Abstract Introducing cover crops during the rotation system and off-season can provide numerous benefits to the agricultural system, such as increased carbon stock and improved soil aeration. However, in the southern Amazon region, owing to the hot and humid climate, the cover crops used in agricultural production systems may not have the same beneficial effects in the Cerrado region. This makes it necessary to introduce and study new species of cover crops that have the potential to improve soil quality. The objective of this study was to compare, over time, the dry matter production of eight cover crops, and the effects of their cultivation on the physical attributes of the soil in the southern Amazon region. The experiment was conducted in a randomized complete block design with analyzes carried out over the 3 years of the experiment, in three replicates. The treatments were composed of eight cover crops: crotalaria (Crotalaria spectabilis), pigeon pea (Cajanus cajan), velvet-bean (Mucuna aterrima), buckwheat (Fagopyrum esculentum), ruziziensis grass (Urochloa ruziziensis), brizantha grass (Urochloa brizantha), pearl millet (Pennisetum glaucum), and finger millet (Eleusine coracana), and three evaluation years (2014, 2015, and 2016). The cover crops used in the experiment were selected based on their adaptation to the growing conditions and because they have characteristics of agricultural interest. In addition, cover crops chosen can be used in soybean-maize rotation systems, soybean-maize succession systems, as well as in agriculture-livestock integration systems through integrated cultivation systems. Using undisturbed soil samples, were analyzed the physical variables: porosity, mechanical resistance to root penetration and water retention. Pore size distribution was calculated using the first derivative of the equation of van Genuchten and S index was determined by the angle of inclination of the soil water retention curve inflection point. The results show that leguminous and grassy cover crops act differently under physical soil attributes over time. The results indicated that the cultivation of grasses, such as P. glaucum, increased the values of macroporosity (0.18 m3 m−3) in the 0.00–0.10 m layer at the end of the third year of cultivation, consequently, reduced the value of soil density (up to 1.14 Mg m−3) and mechanical resistance to root penetration (up to 1.77 MPa). The largest accumulation of dry matter was obtained with the cultivation of U. brizantha, which consequently proved to be the best cultivation option in the off-season in the southern Amazon region. The study provides a better understanding of the influence of cover crops on the physical attributes of the soil, which will contribute to making the correct recommendation of cover crops that can improve the physical properties of the soil in agricultural frontier regions in the southern Amazon rainforest.

中文翻译：

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在亚马逊南部地区使用覆盖作物：对土壤物理质量有什么影响？

摘要 在轮作系统和淡季引入覆盖作物可为农业系统带来诸多好处，例如增加碳储量和改善土壤通气。然而，在亚马逊南部地区，由于气候炎热潮湿，农业生产系统中使用的覆盖作物在塞拉多地区可能没有同样的有益效果。这使得有必要引入和研究具有改善土壤质量潜力的覆盖作物新品种。本研究的目的是比较随着时间的推移，八种覆盖作物的干物质产量，以及它们的种植对亚马逊南部地区土壤物理属性的影响。该实验是在随机完整区组设计中进行的，并在 3 年的实验中进行了分析，在三个重复。处理由八种覆盖作物组成：crotalaria (Crotalaria spectabilis)、木豆 (Cajanus cajan)、绒豆 (Mucuna aterrima)、荞麦 (Fagopyrum esculentum)、ruziziensis 草 (Urochloa ruziziensis)、brizantha 草 (Urochloa brizanthloa)珍珠粟（Pennisetum glaucum）和指粟（Eleusine coracana），三个评价年（2014、2015和2016）。试验中使用的覆盖作物是根据它们对生长条件的适应性选择的，因为它们具有农业利益的特征。此外，选择的覆盖作物可用于大豆-玉米轮作系统、大豆-玉米演替系统，以及通过综合栽培系统的农牧一体化系统。使用未受干扰的土壤样品，分析了物理变量：孔隙率、对根部渗透的机械阻力和保水性。使用van Genuchten方程的一阶导数计算孔径分布，S指数由土壤保水曲线拐点的倾角确定。结果表明，随着时间的推移，豆科和禾本科覆盖作物在物理土壤属性下的作用不同。结果表明，种植青蒿等牧草，在种植第三年末提高了 0.00-0.10 m 层的大孔隙度值（0.18 m3 m-3），从而降低了土壤密度（高达 1.14 Mg m-3）和根部穿透的机械阻力（高达 1.77 MPa）。种植 U. brizantha 获得了最大的干物质积累，因此，这被证明是亚马逊南部地区淡季的最佳种植选择。该研究有助于更好地了解覆盖作物对土壤物理属性的影响，这将有助于正确推荐能够改善亚马逊热带雨林南部农业前沿地区土壤物理特性的覆盖作物。