PREDICTING THE INCIDENCE OF IRON CHLOROSI S IN PEACH ORCHARDS CULTIVATED IN CALCAREOUS SOILS

Iron chlorosis is an economically important problem in peach (Prunus P ersica. (L.) Batsch) orchards cultivated in calcareous soils. To avoid erroneous decisions before planting peach it is highly recommended to know if a soil can induce Fe chlorosis. With this idea, soil samples and peach leaves were taken at 53 locations from 9 peach orchards in t he Lerida province and Andalusia (Guadalquivir River Valley). Soils we re sampled at depths of 25 and 50 cm. Total chlorophyll content (TCC) was measured in methanol extracts and estimated with the Minolta appar atus (SPAD units). TCC was well correlated with the SPAD units. Thus, SPAD readings can estimate the degree of Fe chlorosis in the field. Th e soil property best correlated with TCC was the Fe extractable with a mmonium oxalate at pH 3 (Fe-o) determined with a rapid extraction meth od. The Fe-o is mainly a measure of the poorly crystalline Fe hydr(oxi des). The F-o critical level for peach, which separates soils that ind uce Fe chlorosis from those that do not induce it, was approximately 1 g kg(-1) soil.