The aim of this study was to evaluate the phosphorus (P) extraction ability of the methods Mehlich 1 (M-1), Mehlich 3 (M-3), anion exchange resin in strips (AER-ST), and anion exchange resin in spheres (AER-SP), as a function of clay content, P rates, and incubation time. Experimental units were built with 20%, 40%, 60%, and 80% of clay and five different phosphorus rates as follows: 0, 100, 200, 400, and 600 mg P kg −1 , with subsequent incubation for 0, 30, and 90 days. After that, the samples were subjected to the analysis of extractable P using the M-1, M-3, AER-ST, and AER-SP extractors. All P extraction methods evaluated were sensitive to clay content and to the amount of added P. The input of P increased the recovery of this nutrient by all extractors, but this was less effective when the clay content of the soil was increased. In general, the ability of phosphorus extraction from the soil followed the order: M-1 > AER-SP > M-3 > AER-ST. The longer contact time of P with the soil, lower is the extracted P content, regardless of the extraction method, this being more evident in clayey soils. All extraction methods tested are sensitive to clay content, incubation time, and to the P concentration applied.

A distribuição superficial no solo de dejetos líquidos de suínos (DLS) visando a fertilização das culturas é uma atividade comum nas propriedades rurais produtoras de suínos. O objetivo do trabalho foi avaliar a qualidade do solo em função da quantificação dos atributos químicos do solo em diferentes sistemas de manejo e tempo de uso de DLS. Foram avaliados atributos químicos de um Neossolo Regolítico, em três camadas. Os tratamentos foram compostos por uma área de mata nativa (MN) e três áreas de cultivo: pastagem perene de tifton 85 (Cinodon spp.) com uso sucessivo de DLS durante quatro anos (PP4) e 16 anos (PP16) e cultivo anual de grãos em plantio direto durante 16 anos (PD), localizadas em uma propriedade rural do município de Três Passos, RS. O uso de DLS em PP4 e PP16 aumentaram o teor de Cu e Zn na camada superficial do solo mostrando contribuição significativa dos DLS no aumento destes elementos no solo. A aplicação sucessiva de DLS em PP16 aumentou os teores P na camada de 0-5 cm acima do limite crítico ambiental (LCA-P), podendo comprometer a qualidade do solo. A capacidade de troca de cátions (CTC), carbono orgânico total (COT) e os teores de Cu, Zn e P no solo são os atributos químicos que podem ser usados como indicadores de qualidade do solo.

There is a need to evaluate the interference of pig slurry rate and the terrain slope in the chemical elements losses from the soil. This work aimed to quantify water and chemical element losses by surface runoff due to terrain slope and pig slurry rate (PS) in two soils with contrasting textures. Two trials were evaluated in 2018 and 2019 in Cambisol and Nitisol. Rates of 0, 22.5, 45, and 90 m 3 ha −1 yr −1 of PS were applied superficially in sites with slopes ranging from 10% to 35%. Perennial forage grass Tifton 85 (Cynodon dactylon) was grown as summer crop and ryegrass (Lolium multiflorum) was sown in the cold seasons in a field environment. Were determined the runoff, the volume of water, and chemical elements (Al, Ca, P, Mg, Cd, Cr, Cu, Mn, Fe, Pb, and Zn) lost by the surface runoff after natural rainfall. Increasing land slope elevated water losses substantially, on average 23.4 times in Cambisol and 10.8 times in Nitisol. This increase resulted in average increases of 27.6 and 12.4 times in the losses of the chemical elements analyzed for Cambisol and Nitisol, respectively. There was a reduction in water losses by surface runoff due to increased PS rates applied in both sites. The increased PS rate affected the losses of Cr and Cu in Cambisol and P, Mg, Cd, and Cu in Nitisol.The clayey soil potentiated the water and chemical elements losses by surface runoff in relation to the soil with lower clay content. Regardless of the soil, water and chemical element losses are maximized at higher slopes.

This study aims to evaluate the influence of the ground cover rate by crop residues and the rain time elapsed after the application of liquid swine slurry (LSS) under losses of water, sediments, and phosphorus (P). The study was carried out under a Humic Cambisols. Two areas were delimited: with and without the application of LSS. Each area was subdivided into four levels of crop residues: 5%, 35%, 65%, and 95%. Vegetable residues present in the area, from corn and black oat, were used. Three collecting gutters of 0.60 m² were installed in each subplot. Simulated rain was carried out on these, and the runoff volume collected for quantification and determination of losses. With LSS application, increase in the cover rate by crop residues reduces 0.3 mm h-1 the runoff volume and 1.67 mg m-2 reactive soluble P (H2O-P). The sediment losses in the first collection after the beginning of the rain were 23 times lower in the soil with 95% ground cover than in the soil with 5% ground cover. The loss of total P (total-P) decreases with the increase of the ground cover of the soil and increases in the same way with the increase of the time.