Cultivo do milho sob diferentes lâminas de irrigação e doses de nitrogênio, na região de Rio Largo, Alagoas.

Abstract

The availability of water in the soil is the most important factor for the growth and development of maize. The objective of this work was to evaluate the growth, development and agricultural yield of maize (Zea mays L.) under irrigation levels, in the region of Rio Lago, Alagoas. The experiment was done at the Agricultural Sciences Center of the Federal University of Alagoas, from 11/2017 to 03/2018. The statistical design was randomized blocks in the scheme of subdivide plots, with 20 treatments and four replications. The crop was irrigated by drip irrigation system, submitted to five irrigation levels (40, 80, 120, 160 and 200% of crop evapotranspiration - ETc) and four nitrogen fertilization rates (0, 75, 150 and 225 kilograms of nitrogen per hectare). The total values of rainfall, ETo and ETc during the growing cycle were 367, 536 and 460 mm, respectively. The interaction between the irrigation levels and the nitrogen fertilizer was not significant. So the effects of the treatments were analyzed independently, without unfolding. The number and mass of grains per ear and agricultural productivity were influenced by the irrigation levels applied, at 5% of probability, by the F test. The highest values of canopy height (247,2 cm), leaf area index (4,4), number of grains per ear (635,0 grains), grain mass per ear (195,0 g) 8,4 t ha-1) are produced with irrigation levels equivalent to 160% of crop evapotranspiration.The variables index of leaf area, number of grains per ear, grain mass per ear and agricultural productivity were adjusted to the quadratic polynomial model. While, the canopy height was better adjusted by the first order exponential model. The greatest efficiency in water use was 3.85 kg of cubic meter of water, with a 172.4 mm irrigation depth (40% of ETc), but this provided stresses to plants that imply lower growth and productivity.