Corn fertilization with ammonium sulfate in a Brasília Cerrado soil under Brachiaria decumbens pasture. / Fertilização com sulfato de amônio na cultura do milho em um solo de cerrado de Brasília sob pastagem de Brachiaria decumbens.
Antonio Xavier de Campos
DATA DE PUBLICAÇÃO
Crop/livestock integration systems have been adopted in the cerrados, since this is a technology for pasture recovery and renovation, used in association with annual crops, such as corn. In this system, the pasture is recovered and maintained productive by crop fertilization. Nitrogen is prominent among the nutrients applied in fertilizations; it undergoes several transformations in the soil, and its efficiency can be compromised by application seasons and rates in Brachiaria grass fertilized prior to sowing, and/or as sidedressing in corn. The objective of this work was to determine nitrogen rates in the form of ammonium sulfate and to establish application for this nutrient if prior to seeding and/or as sidedressing in corn, under a crop/livestock integration system. The experiment was developed at Universidade de Brasília-UnBs Farm, in a degraded Brachiaria decumbens pasture implemented on a typical Dystrophic RED-YELLOW LATOSOL. The soil was corrected with dolomitic lime (1.3 Mg ha-1) and received corrective fertilization with 80 kg ha-1 P2O5, 50 kg ha-1 K2O in the form of single superphosphate and potassium chloride, respectively. Nitrogen in the form of ammonium sulfate, at the rates of 60 and 120 kg ha-1, was applied manually prior to seeding (73 days before corn seeding), at the furrow positions where corn was to be sown. The Brachiaria grass was desiccated with the herbicide paraquat (2 L ha-1) in two applications. Single hybrid corn AG-450 was sown manually, in furrows spaced 0.80m apart, resulting in a population of 62,500 plants per hectare. Fertilization at corn seeding in all treatments consisted of 30 kg ha-1 N, 110 kg ha-1 P2O5, and 70 kg ha-1 K2O, applied in the form of ammonium sulfate, single superphosphate, and potassium chloride, respectively. Corn sidedressing was performed manually at the V4 developmental stage of corn at the rates of 30, 60, and 120 kg ha-1 N in the form of ammonium sulfate; the application also included 30 kg ha-1 zinc sulfate. A treatment without fertilizer (0 kg ha-1 N) was included both before seeding and as sidedressing, but receiving the rate of 30 kg ha-1 N at corn seeding as ammonium sulfate and 30 kg ha-1 zinc sulfate during the sidedressing application. The experimental design was randomized blocks in a split-plot scheme with 12 treatments and 4 replicates. The 12 treatments containing N rates corresponded to corn pre-sowing and sidedressing N rate combinations. Microplots were included in the plots of treatments 120-0 and 0-120, respectively, applied prior to sowing and as sidedressing, containing 15N-labeled ammonium sulfate rates (120 kg ha-1). Soil and plant tissue analyses were carried out, dry mass was quantified, and the % of nitrogen recovery from the 15N-labeled ammonium sulfate was determined. The mean dry mass values in the plant tissue and in corn grain showed yield increases when nitrogen was applied as sidedressing, but were not significant in the pre-seeding application. The best dry mass yield responses were obtained with N rates (kg ha-1) of: 120-70 and 60-85, applied before seeding and as sidedressing, respectively. The highest grain yields were verified at N rates of 60-60 and 0-96 kg ha-1 applied before seeding and as sidedressing in corn, respectively. N recovery from the ammonium sulfate was 79 and 40%, when applied as sidedressing and before seeding, respectively.
capim braquiária milho pastagem cerrado semeadura brachiaria grass nitrogen fertilizers cobertura do solo soil sidedressing fertilization fertilizantes nitrogenados cerrado pasture corn sowing fertilização
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