Management of liquid swine manure: impact on mineral nitrogen dynamics and corn yield

ABSTRACT The agronomic efficiency of liquid swine manure (LSM) depends on the use of strategies to mitigate nitrogen (N) losses after its application to the soil, and thus preserve its fertilizing potential. In order to evaluate the injection of LSM into the soil and the addition of a nitrification inhibitor, as ways to increase its efficiency as a N source to the corn crop in the no-tillage system, an experiment was carried out under an Aluminofferic Red Latosol. The used treatments were: one control, surface application (total area) of LSM, injection of LSM in furrows, surface application (total area) of LSM + dicyandiamide (DCD), injection of LSM + DCD in furrows, and mineral fertilization. The mineral N in the soil and number of rows per ear, number of grains per row, 1,000-grain mass and grain yield for corn were evaluated. One day after the application of the treatments, the recovery of the mineral N in the soil with the injection of LSM exceeded by 10 kg ha-1 that observed with the superficial application. With DCD, the recovery of anionic forms (NO2- and NO3-) in the soil was lower in the first 20 days after the application, with the change in the N dynamics caused by DCD resulting in a higher content of mineral N at 30 days after sowing. The transformation rate for the anionic forms of mineral N in the soil is reduced with the addition of DCD. The injection of LSM with DCD does not differ from mineral fertilization, in terms of corn grain yield. RESUMO A eficiência agronômica do dejeto líquido de suínos (DLS) depende do emprego de estratégias para mitigar as perdas de nitrogênio (N) após sua aplicação no solo, e assim preservar seu potencial fertilizante. A fim de avaliar a injeção de DLS no solo e a adição de inibidor de nitrificação, como formas de aumentar sua eficiência como fonte de N à cultura do milho no sistema plantio direto, foi conduzido um experimento sob Latossolo Vermelho Aluminoférrico. Os tratamentos utilizados foram: uma testemunha, aplicação em superfície (área total) de DLS, injeção de DLS em sulcos, aplicação em superfície (área total) de DLS + dicianodiamida (DCD), injeção de DLS + DCD em sulcos e adubação mineral. Avaliaram-se o N mineral no solo e o número de fileiras por espiga, número de grãos por fileira, massa de mil grãos e a produtividade de milho. Um dia após a aplicação dos tratamentos, a recuperação de N mineral no solo com a injeção de DLS superou em 10 kg ha-1 o observado com a aplicação superficial. Com DCD, a re