Nutrient accumulation and availability and crop yields following long-term application of pig slurry in a Brazilian Cerrado soil

Long-term applications of pig slurry may change nutrient status and availability through the soil profile, especially in highly weathered Brazilian soils, which present low pH and nutrient availabilities as well as high Al contents. This study evaluated the effects of long-term applications of pig slurry on soil phosphorus, potassium, copper, manganese, and zinc at different soil depths, as follow: 0–0.10, 0.10–0.20, 0.20–0.40, 0.40–0.60, 0.60–0.90, and 0.90–1.20 m and on soybean and corn yields in a Brazilian Cerrado soil. Pig slurry was applied during 9 years, as follow: 0, 25, 50, 75, and 200 m³ ha⁻¹ year⁻¹for corn and 0, 25, 50, 75, and 100 m³ ha⁻¹ year⁻¹for soybean. An additional treatment using NPK fertilizer was also included for comparison. Phosphorus and potassium availabilities increased following pig slurry application. However, this increase for phosphorus occurred only in soil surface while potassium was distributed along the soil profile, showing that potassium is prone to be leached. Total and available zinc, copper, and manganese contents increased upon increasing the applied pig slurry rates. However, total contents remain below the maximum regulatory levels suggested for Brazilian soils. Maximum soybean yields were obtained with 88 m³ ha⁻¹ year⁻¹of pig slurry while corn required a rate of 127 m³ ha⁻¹ year⁻¹for maximum grain yield. Considering the production system with soybean and corn in the Cerrado soil, we recommend applications of low pig slurry rates combined with the use of mineral fertilizer, which is advantageous for both, agriculture and waste disposal.