Frações de fósforo no solo após sucessivas aplicações de dejetos de suínos em plantio direto

Abstract

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.

Available content, surface runoff and leaching of phosphorus forms in a typic hapludalf treated with organic and mineral nutrient sources

“…and 3.0, 0.15 and 2.6 % of the total applied through NPK, respectively. These low values of P transferred via surface runoff in the different nutrient sources are similar to the results obtained by Bertol et al (2010), who observed P transfer via surface runoff of less than 15 % of the total applied and suggested that the P remains accumulated in the soil surface layer, as verified in the present study (Table 2) and in other studies (Adeli et al, 2008;Scherer et al, 2010;Ceretta et al, 2010a;Guardini et al, 2012a). Nevertheless, after successive manure applications, there is a tendency for saturation of adsorption sites of the reactive particles of the soil.…”

“…That is because P is predominantly found in inorganic form in the manure, readily available to plants. This may be seen in figure 1, where the greatest available P contents were observed in the first days of soil incubation, which indicates that a large part of the P present in the manure is found in the inorganic form, which is the predominant form of accumulation in soils treated with manure (Chardon et al, 2007;Gatiboni et al, 2008;Ceretta et al, 2010a;Guardini et al, 2012a;Lourenzi et al, 2013). Furthermore, the absence of tilling in the no-tillage system favors P accumulation in the soil surface layers because, in the soil, the P may be adsorbed to the surface of functional groups of reactive particles, normally forming inner sphere complexes (specific adsorption) (Barrow, 1999).…”

“…Furthermore, the addition of high P quantities to the soil, especially in areas treated with successive manure applications, may reduce the binding energy between the ion and the functional group involved, due to saturation of the adsorption sites. There is thus P accumulation in inorganic labile fractions, especially in the soil surface layers, but also in deeper layers (Gatiboni et al, 2008;Ceretta et al, 2010a;Guardini et al, 2012a;Lourenzi et al, 2013). Among the methods used for evaluating P availability in the soil is the anion exchange resin (AER) method (Bolland et al, 1996;Berwanger et al, 2008;Guardini et al, 2012b), used for determining P availability to plants (CQFS-RS/SC, 2004) and also as an indicator of the contamination potential in soils with sequential application of animal manure (Guardini et al, 2012b).…”

Effects of Pig Slurry Application and Crops on Phosphorus Content in Soil and the Chemical Species in Solution

“…The movement of P in the profile probably occurred in soluble form, in view of the high concentrations found in the soil solution (Figure 1), by the water flow through the profile. But, although to a lesser degree, the migration of P in particulate form and by bioturbation may also have occurred, which is the movement of particles in biopores (Ceretta et al, 2010a). The migration of P in the profile, especially in soils with sandy texture, as in the Typic Hapludalf of this study, the risk of subsurface water contamination is greater, especially in soils where the water table is shallower, making the water unfit for human consumption (Sorensen and Rubaek, 2012;Girotto et al, 2013;Lourenzi et al, 2014).…”

Effects of pig slurry application on soil physical and chemical properties and glyphosate mobility

“…When these sites are saturated, P can be leached by water, percolating through the soil profile. Losses of P by leaching or surface runoff, when attached to soil colloids, present a risk of degradation of groundwater and surface waters, respectively (Ceretta et al, 2010). Berwanger et al (2008) found that pig slurry application at the surface of an Ultisol soil resulted in nutrient loss by surface runoff, while Djodjic et al (2004) reported nutrient losses by leaching.…”