No‐tillage farming combined with temporary cattle grazing is becoming a common practice in parts of South America. We quantified the effects of no‐tillage and winter grazing of annual ryegrass (Lolium multiflorum Lam.) on soil carbon and nitrogen stock, stratification ratio (concentration in 0–5 to 10–20‐cm layer) and lability (based on particulate organic matter, POM), relative to conventional tillage or ungrazed ryegrass. A 9‐year‐old experiment was conducted in a southern Brazilian Ferralsol. Soil under no‐tillage accumulated 1.11 Mg C ha⁻¹ year⁻¹ and 0.10 Mg N ha⁻¹ year⁻¹ to 100‐cm depth relative to conventional tillage when ryegrass was not grazed, and also increased the stratification ratio of carbon (1.48 vs. 1.11) and nitrogen (1.66 vs. 1.17). The carbon and nitrogen lability was also greater in no‐tillage soil, as carbon and nitrogen stocks increased proportionally more in sand‐POM than in silt or clay size fractions (carbon lability index = 1.57 vs. 1.00; nitrogen lability index = 1.57 vs. 1.00). Semiquinone concentrations in physical fractions were 4–28% smaller in no‐tillage, suggesting less organic matter aromaticity in this treatment. Grazing, however, caused no further improvement of stocks of carbon and nitrogen in the 0–100‐cm layer of no‐tillage soil (e.g., 209 vs. 212 Mg C ha⁻¹, ns), or enhancement of stratification or lability of those elements, relative to ungrazed ryegrass. Overall, no‐tillage effectively promoted soil carbon and nitrogen accumulation and lability in this subtropical Ferralsol, whereas grazing did not compromise the gains of no‐tillage.

中文翻译：

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免耕和黑麦草放牧对亚热带Umbric Ferralsol的种群，碳和氮的分层和不稳定性的影响

免耕农业与临时放牧相结合已成为南美部分地区的普遍做法。我们量化了一年生黑麦草（黑麦草）的免耕和冬季放牧对土壤碳和氮储量，分层率（0-5至10-20cm的浓度）和不稳定性（基于颗粒有机物）的影响。物质（POM），相对于传统耕作或未磨碎的黑麦草。在巴西南部的Ferralsol进行了9年的实验。免耕土壤累积的养分为1.11 Mg C ha - ¹年^-1和0.10 Mg N ha - ¹年^-1在不放牧黑麦草的情况下，其相对于传统耕作的深度可达100厘米，并且还增加了碳（1.48对1.11）和氮（1.66对1.17）的分层率。在免耕土壤上，碳和氮的稳定性也更高，这是因为砂-POM中的碳和氮储量成比例地增加，比淤泥或粘土粒度分数更大（碳的不稳定性指数= 1.57对1.00；氮的不稳定性指数= 1.57对1.00）。免耕中物理部分的对苯二酚浓度降低了4％至28％，这表明该处理中有机物的芳香性较低。然而，放牧并没有进一步改善免耕土壤0–100-cm层中的碳和氮储量（例如，209 vs. 212 Mg C ha ^-1，ns）或相对于未磨合的黑麦草增强这些元素的分层或不稳定性。总体而言，免耕有效地促进了该亚热带Ferralsol的土壤碳，氮积累和不稳定性，而放牧并没有损害免耕的收益。