Soil pH and Extractable Elements under Blight-affected and Healthy Citrus Trees on Six Florida Soils

Abstract

Abstract Citrus trees affected with blight, a disease of unknown cause, were associated with soils having higher pH and Ca levels than soils under healthy trees. A detailed study of soil samples taken in 5-cm increments to a depth of 45 cm under healthy and blight-affected trees from five sites showed that pH, determined separately for each increment, showed significantly lower mean pH values under healthy trees. Double-acid (0.05 N HCI and 0.025 N H2SO4) extracts of soil under blighted trees contained more Ca at all five sites. Higher P and K were associated with blight in three of six and four of six comparisons, respectively. In one of five sites, Mn and Zn were higher and Fe lower under blighted trees. The soil under trees in very early stages of blight in the heavily affected part of a block compared with soil under trees in the healthy part of the block was higher in pH and Ca. Soil where lime was incorporated deeply by mixing or deposition of dredged calcareous subsoil on the surface was associated with the most severe incidence of blight.