Crop Response to Soil Acidity Factors in Ultisols and Oxisols in Puerto Rico. X. Pigeon Peas

Abstract

The effect of various soil acidity factors on yield and leaf composition of pigeon peas [Cajanus cajan (L.) Huth] was determined in two Ultisols and one Oxisol. Pigeon peas barely responded in yield to soil acidity levels in the Oxisol, but responded strongly to variations in soil acidity in the two Ultisols. Yields increased from almost zero at the highest level of acidity (about pH 4 and 80% Al saturation) to more than 8 t/ha at about pH 6.0 with no exchangeable Al present. Yields increased with increasing soil pH, decreasing exchangeable Al content, and increasing exchangeable Al:Ca ratio. Yields were highest when pH was about 6.0, exchangeable Al was less than 20%, and exchangeable Al:Ca was less than 1.0. Soil acidity did not affect leaf composition, except that Ca content decreased with increasing acidity and correlated well with yields, ranging from about 0.5% with lowest yields to more than 1% with the highest yields. Number of nodules per plant was not affected by acidity factors, except at the highest level of acidity, at which no nodules were found.