Response of Soybeans to Liming as Related to Soil Acidity, Al and Mn Toxicities, and P in Some Oxisols of Brazil

The response of soybeans ( Glycine max (L.) Merrill) to the direct and residual effect of liming in relation to soil acidity, Al and Mn toxicities and P availability was studied in five Oxisols of Southern Brazil under successive wheat ( Triticum aestivum L.)‐soybean cropping. Yield responses to liming were highly significant due to the high exchangeable Al and extractable Mn, the low pH, exchangeable Ca + Mg, and available P found in these soils. Optimum yields were obtained when liming adjusted Al from 0.1 to 0.5 meq/100g (1.5% Al saturation), soil pH from 5.2 to 5.7 and Ca + Mg from 5.7 to 8.5 meq/100g. Liming also increased root nodulation and reduced P fixation and Mn levels in the soil.