POTASSIUM IN THE EARLY DEVELOPMENT STAGE OF UNBURNED SUGARCANE RATOON

Abstract

In the mechanized harvesting without the use of fire, there is deposition of straw on the soil surface, which may be recycled and reduce the potassium fertilization for sugarcane, if compared to the burned sugarcane, what may reflect in a lower production cost. This study aimed to evaluate the potassium application effect in the early development of first cutting sugarcane ratoon (SP 89-1115), in an unburned harvesting system. The experiment was installed in a first sugarcane ratoon area, in a clay Oxisol. The treatments consisted of five K₂O doses (0 kg ha^-1, 32.5 kg ha^-1, 65.0 kg ha^-1, 130.0 kg ha^-1, and 195.0 kg ha^-1), as KCl, applied in 2009, in a randomized blocks design with five replications. The growth variables measured were number of tillers, plant height, and stem diameter, 120 days after budding. The potassium application provided a linear increase in the soil potassium content, at the 0-0.20 m and 0.20-0.40 m depth layers, reaching, respectively, 0.18 cmol_c dm^-3 and 0.12 cmol_c dm^-3, for the highest K dose. The K fertilization did not affect the number of tillers and stem diameter, but it affected plant height, which reached its highest value at 195.0 kg ha^-1 of K₂O.