Milho cultivado sob diferentes lâminas de irrigação e adubação nitrogenada

Abstract

Nitrogen fertilization and irrigation are fundamental to increase yield of maize crop, mainly in the State of Alagoas, where it is cultivated in technological deficiency. The objective of this work was to evaluate the growth, development and productivity of maize (Zea mays L.) under irrigation levels and nitrogen rates in the region of Tabuleiros Costeiros of Alagoas. The experiment was conducted in the experimental area of the Agrarian Sciences Center (CECA) of the Federal University of Alagoas (UFAL) in a randomized block design, in subdivided plots. The maize genotype used was AG 7088 VT PRO3, submitted to irrigation levels (40%, 80%, 120%, 160% e 200% da ETc) and nitrogen fertilization (N): (0, 75, 150 and 225 ha-1) doses. During the crop cycle, phenology was evaluated as a function of the thermal availability, growth as a function of irrigation and nitrogen adjusted to three growth models: logistic, Boltzmann sigmoidal and normal log peak, production function for AG7088 maize under irrigation and Nitrogen rates, water use efficiency for the cultivar studied. The results obtained in the treatments were submitted to analysis of variance by the F test (p ≤0.05) and, when there was a significant effect, regression curves at t (p ≤0.05) were performed. The vegetative development took approximately 107 DAS, accumulating 1,691.4 Degrees day (GD). The growth models showed a significant adjustment for the analyzed variables. It was observed that the ear insertion height of 1.37 (m) with the application of the irrigation blade 120 mm, and 1.34 m applying the dose of 174.5 kg of N ha-1. Green biomass for silage (VHL) was estimated with 174.23 kg of N ha-1, generating a production of 52,249 kg ha-1. The dose for (BVF) was 189 kg of N ha-1, promoting 54,080 kg of BVF ha-1. The final dry biomass (BSF) was reached with the dose of 159.58 kg of N ha-1, generating 15,424 kg of BSF ha-1. For the production components, there was influence of nitrogen fertilization at F (p ≤0.01), except for ear diameter (DE) and number of grain lines per spike (NLGE) F (p ≤0.05). The maximum agricultural yield (t ha-1) estimated was 7.97 t ha-1, obtained with the dose of 171.82 kg of N ha-1. The maximum dose of 184.75 kg ha-1, promoted the highest weight of a thousand grains (PMG), with a value of 254.21 (g). The maximum ear length (EC), 15.89 cm, was estimated with 187.26 kg of N ha-1. The maximum efficient dose for the number of grains per line (NGL) was 192.14 kg of N ha-1, equivalent to NGL of 33.84. The number of grains per spike (NGE) maximum, 615, 51, was estimated at the dose of 173, 22 kg of N ha-1. Nitrogen has an effect on the variables studied, up to a maximum point, with a tendency to decrease after reaching it. The agronomic efficiency decreases when increasing the doses of N in coverage.