CORRECTING IRON DEFICIENCIES IN ANNUAL AND PERENNIAL PLANTS - PRESENT TECHNOLOGIES AND FUTURE-PROSPECTS

Correction of Fe chlorosis is done mainly by foliar sprays because soil applications generally are ineffective, especially for annual crops. Inorganic Fe sources applied to soils react rapidly to forms which are not as available to plants; ferrous Fe is oxidized to the ferric form in well-aerated soils, especially as soil pH increases. Several synthetic chelates and organic complexes have been used with varying success, depending upon Fe source and rate, application method, plant species, and weather and soil conditions. Use of Fe-efficient cultivars is one method of counteracting Fe deficiencies in some species. Future prospects for improving control of Fe chlorosis lie more with development of Fe-efficient cultivars of Fe-sensitive species than with development of improved Fe fertilizers and methods of application. The techniques of molecular biology should be applicable to help solve this important plant nutrition problem, but priority has not been given to conduct this research at this time.