TRUNK INJECTION OF IRON COMPOUNDS AS A TREATMENT FOR OVERCOMING IRON CHLOROSIS IN APPLE-TREES

Severely chlorotic ''Red Delicious'' apple trees growing on a calcareous soil were treated for iron (Fe) chlorosis with pressure injections of 1.0% (w:w) solutions of ferrous sulfate, ferric citrate or Fe-Sequestrene 330 (Fe-330). Injections were made in Sept. of 1981 and in April, June and July of 1983. All treatments increased chlorophyll concentrations compared to controls, and treatments made in Sept. of 1981 and in April and June of 1983 increased shoot growth during the 1983 growing season compared to controls. Although the treatments did result in a temporary increase in foliar Fe content, there was not a strong correlation between foliar Fe and chlorophyll concentration. Ferrous sulfate and Fe-330 were more effective than ferric citrate in alleviating chlorosis. Injections made in April and June of 1983 greatly increased bloom in May of 1984, compared to trees injected in July of 1983 and the untreated controls. Hence, injections should be made early in the season (before July) in order to promote bloom the following growing season.