SOYBEAN RESPONSE TO POTASSIUM AND PHOSPHO RUS IN A PALEUDULT SOIL AT BALSAS, MA

With the expansion of soybeans to the low latitude region of Brazil, s tudies to establish new technologies for the crop are necessary since very little research has been done in that area. Usually recommendatio n for soil fertilization and liming are based on information adapted f rom other regions. With the objective of evaluate P and K fertilizatio n, a field experiment was conducted during the 1984/85 and 1985/86 sea sons, in the county of Balsas, MA, Brazil. The dosages of K were: 0, 4 0, 80 and 120 of K2O/ha(-1), in the first year, and 0, 50, 100 and 150 kg K2O/ha(-1) in the second year. P was applied at 0, 80, 160, 240 P2 O5/ha(-1) in the first year and 0, 100, 200 and 300 kg of P2O5/ha(-1) in the second year, applied to the planting rows. The research was con ducted in a Paleudult soil that had been cultivated with high land ric e for two previously years, without fertilization or liming. Three ton s/ha(-1) of lime and 10 kg of Zn/ha(-1) in addition to the inoculant a pplied to the seed (200 g/50 kg) were used. The results showed great r esponse to P with maximum yield at dosages close to 200 kg of P2O5/ha( -1) and the economical dose of 150 kg/ha(-1) during the two years of s tudy. For potassium, maximum yield was obtained with 50 kg of K2O/ha(- 1), and the economic dose bellow zero.