Farm systems, soil chemical properties, and clay dispersion in watershed áreas

Abstract: The objective of this work was to evaluate the effect of different farm systems on clay dispersion and its relationship with soil chemical properties and the no-tillage system participatory quality index (IQP), in watershed areas in the west of the state of Paraná, Brazil. The farm systems evaluated were: no-tillage; no-tillage with crop succession; no-tillage with soil disturbance; and conventional system. In addition, the farm systems were evaluated for their IQP. Soil samples were collected at 0.0-0.20-m soil depth, in 40 agricultural areas and in 6 native forests considered as references. The degree of clay dispersion, total organic carbon, pH (CaCl2), exchangeable potassium (K+), available phosphorus (P), exchangeable calcium and magnesium (Ca2++Mg2+), and potential acidity (H+Al3+) were determined. A linear multiple regression model was fitted by the method of least squares. The averages of clay dispersion degree per watershed were compared at 5% probability. The farm systems were compared by Scott-Knott’s test. Soil chemical properties showed a higher influence on clay dispersion than the different farm systems assessed. The no-tillage system alone showed the highest content of organic carbon, which was similar to those of the native areas. The conventional system and the no-tillage system with soil disturbance showed a lower IQP and a higher degree of clay dispersion than the areas with the no-tillage system alone. The IQP allows distinguishing the conventional system from the no-tillage system.摘要：本研究旨在评估巴西巴拉那州西部流域区域内，不同农作系统对黏土分散度的影响，及其与土壤化学性质、免耕系统参与式质量指数（Participatory Quality Index，IQP）的关联。受试农作系统包括纯免耕系统、作物连作免耕系统、带土壤扰动的免耕系统以及传统耕作系统；此外还对各农作系统的参与式质量指数进行了评估。于0.0~0.20米土层深度采集40个农业区域及6个作为参照的原生林样地的土壤样品，测定指标包括黏土分散度、总有机碳、氯化钙浸提pH值（pH(CaCl₂)）、交换性钾离子（K⁺）、有效磷（P）、交换性钙镁离子（Ca²⁺+Mg²⁺）以及潜在酸度（H⁺+Al³⁺）。采用最小二乘法构建线性多元回归模型，以5%显著性水平对各流域的黏土分散度平均值进行多重比较，并通过Scott-Knott检验对不同农作系统开展组间比较。结果表明，相较于受试的各类农作系统，土壤化学性质对黏土分散度的影响更为显著；纯免耕系统的总有机碳含量最高，与作为参照的原生林区域相当；传统耕作系统与带土壤扰动的免耕系统的参与式质量指数更低，且黏土分散度高于纯免耕系统区域；参与式质量指数可有效区分传统耕作系统与免耕系统。