Intervalos de corte e doses de potássio no rendimento e qualidade da forragem do capim-tanzânia

Abstract

The experiment was carried out in field previously cropped with Tanzânia grass in November of 1997, at the Animal Science Department área of the Federal University of Lavras, from August of 2001 to May of 2002, objecting to evaluate the influence of four cutting intervals (4, 6, 8 and 10 weeks) and three K20 doses (0, 100 and 200 kg/ha) on production and forage quality ofPanicum maximum Jacq. cv. Tanzânia 1. Initially, a soilanalysis ofexperimental áreawas made; later on, maintenance fertilization was realized, by applying 150kg/haof N, as ammonium sulfate, 60 kg/ha ofP205, as simple phosphate, and50 kg/haof K20, as potassium chloride. The treatments were combined in a factorial 4x3 design, in randomized blocks with four replications. Theexperimental potassium fertilization was realized in broadcast method between lines of Tanzânia grass, in two applications. Linear increments oftiller height and dry matter (DM) of Tanzânia grass were observed by increasing cutting intervals. The tiller density and the leaf/stem relationship were independent of the applied treatments. Leaf área index (LAI) increased linearly withthe increase of the doses of K20 and, in an exponential way, with the increase of cutting intervals. The crude protein (CP) contents reduced in an exponential way by increasing of cutting intervals. The neutra! detergent fiber (NDF) and acid detergent fiber (ADF) presented increase linear behaviour with the increase of cutting intervals. Linear decreasing of Ca and Mg contents were observed by increasing the potassium fertilizer doses. The increase of cutting intervals promoted linear decreasing of K, exponential of P andquadratic of CaandMgcontents. Efficiency ofK, N and P utilization was evaluated. The largest K efficiency of use was verified by application the médium dose of K20. When considering the maintenance fertilization, the smallest efficiencies are observed for K in the largest doses of K20 but presenting a better plant nutrient usage. N and P presented, respectively, a low and médiumefficiency of nutrientusage by plants.