Borkert CM, Sfredo GJ, Farias JRB, Castro C de, Spoladori CL, Tutida F. Residual effect of potassium fertilization applied to soybean in three different Oxisols. PAB. 1997;32(12):1227-1234. doi:10.1590/S1678-3921.pab1997.v32.4779