 qCO2，同时可能会增加土壤深层的氮含量和储量。鼓励在成熟的单一作物牧场中实施林牧系统可以被认为是一种可持续的做法，不会对土壤造成相当大的干扰。