Potássio no solo e na planta e produção de alfafa cultivada no sistema plantio direto sob doses de adubação potássica

Abstract

This trial aimed to evaluate the potassium fertilization effects (0, 50, 100, 200, 300, 400 and 500 kg K2O ha-1) over forage production and nutritive value of alfalfa in the Southwestern Paraná. The experiment was carried out from September 2010 to December 2011 in Pato Branco – PR. Completely randomized blocks experimental design with four replications and seven treatments (potassium – K - fertilization levels) were used. The total amount of K was splitted out on three applications on cover (summer, fall and spring). Potassium chlorate (KCl – 60%) was used. The evaluated variable were: total dry matter production (one year round), dry matter production per harvest, harvests frequencies, sward canopy high in the harvests events, aboveground K concentration, forage nutritive value (NDA, CP, TDN), K plant uptake, and K concentration at different soil depths. The data were analyzed by variance analysis (5% significance). Tukey test was used for qualitative variables and polynomial regression analysis for quantitative variables. None variable was affected by potassium fertilization levels, except K concentration in the soil, this one was also affected by date and depth sampling. Dry matter production, aboveground K concentration, crude protein content, and sward canopy height at the harvests, were only affected by date sampling.