Residual effects of potassium and magnesium on soybean yield and on disease incidence in a cerrado dark-red latosol
DOI:
https://doi.org/10.1590/S1678-3921.pab1987.v22.14881Keywords:
Glycine max, Phomopsis, Colletotrichum truncatum, critical foilar K, critical foliar Mg level, crop residueAbstract
Soybean cultivar Paraná was grown in 1981-81 at EMBRAPA/CPAC, at Planaltina, Brazil, to determine the residual effects of levels of K and Mg applied in 1975, upon the yield and seed quality and the severity of diseases caused by Phomopsis spp. and Colletotrichum truncatum on soybean stems. Decreasing yields and seed quality were associated with decreasing soil K and/or Mg levels. Foliar K levels were directly related to soil K levels while foliar Mg levels were inversely related to soil K. Foliar K content of 1.3% was sufficient for maximum seed production. Annual return of crop residue increased soil K and Mg, foliar K and Mg, and cation exchange capacity but not soil organic matter. There was no difference among K treatments in amount of fruiting structures of C. truncatum andPhomopsis spp. on soybean stems.
