SOIL ACIDITY AND CITRUS BLIGHT

The pH and the reserve (exchangeable) acidity of 147 soil samples, tak en at 0-30 cm depth at eight locations covering most of Florida's citr us growing area, were determined using a 1:1 soil:water ratio for pH a nd the triethanolamine method for reserve (exchangeable) acidity. The percentage of ''active acidity'' (pH) of reserve acidity was calculate d by the formula: mmol H+ of active acidity x 100/mmol H+ reserve acid ity kg(-1) soil x 1000 The samples were taken at the dripline of orang e trees identified as ''healthy'' or ''citrus blight affected'' by sta ndard diagnostic methods or in random patterns to obtain averages for the whole area. Soil pH was consistently about 1 pH unit higher under blight-affected trees and the percentage of active acidity to reserve acidity was significantly lower at six of seven sites. This percentage was inversely correlated (r=-0.88 and -0.66) with the percentage of b light-affected trees in two locations in distinct production areas.