Increasing pasture biomass production through nitrogen fertilization enables greater stocking rate and grazing intensification in pastoral livestock production systems. However, grazing intensification can compromise the soil physical quality if stocking rates exceed the soil bearing capacity to support treading. The objective was to quantify the impact of long-term (12 years) intensified grazing of Panicum maximum Jacq. cv. IPR-86 Milênio on the physical quality of a sandy soil (Luvisol Ferric soil) under subtropical climate. The 12-year field experiment was arranged in a completely randomized split-plot design with four replicates. The approach for moving the animals in and out of the paddocks varied across harvests. In the first five harvests, the period of use and rest was fixed with each paddock being occupied for 5 days followed by 35 days of rest (i.e., 40-day grazing cycle). In the subsequent harvests, the timing for moving animals in and out of each paddock was based on pasture height, with entry set at 0.90 m and exit at 0.40 m. Grazing intensification levels (IL) consisted of different animal stocking rates, grazing cycles, and forage biomass, which varied depending on the nitrogen application doses: 0 (IL-0), 150 (IL-150), 300 (IL-300), and 450 (IL-450) kg of N ha−1 year−1. Undisturbed soil samples were taken at four depths (0–0.10, 0.10–0.20, 0.20–0.30, and 0.30–0.40 m) in two sampling positions (under plants vs. between plants) and used to measure several soil physical properties (e.g., bulk density, macroporosity, mesoporosity, microporosity, water and air storage capacity, available water, pore size distribution, and water retention curve). The impact of grazing intensification on soil physical quality was minor, occurring only between plants and at the 0–0.10 m depth, where an increase in soil bulk density and a decrease in microporosity was observed. Grazing intensification also increased the water retention capacity between plants. Regardless of the sampling position and the grazing IL, water and air storage capacity was not detrimental to plant development. Overall, the increased animal stocking rate resulting from the greater pasture biomass production due to improved nitrogen fertilization does not degrade soil physical quality.

中文翻译：

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氮肥允许放牧集约化，而不会降低土壤物理质量


通过氮肥增加牧场生物量生产可以提高畜牧业生产系统的放养率和放牧集约化。然而，如果放牧率超过支持踩踏的土壤承载能力，放牧集约化会损害土壤物理质量。目的是量化 Panicum maximum Jacq 长期（12 年）集约化放牧的影响。简历 IPR-86 Milênio 关于亚热带气候下沙质土壤（Luvisol 铁质土壤）的物理质量。12 年田间试验采用完全随机的分裂区设计，有 4 个重复。将动物移入和移出围场的方法因收获而异。在前五次收获中，使用和休息时间是固定的，每个围场占用 5 天，然后休息 35 天（即 40 天的放牧周期）。在随后的收获中，将动物移入和移出每个围场的时间基于牧场高度，入口设置为 0.90 m，出口设置为 0.40 m。放牧集约化水平 （IL） 由不同的动物放养率、放牧周期和牧草生物量组成，它们根据施氮剂量而变化：0 （IL-0）、150 （IL-150）、300 （IL-300） 和 450 （IL-450） kg N ha-1 年-1。在两个采样位置（植物下方与植物之间）的四个深度（0-0.10、0.10-0.20、0.20-0.30 和 0.30-0.40 m）采集未受干扰的土壤样本，用于测量多种土壤物理特性（例如，容积密度、大孔隙度、中孔度、微孔隙度、水和空气储存能力、可用水、孔径分布和保水曲线）。 放牧加剧对土壤物理质量的影响很小，仅发生在植物之间和 0-0.10 m 深度，观察到土壤容重增加和微孔隙率降低。放牧集约化也增加了植物之间的保水能力。无论采样位置和放牧 IL 如何，水和空气的储存能力都不会对植物发育造成不利影响。总体而言，由于氮肥的改进，牧场生物量产量增加，导致动物放养率增加，这不会降低土壤的物理质量。