Water Erosion in a Long-Term Soil Management Experiment with a Humic Cambisol

ABSTRACT Water erosion, the main factor in soil degradation, is strongly influenced by soil cover and management. The objective of this study was to determine soil and water losses under natural rainfall conditions from 1993 to 2012 in the southern Santa Catarina Plateau, Brazil, in 3.5 × 22.1 m plots with crops in rotation to study the following management treatments: conventional tillage (CT), minimum tillage (MT), and no-tillage (NT), and a treatment with bare soil (BS). The soil cover remaining after tillage was negatively affected by the increase in soil tillage intensity. Soil losses were strongly affected by the management system, while water losses were less affected. Soil losses were 85.29, 6.41, 2.00, and 0.82 Mg ha-1 yr-1 in the BS, CT, MT, and NT treatments, respectively, while water losses were 38, 24, 15, and 9 % of the rainfall, respectively, in the annual mean. Soil losses in spring/summer were similar to those of autumn/winter in the CT, MT, and NT treatments, while water losses were influenced by the time of year in all soil management systems. The accumulated soil losses in the MT and NT treatments tended to stabilize over the period evaluated, whereas they increased an average of 88.12 Mg ha-1 yr-1 in the BS and 7.23 Mg ha-1 yr-1 in the CT treatments. The accumulated water losses had a linear response, with positive angular coefficients for all treatments. The relationship between annual soil and water loss data was significant in the BS treatment; in the CT, MT, and NT treatments, this relation was not significant.

摘要：水蚀是引发土壤退化的核心因素，其发生过程深受土壤覆盖状况与耕作管理措施的影响。本研究以巴西圣卡塔琳娜高原南部为研究区域，于1993年至2012年的自然降雨条件下开展水土流失监测试验，试验采用规格为3.5×22.1 m的径流小区，种植轮作作物，设置4组耕作管理处理：常规耕作（conventional tillage, CT）、少耕（minimum tillage, MT）、免耕（no-tillage, NT）以及裸地（bare soil, BS）。
耕作后留存的土壤覆盖度随土壤耕作强度的提升而显著降低。土壤侵蚀量受耕作管理系统的影响极为显著，而径流水量损失受其影响相对较弱。裸地、常规耕作、少耕与免耕处理的土壤侵蚀量依次为85.29、6.41、2.00与0.82 吨·公顷⁻¹·年⁻¹；各处理的年平均径流水量损失占降雨量的比例则依次为38%、24%、15%与9%。
常规耕作、少耕与免耕处理下，春夏季与秋冬季的土壤侵蚀量无显著差异；但所有土壤管理系统中，径流水量损失均受季节时段的显著调控。少耕与免耕处理的累积土壤侵蚀量在本研究评估周期内趋于稳定；而裸地与常规耕作处理的累积土壤侵蚀量年均分别增加88.12吨·公顷⁻¹·年⁻¹与7.23吨·公顷⁻¹·年⁻¹。
各处理的累积径流水量损失均呈线性响应特征，且所有处理的回归斜率均为正值。裸地处理的年土壤侵蚀量与径流水量损失间存在显著相关关系；而常规耕作、少耕与免耕处理中，二者的相关关系并不显著。