Potential phosphorus leaching from sandy topsoils with different fertilizer histories before and after application of pig slurry

This study investigated the effects of historical long-term and recent single applications of pig slurry on P leaching from intact columns of two sandy topsoils (Mellby and Böslid). The soils had similar physical properties, but different soil P status (ammonium lactate-extractable P; P-AL) and degree of P saturation (DPS-AL). Mellby had P-AL of 220-280 mg kg-1 and DPS-AL of 32-42%, which was higher than for Böslid (P-AL 140 mg kg-1 and DPS 21%). The study investigated the effects since 1983 of four treatments with different fertilizer histories, in summary high (HighSlurryMellby) and low (LowSlurryMellby) rates of pig slurry and mineral P (MinMellby) applications at Mellby and mineral P application at Böslid (MinBöslid). The columns were irrigated in the laboratory five times before and five times after a single application of pig slurry (22 kg P ha-1). Concentrations of dissolved reactive P (DRP), dissolved organic P and total-P (TP) in leachate and loads were significantly higher (p <0.005) from the treatments at Mellby than those at Böslid. TP concentrations followed the trend: HighSlurryMellby (0.57-0.59 mg L-1) > MinMellby (0.41-0.49 mg L-1) > LowSlurryMellby (0.31-0.36 mg L-1) > MinBöslid (0.14-0.15 mg L-1), both before and after the single slurry application. DRP concentrations in leachate were positively correlated with DPS-AL values in the topsoil (R2=0.95, p<0.0001), and increased with greater DPS-AL values after the single slurry application (R2=0.79, p<0.0001). Thus, DPS-AL can be an appropriate indicator of P leaching risk from sandy soils. Moreover, the build-up of soil P due to long-term repeated manure applications seems to be more important for potential P losses than a single manure application

Influence of soil phosphorus and manure on phosphorus leaching in Swedish topsoils

In Sweden, subsurface transport of phosphorus (P) from agricultural soils represents the primary pathway of concern for surface water quality. However, there are mixed findings linking P in leachate with soil P and limited understanding of the interactive effects of applied P sources and soil test P on P leaching potential. Identifying soils that are susceptible to P leaching when manure is applied is critical to management strategies that reduce P loadings to water bodies. Intact soil columns (20 cm deep) from five long-term fertilization trials across Sweden were used in leaching experiments with simulated rainfall to explore the interactive effects of dairy cow (Bos taurus L.) manure application, soil test P and cropping system. Strong relationships were observed between ammonium-lactate extractable P in soil and dissolved reactive P (DRP) concentrations in leachate, although regression slopes varied across soils. For three soils, application of manure (equal to 21-30 kg P ha-1) to the soil columns significantly increased DRP leaching losses. The increase in DRP concentration was correlated to soil test P, but with wide variations between the three soils. For two soils leachate P concentrations after manure addition were independent of soil P status. Despite variable trends in P leaching across the different soils, P concentrations in leachate were always moderate from soils at fertilization rates equivalent to P removal with harvest. Results clearly stress the importance of long-term P balance to limit P leaching losses from Swedish agricultural soils

Perdas de nutrientes via subsuperfície em colunas de solo sob fertilização mineral e orgânica Nutrient losses via leaching from soil columns submitted to mineral and organic fertilization

O uso de dejetos de animais na produção agrícola pode ocasionar a contaminação ou poluição das águas por nutrientes, principalmente com aplicações consecutivas na mesma área. Nesse sentido, o objetivo deste trabalho foi avaliar o efeito da aplicação de dejeto líquido de bovinos e fertilizantes minerais na lixiviação de NH4+, NO3-, P e K. Para essa avaliação, foram coletadas colunas indeformadas de solo, num experimento de campo que estava sendo conduzido por sete anos consecutivos e que continha 12 tratamentos, resultantes da combinação de quatro doses de dejeto líquido de bovinos com três doses de fertilizante mineral. O experimento de campo era conduzido num Latossolo Bruno distrófico em sistema de plantio direto com sorgo, milho, aveia-preta e azevém em rotação. Em laboratório, essas colunas, de acordo com os respectivos tratamentos de campo, foram submetidas à aplicação do dejeto líquido de bovinos (0, 30, 60 e 90 m³ ha-¹, aplicados em dose única) e dos fertilizantes minerais (0, 50 e 100 % da dose recomendada para o milho - 120, 60 e 60 kg ha-1 de N, P2O5 e K2O). Imediatamente após a aplicação de dejeto e fertilizante, a água percolada por coluna foi coletada e analisada em cinco turnos contínuos, totalizando 516 mm - aproximadamente três volumes de poros. Constatou-se aumento nas concentrações de N-NH4+, P e K com as doses de dejeto e aumento de N-NO3- e K com as doses de fertilizante mineral. No entanto, com exceção do N-NO3-, as concentrações de N-NH4+ e P estiveram abaixo do limite máximo permitido pela legislação brasileira, indicando a importância da infiltração de água no solo na redução do potencial poluidor dos dejetos.<br>The use of animal manure in agricultural systems can cause water contamination and/or pollution by nutrients, especially by consecutive applications to the same area. In view thereof, the purpose of this study was to evaluate the effect of manure and fertilizer application on NH4+, NO3-, P and K leaching. For this evaluation, undisturbed soil columns were collected from a seven-year field experiment that consisted of 12 treatments, resulting from the combinations of four doses of dairy slurry with three doses of mineral fertilizers. The study has been conducted on an Oxisol under no-till system with a crop rotation including sorghum, corn, oat and ryegrass. The leaching experiment was conducted in a laboratory with the undisturbed soil columns collected in the field experiment. In the laboratory, these soil columns, analogously to the respective field treatments, were treated with dairy slurry manure (0, 30, 60 and 90 m³ ha-¹ applied in a single dose) and mineral fertilizers (0, 50 and 100 % of the recommended dose for corn - 120 kg of N, 60 kg of P2O5 and 60 kg of K2O per ha) application. Immediately after manure and fertilizer application, the percolated water was sampled and analyzed in five continuous periods, totalling 516 mm, which corresponded to approximately three pore volumes. An increase of NH4-N, P, and K with increasing manure doses and an increment in NO3-N and K with the higher mineral fertilizer doses was observed. However, in general, except for NO3-N, the NH4-N and P concentrations were below the limit value determined by the Brazilian legislation, indicating the importance of soil-water infiltration to reduce the manure pollution potential