Alterações nutricionais no capim-marandu adubado com doses de nitrogênio e enxofre

Abstract

Pasture fertilization is among the most important practices to determine the yield per area, and nitrogen (N) and sulfur (S) have great relevance for the growth and nutritional value of forage plants.The objective of this study was to evaluate the influence of the N and S combinations on the nutritional characteristics of Brachiaria brizantha cv. Marandu cultivated in pots. The experiment was carried out in the greenhouse from November 2017 to January 2018. A fractionated 52 factorial scheme was used, with 13 combinations defined for N and S: 0; 0, 20; 0.40; 100, 10; 100, 30; 200.0; 200, 20; 200, 40; 300, 10; 300, 30; 400.0; 400, 20 and 400, 40 mg dm-3 , which were distributed according to a randomized block design with four replicates. Two cuts were made in the plants, occasions when the shoots were separated in emergent leaves, newly expanded leaf blades, ripe leaf blades and stems plus sheaths and roots in the second cut. N and S concentrations were evaluated in plant parts and SPAD value in the diagnostic leaves. The data were analyzed by the F test adopting the level of 5% of significance. For the significant N x S interactions a polynomial regression study was carried out and for the effect of N and / or S doses alone a first and second degree regression study was performed. Marandu grass presented a positive correlation between SPAD values and nitrogen doses, indicating forage quality improvements due to the addition of N and influencing the photosynthetic capacity. The maximum concentration of nitrogen and sulfur occurs in mature leaves and roots, respectively, of Marandu grass. The concentrations of nitrogen and sulfur in the aerial part reach maximum values when higher doses are applied to the soil. The application mainly of nitrogen, but also of sulfur, influences the nutritional state of the marandu grass.