Efeito de fontes nitrogenadas na produção do capim-marandu

Abstract

Nitrogen (N) is an essential nutrient and the macronutrient most required by plants, positively influencing the performance of forage grasses. The objective of this study was to quantify the dry matter mass (DM) of Brachiaria brizantha cv. Marandu after the application of nitrogen sources. The experiment was conducted in the experimental area of the Federal University of Mato Grosso, located in the municipality of Barra do Garças-MT. The experimental design was randomized blocks with eight treatments (1-Urea (46N); 2- Ammonium nitrate (34N); 3-Ammonium nitrate (34N) and potassium sulfate as sulfur source (18S); 4-Ammonium nitrate (34N) and calcium chloride as calcium source (24Ca); 5- Ammonium nitrate with calcium and sulfur (27N; 5Ca; 3.7S); 6- Ammonium nitrate with calcium and magnesium (27N; 4Ca; 2Mg); 7-Urea NBPT (32N); 8- Control) and four replications, in plots of 30 m². Before the application of the treatments, the aerial part of the Marandu grass was cut to level the height to 20 cm from the ground. The dose of N applied for the treatments was 120 kg ha-1 of N (divided into two applications). Five cuts were made of the aerial part of the Marandu grass. The growth of the Marandu grass was monitored daily with the aid of a ruler, and when the average height for all treatments was 35 cm, the cut was made 20 cm from the soil in a useful area of 0.5 m² per plot. The forage harvested was weighed to obtain the fresh matter mass. Subsequently, a sample of 500 g was removed and separated into the following parts: EF (expanding leaves), LR (blades of newly expanded leaves), LM (blades of mature leaves) and C+B (stem plus sheath). Then placed in a forced air circulation oven, with a temperature of 65°C for 72 hours, and weighed to obtain the dry matter mass of each component of the shoot. The data were analyzed by the F test and when significant the Skott knot mean test was performed at 5% probability. Increases of 46%, 298%, 93%, 58% and 539% of total DM of Marandu grass were observed between the control treatment and the most productive ones, respectively, N.A. + Ca + Mg, N.A. + Ca, N.A. + S, N.A + S+ Ca and Ammonium nitrate, respectively, for the first, second, third, fourth and fifth cuts. The nitrogen sources increased the productivity of Marandu grass when compared to the control.