Pig production in the State of Santa Catarina, Brazil, is responsible for many jobs in the rural area and it has great social and economic importance. This study was carried out from March to September 2012 to evaluate the influence of a single application of pig slurry to an Ultisol (Nitossolo Bruno aluminoférrico húmico) soil on losses of water, soil, P and K due to water erosion. Treatments consisted of application rates of 0 (zero), 50, 100, and 200 m³ ha-1 applied on the soil surface in a single application, which occurred 30 days after black oat germination. The plots were 11 × 3.5 m with a mean slope of 0.14 m m-1. During the oat crop cycle, four simulated rainfall tests were carried out, each one with four rainfalls with planned intensity of 65 mm h-1 and duration of 75 min, using a Swanson type rainfall simulator. The total soil and water losses by water erosion are not influenced by the pig slurry rates applied on the soil cultivated with black oat. However, there was an influence from the moisture content in the soil before the application of simulated rainfall. The soluble P and K contents in the runoff water decrease after the application of pig slurry on the soil cultivated with oat for a certain period. When the crop is subjected to simulated rain, the contents decrease from the rain of test 1 to the rain of test 3, and increase in the rain of test 4. The soluble P and K contents in the runoff water decrease from the pig slurry application rate of 100 m³ ha-1 to the control treatment (with no pig slurry application) in the simulated rainfall tests 1 and 2. The total losses of soluble P and K in the runoff water are not influenced by the pig slurry rates applied on the soil in cultivation of oat; however, they decrease from the rain of test 1 to test 3 and increase in test 4. The soluble P and K contents in the runoff water decrease with the increased number of simulated rainfall tests in soil cultivated with oat. The data fit the exponential model y = y0 + a e-bx; except for the data on K results with no pig slurry application (rate of zero m³ ha-1).
water and soil losses; phosphorus and potassium losses; pig production
