Availability of some potassium sources by using sweet sorghum (Sorghum bicolor (L.) Moench)

Abstract

A field experiment was carried out, at Areão Experimental Farm of Escola Superior de Agricultura "Luiz de Queiroz", Piracicaba, São Paulo, Brazil, in a soil named "Terra Roxa Estruturada". The aim of this experiment was to study the effect of three potassic materials originated from Poços de Caldas, MG, Brazil, which were subject of hydrothermal treatment, on sweet or saccharine sorghum (Sorghum bicolor (L.) Moench) cv. "Start", in respect to the grains and stalks yields, the potassium contents of grains, stalks and leaves, the quantities of potassium extracted by grains and stalk and the ethanol. These potassic materials, including potassium cloride, were applied at two rates of K2O/ha (100 kg/ha K2O and 200 kg/ha K2O). According to the data, the following conclusion can be drawn: 1) One of these potassic materials showed the highest content of K2O soluble in 2% citric acid solution (26.02%) and gave the highest yield and the highest quantity of potassium extracted by the grain, when applied at the rate of 200 kg/ha K2O. 2) There was no difference between potassium sources and rates in respect to potassium content and quantity of this element extracted, in the stalk, but the potassium sources used in this experiment was superior to the control. 3) The potassium chloride when applied at the rate of 200 kg/ha K2O showed negative effect on grain yield, on concentration and quantity of potassium in the grain. 4) The potassium sources increased the quantity of total sugar and ethanol yield in respect to the control .