Irrigation depth and nitrogen doses on elephant-grass pastures during the rainy season in the north of Minas Gerais state

Abstract

It was evaluated during the rainy season in North of Minas Gerais the effect of four levels of nitrogen (100; 300; 500 and 700 kg/ha/year) and six water depths (0%; 20%; 40%; 80%, 100% and 120% of the reference evapotranspiration, or ETo) on the forage yield, tillers density, leaf/stem relationship, plants height and crude protein content and neutral detergent fiber of elephant grass (Pennisetum purpureum, Schum). The experimental design was in blocks at random with four replications. The water depths and doses of nitrogen increased lineally the dry matter production and the tillers density. The plants height presented a linear behavior proportionally to application of irrigation depths. The crude protein contents decreased linearly with the application of the irrigation depths and increased with the doses of nitrogen. Quadratic effect was provided by the irrigation to neutral detergent fiber content, with maximum percentage of 72,26%, when water depth of 96,25% of the ETo was applied. Nitrogen fertilization reduced the neutral detergent fiber content linearly. As much the application of the irrigation depths as the nitrogen fertilization one, acting separately or in interaction, did not affect the leaf/stem relation on the rainy season. The water depths associate to the doses of nitrogen raised the dry matter yield, thus evidencing the reduction of effect of production seasonality of the elephant grass “pioneiro” in the North of Minas Gerais.