Crop Response to Soil Acidity Factors in Ultisols and Oxisols in Puerto Rico. VIII. Yams

Abstract

The effect of various soil acidity factors on yield and foliar composition of yams (Dioscorea alata L) were determined in two Ultisols and an Oxisol. The yam cultivar Smooth Statia responded strongly to variations in soil acidity in the two Ultisols. Yields decreased sharply as % Al saturation of the effective cation exchange capacity of the soil increased. Relative yields dropped to about 60% of maximum when Al saturation was only about 10%, and to 20% of maximum when Al saturation was 50%, a level common among Ultisols of Puerto Rico. The high sensitivity of this crop to soil acidity is shown by the fact that yields were sharply reduced when pH dropped from 5.6 to 5.1, a level at which most crops show little or no response to liming. Foliar composition was not affected by soil acidity, except that Ca content decreased with decreasing soil pH and increasing Al saturation. Yields of cultivar of the same species as Smooth Statia and known locally as Name de Palo were not affected by soil acidity levels in an Oxisol.