In this paper we explore the accumulation of different phosphorus (P) fractions in soil submitted to successive applications of pig slurry (PS) and deep pig litter (DL). After 88 months of no-till crop cycles, soil samples were collected in the following treatments: control (C), PS applications equivalent to 90 and 180 kg N ha -1 (PS90 and PS180), and DL applications equivalent to 90 and 180 kg N ha -1 (DL90 and DL180). The cumulative application of P of the C, PS90, PS180, DL90 and DL180 treatment was 0, 303, 606, 825 and 1650 kg P ha -1 , respectively. The soil samples were then submitted to P chemical fractionation. Successive applications of 303 and 606 kg P ha -1 in PS form and 825 and 1.650 kg P ha -1 in DL form increased P levels down to 20 cm depth, especially in the labile inorganic fraction extracted by anion exchange resin and 0.5 M NaHCO 3 and to a lesser extent extracted by 0.1 M NaOH. Successive additions of PS180 and DL180 increased the levels of organic P extracted by 0.5 M NaHCO 3 , 0.1 M NaOH and 0.5 M NaOH, and successive applications of PS and DL caused P accumulation in the soil profile, especially in labile fractions. This increased the availability to plants, but also increases the potential for environmental contamination.

The State of Santa Catarina, Brazil, has agricultural and livestock activities, such as pig farming, that are responsible for adding large amounts of phosphorus (P) to soils. however, a method is required to evaluate the environmental risk of these high soil P levels. one possible method for evaluating the environmental risk of P fertilization, whether organic or mineral, is to establish threshold levels of soil available P, measured by mehlich-1 extractions, below which there is not a high risk of P transfer from the soil to surface waters. however, the mehlich-1 extractant is sensitive to soil clay content, and that factor should be considered when establishing such P-thresholds. The objective of this study was to determine P-thresholds using the mehlich-1 extractant for soils with different clay contents in the State of Santa Catarina, Brazil. Soil from the B-horizon of an oxisol with 800 g kg -1 clay was mixed with different amounts of sand to prepare artificial soils with 200, 400, 600, and 800 g kg -1 clay. The artificial soils were incubated for 30 days with moisture content at 80 % of field capacity to stabilize their physicochemical properties, followed by additional incubation for 30 days after liming to raise the ph(h 2 O) to 6.0. Soil P sorption curves were produced, and the maximum sorption (Pmax) was determined using the langmuir model for each soil texture evaluated. Based on the Pmax values, seven rates of P were added to four replicates of each soil, and incubated for 20 days more. following incubation, available P contents (P-mehlich-1) and P dissolved in the soil solution (P-water) were determined. a change-point value (the P-mehlich-1 value above which P-water starts increasing sharply) was calculated through the use of

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SUMMARYSuccessive applications of liquid swine waste to the soil can increase the contents of total organic carbon and nutrients and change acidity-related soil chemical properties. However, little information is available on the effects of swine waste application in solid form, as of swine deep-litter. The objective of this study was to evaluate alterations of organic carbon and acidity-related properties of a soil after eight years of pig slurry and deep-litter application. In the eighth year of a field experiment established in Braço do Norte, Santa Catarina (SC) on a sandy Typic Hapludalf samples were taken (layers 0-2.5; 2.5-5; 5-10; 10-15; 15-20 and 20-30 cm) from unfertilized plots and plots with pig slurry or deep-litter applications, providing the simple or double rate of N requirement of Zea mays and Avena strigosa in rotation. Soil total organic carbon, water pH, exchangeable Al, Ca and 0-2,5, 2,5-5, 5-10, 10-15, 15-20 e 20-30 cm, em

SUMMARYSuccessive applications of pig litter to the soil surface can increase the phosphorus (P) content and alter its adsorption, promoting P transfer to surface or subsurface waters. The purpose of this study was to evaluate P accumulation and the pollution potential of a soil after application of pig litter. In March 2010, eight years after the installation of an experiment in Braço do Norte, Santa Catarina, SC, Brazil, on a Typic Hapludult, soil was sampled (layers 0-2.5, 2.5-5, 5-10, 10-15, 15- 0-2,5; 2,5-5; 5-10; 10-15; 15-20; e 20-30 RESUMO: ACÚMULO E POTENCIAL CONTAMINANTE DO FÓSFORO EM UM ARGISSOLO COM APLICAÇÃO DE DEJETOS DE SUÍNOS As aplicações sucessivas de dejetos de suínos na superfície do solo podem aumentar o teor de fósforo (P) e alterar a sua adsorção, potencializando a transferência para as águas superficiais ou subsuperficiais. O presente trabalho objetivou avaliar o acúmulo e o potencial contaminante do P em um solo com aplicação de dejetos de suínos. Em março de 2010, após oito anos da instalação de um experimento localizado no município de Braço do Norte, Santa Catarina (SC), sobre um Argissolo Vermelho, foram coletadas amostras de solo nas camadas de