Crop Response to Soil Acidity Factors in Ultisols and Oxisols in Puerto Rico V. Sweet Potato

Abstract

The effect of various soil acidity factors on yield and foliar composition of sweet potato (Ipomoea batatas (L). Lam) were determined in three Ultisols and one Oxisol. Sweet potatoes responded moderately in yield to variations in soil acidity factors of three Ultisols, but did not on the Oxisol. On the Ultisols, soil acidity factors had very little effect on leaf composition. Yield increased with increasing soil pH, decreasing exchangeable Al content and decreasing exchangeable Al/base ratio. When all the soils, except Coto, were grouped together, the ratio of exchangeable Al to exchangeable bases explained 83% of the variation, the percent Al saturation 79%, and pH only 66%. Highest yields were obtained when pH was above 5, percent AI less than 20% and the Al exchangeable bases ratio less than .2. The lack of response in the Oxisol seems to be related to a reduced Al activity resulting from a high Mn concentration in the soil solution. Apparently sweet potato is very tolerant to high Mn concentrations in the soil solution.