A NEW APPROACH TO FRONT CITRUS IRON CHLOROSIS: ORGANO-MINERAL FERTILIZERS FROM GLASS-MATRIX AND ORGANIC BIOMASSES

Abstract

The aim of the present paper was to investigate the agronomical responses of a fertilizer able to release nutrients on the basis of plant-demand, glass-matrix based fertilizer (GMF). Nutrient release was stimulated by mixing the glass-matrix with organic components such as digested vine vinasse (DVV) or meat-meal (MM), added with the aim to increase GMF biological affinity toward roots. Laboratory tests and short-term pots trials showed that the mixture GMF+DVV increased nutrient availability and plant growth. In the following stage these mixtures were tested for their ability to contrast in calcareous soils citrus iron chlorosis, one of major abiotic stresses affecting fruit tree crops in the Mediterranean area. Three year studies were conducted: i) in pots, on ‘Tarocco ScirA¨â€™ orange trees [Citrus sinensis (L.) Osbeck] grafted on Swingle citrumelo and ii) in field, on Tarocco grafted on sour orange rootstock [C. aurantium (L.) Osbeck], by comparing GMF and its mixtures with DVV and MM to a synthetic chelate application. The GMF+DVV mixture was able to supply adequately micronutrients, particularly iron, reducing the chlorosis symptoms, increasing the leaf SPAD index and concentration, and decreasing the Fe index.