Cm. Borkert et al., SOYBEAN RESPONSE TO FERTILIZATION AND POT ASSIUM AVAILABILITY IN LATOSSOLO ROXO-ALICO (OXISOL), Pesquisa agropecuaria brasileira, 32(11), 1997, pp. 1119-1129
Double-cropping soybean-wheat has been cultivated in the Latossolo Rox
o Blico (Haplorthox) soils of Parana State, Brazil, since the 70's. Du
e to credit restrictions to agriculture. since then most farmers have
not used fertilizers for soybean or applied less potassium than that r
emoved by the seeds. This system leads to low soil fertility and as a
consequence low yields. With the objective to study the best technolog
y for potassium fertilization and its residual effects on the soybean,
a long term experiment was run in a Latossolo Roxo alico soil, in Cam
po Mourao County. In the first five growing seasons, 1983/84 to 1987/8
8, it was applied, once a year, the doses of zero, 40, 80, 120, 160 an
d 200 kg of K2O/ha in the sowing row and broadcasted. In the next five
growing seasons, soybean was cultivated on the residual effect of the
potassium fertilization and also it was studied its effects on K-plan
t tissue and soybean yield. It was concluded that Latossolo Roxo Blico
can not be cultivated for more than one year with the double-cropping
soybean-wheat system without replace the K-removed by the seed.