Water erosion of dystrophic Red Latosols (Oxisols)

ABSTRACT In their natural state, Latosols (Oxisols) present great stability and resistance to erosion, being the most abundant and used soils for farming and cattle raising activities in southern Minas Gerais State, Brazil. However, along the last one hundred years, they have been submitted to intensive cultivation and managements which favor water erosion. This study aimed to estimate the water erosion rates of dystrophic Red Latosols from the Revised Universal Soil Loss Equation, compared with the soil loss tolerance limits, and assess the impact on water erosion of the managements more common in the region, by alternative conservation management simulation. Soil loss tolerance limits ranged from 8.94 Mg ha-1 year-1 to 9.99 Mg ha-1 year-1, with the study area presenting a susceptibility of soil loss of 23.86 Mg year-1, with an average rate of 8.40 Mg ha-1 year-1, corresponding to 34.80 % of the area with values above the soil loss tolerance limit. The biggest annual losses occur in areas with use and management of eucalyptus grown downhill (30.67 Mg ha-1 year-1) and pasture under continuous occupancy (11.10 Mg ha-1 year-1). However, when the average loss per type of use is considered, the areas more susceptible to water erosion are those with potato and eucalyptus crops, grown downhill, and those in bare soil. Nevertheless, in the simulated conservation management scenario, the average losses would be drastically reduced (8.40 Mg ha-1 year-1 to 2.84 Mg ha-1 year-1) and only 4.00 % of the area with soil loss would remain above the tolerance limits.

摘要
铁铝土（Latosols，亦称Oxisols）在自然状态下具备极强的稳定性与抗侵蚀能力，是巴西米纳斯吉拉斯州南部分布最广、应用于农业种植与畜牧养殖的核心土壤类型。然而在过去百年间，这类土壤历经高强度耕作与不合理的管理措施，大幅加剧了水蚀发生风险。
本研究旨在借助修正通用土壤流失方程（Revised Universal Soil Loss Equation），估算瘠薄红色铁铝土的水蚀速率并与土壤允许流失量阈值进行对比；同时通过模拟不同保护性管理模式，评估该区域主流土地管理措施对水蚀过程的影响。
研究区域的土壤允许流失量阈值介于8.94 吨·公顷⁻¹·年⁻¹至9.99 吨·公顷⁻¹·年⁻¹之间；该区域土壤流失敏感性均值为23.86 吨·年⁻¹，平均水蚀速率为8.40 吨·公顷⁻¹·年⁻¹，其中34.80%的区域土壤流失量超出允许阈值。
年度土壤流失量最高的区域为顺坡种植桉树的地块（30.67 吨·公顷⁻¹·年⁻¹）与长期连续放牧的草地（11.10 吨·公顷⁻¹·年⁻¹）。但若按不同土地利用类型的平均流失量来看，水蚀敏感性最高的区域则为顺坡种植马铃薯与桉树的地块，以及裸地区域。
不过在模拟采用保护性管理模式的情景下，区域平均土壤流失量将从原有的8.40 吨·公顷⁻¹·年⁻¹大幅降至2.84 吨·公顷⁻¹·年⁻¹，仅剩余4.00%的区域土壤流失量超出允许阈值。