Soil and water loss and quality of surface runoff associated with interrill erosion in no-tillage area treated with chemical and organic fertilizers

Among conservation tillage methods, no-till has shown to be the most effective in reducing soil losses caused by rainfall erosion, but with considerable data variation regarding water loss. Considering these aspects, this study was carried out with the objective of evaluating soil and water losses, the chemical demand of oxygen (CDO), electrical conductivity, and the pH of surface runoff, associated with interrill erosion under simulated rainfall. The field study was conducted in October 2003 in Marechal Candido Rondon county, western Parana state, Brazil, in an area cultivated under no-till and that received chemical and organic fertilization. The soil is a clayey Oxisol (eutroferric Red Latosol) with 0.045 m m(-1) slope. On small plots (1.0 x 1.0 m) with pre-wetted soil, the following rainfall intensities were applied by a rotating-boom rainfall simulator: 70.0, 60.0 and 120.0 mm h(-1), during 20 min each, with time intervals of 30 min in-between. The treatments consisted of (a) chemical fertilization, with nitrogen, phosphorous, and potassium -NPK, (b) organic fertilization with liquid swine manure-DLS, and (c) no-fertilization (control treatment) T. The highest soil and water losses in the experiment were observed in the DLS treatment, regardless of the simulated rains (except soil loss in the last rain, which reached the highest value in the study); the results of NPK and control T treatments were similar. The highest values of chemical oxygen demand, electrical conductivity and pH of surface runoff were also observed in the DLS treatment, while the lowest values occurred in the T treatment (except the chemical oxygen demand in the NPK treatment, which was also low), regardless of the simulated rains.