Author
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Wutscher, Heinz |
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Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/25/1996 Publication Date: N/A Citation: N/A Interpretive Summary: The cause of citrus blight, one of the most serious citrus production problems, remains unknown and many different approaches are taken to solve the problem. The approach through plant nutrition is promising, because many effects of blight are on uptake and internal distribution of mineral elements. Soil acidity affects solubility of nutrient elements and thereby availability and uptake by plants. Earlier work has shown that citrus blight does not occur on highly acid or alkaline soil and that the pH under blighted trees is slightly higher than under healthy trees. Because pH is only a small part of the total capacity of a soil to supply acidity, the relationship between citrus blight and the extent of how much of total acidity is in active (pH) form was investigated. The data show that under healthy trees more of the total acidity is in active form, thereby making many nutrient elements more available. Technical Abstract: The pH and the reserve (exchangeable) acidity of 147 soil samples, taken at 0 - 30 cm depth at eight locations covering most of Florida's citrus growing area, was determined using 1:1 soil:water for pH and the triethanolamine method for reserve (exchangeable) acidity. The percentage of "active acidity" (pH) of reserve acidity was calculated by the formula: [(mmol H= of active acidity x 100) / (mmol H+ reserve acidity/kg soil)] x 1000. The samples were taken at the dripline of orange trees identified as "healthy" or "citrus blight affected" by standard diagnostic methods or in random patterns to get averages for whole areas. Soil pH was consistently about 1 pH unit higher under blight-affected trees and the percentage of active acidity of 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 blight-affected trees in two locations in distinct production areas. |
