ABSTRACT: The use of animal-origin residues as a nutrient source without prior and proper investigations on their positive and negative impacts can affect the quality of agricultural soils and the environment into which they are inserted. In this sense, the aim of this study was to assess the impact of swine wastewater and mineral fertilization application on soil, soybean crop, and leachate characteristics. The experiment was developed in drainage lysimeters under field conditions. The following doses of swine wastewater were applied: 0, 100, 200, and 300 m3 ha−1, both with and without mineral fertilization. Swine wastewater application contributed to increasing soil nutrients; however, a special attention should be paid to Cu+ and Zn+ accumulation, which may interfere with soil quality in the long-term. In addition, Na+, K+, and N can be leached into groundwater and cause impacts on water quality. Wastewater supplied soybean crop requirements with some nutrients such as K+ and Zn2+, without the need for an additional mineral supplementation. Thus, once the above conditions are monitored, swine wastewater can be applied to soil.

ABSTRACT: Soil application of swine wastewater for nutrient cycling may represent a correct destination of these residues and reduction in production costs. However, when applied to soil, such residue may cause environmental impacts. This study aimed to analyze the chemical characteristics of the soil, corn, and leachate after successive swine wastewater applications associated with mineral fertilization. The experiment was developed in drainage lysimeters under field conditions. Wastewater doses applied were 0, 100, 200, and 300 m3 ha−1 with and without mineral fertilization. The results were submitted to analysis of variance and Tukey's test. After nine years of application, a special attention should be taken regarding water quality from a dose of 200 m3 ha−1 since some elements may leach into the soil. In addition, a synchronism between residue application and crop requirements needs to be taken into account. Doses of 200 and 300 m3 ha−1 are considered as satisfactory to meet corn nutritional requirements. Moreover, an increase in fertility characteristics was observed, but a caution regarding Cu and Zn contents should be taken since these elements produce a cumulative effect in the soil.

RESUMO Em longo prazo a água residuária da suinocultura pode oferecer benefícios à relação solo-planta, quando planejado o uso e monitorados possíveis impactos ambientais. O objetivo do trabalho foi investigar os efeitos da aplicação continuada de água residuária de suinocultura associada com adubação mineral após seis anos de manejo em plantio direto e sucessão de culturas (14 ciclos de produção) acerca das condições químicas do solo e da cultura do milho. As doses de água residuária foram 0, 100, 200, 300 m3 ha-1 durante o ciclo. Simultaneamente foram avaliados os efeitos da associação de adubação mineral na semeadura com água residuária de suinocultura. A água residuária da suinocultura na dose de 100 m3 ha-1 proporcionou disponibilidade e absorção de P, K+, Mg2+ e Zn2+ sem causar toxicidade às plantas ou danos ao solo constituindo viabilidade de reúso de água e fertilização alternativa de baixo custo ao produtor. Os nutrientes N, P, K+ e B devem ser complementados com adubação mineral. Atenção especial deve ser direcionada ao acúmulo de Zn2+ no solo, ao longo do tempo de aplicação de água residuária da suinocultura.

ABSTRACT In the long run, swine wastewater can provide benefits to the soil-plant relationship, when its use is planned and the potential environmental impacts are monitored. The objective of this study was to investigate the effects of continuous application of swine wastewater, associated with mineral fertilization, after six years of management in no-tillage and crop rotation (14 production cycles), on the chemical conditions of the soil and the corn crop. The doses of wastewater were 0, 100, 200, 300 m3 ha-1 during the cycle. The effects of the association between mineral fertilization at sowing and swine wastewater were evaluated simultaneously. Swine wastewater at the dose of 100 m3 ha-1 promoted availability and absorption of P, K+, Mg2+ and Zn2+ without causing toxicity to plants or damage to the soil, constituting a viable, low-cost alternative of water reuse and fertilization for farmers. The nutrients N, P, K+ and B must be complemented with mineral fertilization. Special attention should be directed to the accumulation of Zn2+ in the soil along the time of swine wastewater application.