RESUMO A compreensão dos fenômenos básicos da dinâmica do fósforo no solo é importante para a tomada de decisão sobre a necessidade de adição e para a definição das doses e dos modos de aplicação de fertilizantes fosfatados. As formas e o grau de labilidade do fósforo variam com as

RESUMOVolatilização de NH 3 é a principal reação que diminui a eficiência de utilização pelas plantas do N proveniente da ureia, quando ela é aplicada sobre a superfície do solo. A fim de minimizar essa perda, produtos têm sido misturados à ureia para inibir temporariamente a ação da urease. Este trabalho objetivou avaliar alternativas de aplicação de um fertilizante com inibidor de urease, visando a diminuir a volatilização de NH 3 relativamente à ureia convencional, em algumas condições ambientais e de solo. Foram desenvolvidos quatro experimentos, todos em condições de laboratório, em 2007 e 2008, em Cambissolo Húmico. Os tratamentos variaram em cada estudo e incluíram combinações de níveis de pH do solo (natural; 5,5; 6,3; e 6,8), umidade do solo (5, 10 ou 20 % de água) e temperaturas ambientais (18 e 35 ºC), além de estados físicos (sólido ou líquido) e de métodos de aplicação dos fertilizantes (na superfície ou incorporado ao solo). As unidades experimentais foram constituídas por bandejas plásticas (23 x 51 x 17 cm) com 12 kg de solo, numa espessura de 15 cm, sobre as quais foram instaladas câmaras coletoras de NH 3 . A amônia volatilizada foi determinada em várias épocas, nos primeiros 28 dias após a aplicação dos fertilizantes. O pico de volatilização diária de NH 3 ocorreu sempre na primeira semana depois da adição dos fertilizantes ao solo, e aconteceu dois a três dias mais tarde para a ureia com inibidor de urease, em relação à ureia convencional. A volatilização de NH 3 nem sempre foi maior para a ureia convencional em comparação ao fertilizante contendo inibidor de urease, tampouco para o estado líquido em relação ao granulado. A volatilização de NH 3 aumentou com a elevação do pH, da temperatura e da dose aplicada de N e foi menor nos extremos de umidade (solo com 5 % ou com 20 % de água). Para os fertilizantes aplicados sobre a superfície do solo, a taxa máxima de perda diária foi(1) Parte da Dissertação de Mestrado do primeiro autor apresentada à Universidade do Estado de Santa Catarina (UDESC).Recebido para publicação em fevereiro de 2010 e aprovado em dezembro de 2010.

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.

Resumo -O objetivo deste trabalho foi quantificar as frações de acumulação de fósforo em solo submetido a sucessivas aplicações de dejetos líquidos de suínos (DLS) em sistema de plantio direto. Em Santa Maria, RS, doses de 0, 20, 40 e 80 m 3 ha -1 de DLS foram distribuídas a lanço por sete anos agrícolas, antes do plantio de cada cultivo de inverno ou verão, em Argissolo Vermelho arenoso, totalizando 0, 584, 1.168 e 2.336 kg ha -1 de P aplicado via dejetos. O solo foi coletado nas camadas 0-2, 4-6, 8-10, 14-16 e 20-25 cm, e submetido ao fracionamento químico de P. A adição do DLS ao solo durante sete anos aumentou o teor de P até 25 cm de profundidade, principalmente nas frações inorgânicas extraídas por resina trocadora de ânions, NaHCO 3 0,5 mol L -1 e NaOH 0,1 mol L -1. As aplicações não aumentaram os teores de P orgânico extraído por NaHCO 3 0,5 mol L -1 , mas sim as frações orgânicas extraídas por NaOH 0,5 e 0,1 mol L -1 . O DLS adicionado ao solo por longo período pouco afeta a partição de P em frações inorgânicas e orgânicas. As sucessivas aplicações de DLS aumentam o acúmulo de P em frações predominantemente lábeis no solo, o que representa um risco potencial para contaminação de águas superficiais e subsuperficiais.Termos para indexação: esterco de suínos, fracionamento de fósforo, fósforo lábil, fósforo orgânico, risco de eutrofização, sistema de cultivo. Phosphorus fractions in soil after sucessive pig slurry applications in no-tillage systemAbstract -The objective of this work was to quantify the accumulation of phosphorus fractions in the soil subjected to successive pig slurry applications in a no-tillage system. At Santa Maria, Rio Grande do Sul state, Brazil, 0, 20, 40 and 80 m 3 ha -1 doses of pig slurry were broadcasted for seven years on Argissolo Vermelho arenoso (Arenic Hapludult) before sowing each winter or summer crop, totalizing 0, 584, 1,168 and 2,336 kg ha -1 of P from pig slurry. Soil samples were collected in 0-2, 4-6, 8-10, 14-16 and 20-25 cm layers and submitted to P fractionation. Applications of pig slurry during seven years increased P contents to a depth of 25 cm, especially in the inorganic fractions extractable by anion exchange resin, NaHCO 3 0.5 mol L -1 and NaOH 0.1 mol L -1 . Pig slurry doses did not increase P content in organic fractions extracted by NaHCO 3 0.5 mol L -1 , but increased the content of organic fractions extracted by NaOH 0.5 e 0.1 mol L -1. Pig slurry applied to soil for large period has little effect on the P partition in inorganic and organic fractions. Successive pig slurry applications increase P contents in the soil predominantly in labile fractions, which can represent a potential risk for waterbeds 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

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

ABSTRACT:Cover crops contribute to nutrient cycling and may improve soil chemical properties and, consequently, increase crop yield. The aim of this study was to evaluate cover crop residue decomposition and nutrient release, and the effects of these plants on soil chemical properties and on onion (Allium cepa L.) yield in a no-tillage system. The experiment was carried out in an Inceptisol in southern Brazil, where cover crops were sown in April 2012 and 2013. In July 2013, shoots of weeds (WD), black oats (BO), rye (RY), oilseed radish (RD), oilseed radish + black oats (RD + BO), and oilseed radish + rye (RD + RY) were cut at ground level and part of these material from each treatment was placed in litter bags. The litter bags were distributed on the soil surface and were collected at 0, 30, 45, 60, 75, and 90 days after distribution (DAD). The residues in the litter bags were dried, weighed, and ground, and then analyzed to quantify lignin, cellulose, non-structural biomass, total organic carbon (TOC), N, P, K, Ca, and Mg. In November 2012 and 2013, onion crops were harvested to quantify yield, and bulbs were classified according to diameter, and the number of rotted and flowering bulbs was determined. Soil in the 0.00-0.10 m layer was collected for chemical analysis before transplanting and after harvesting onion in December 2012 and 2013. The rye plant residues presented the highest half-life and they released less nutrients until 90 DAD. The great permanence of rye residue was considered a protection to soil surface, the opposite was observed with spontaneous vegetation. The cultivation and addition of dry residue of cover crops increased the onion yield at 2.5 Mg ha -1 .

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