Effects of organo-mineral glass-matrix based fertilizers on citrus Fe chlorosis

Abstract

Several citrus orchards develop symptoms of Fe deficiency when cultivated in calcareous and alkaline soils. In a field trial a new type of fertilizer, the glass-matrix based fertilizer (GMF, a by-product from ceramic industries) was applied. GMF is able to release nutrients, particularly Fe, on the basis of plant-demand, being nutrients not soluble in water, but only in acidic or metal complexing solutions. In our experiment, the effectiveness of GMF was tested on “Tarocco” orange trees of twenty years, severely suffering from Fe chlorosis, also by mixing GMF with meat meal (MM) or digested vine vinasse (DVV), thus comparing these treatments to the conventional Fe-chelate fertilization and the Fe-unfertilized control.The GMF+DVV mixture showed to be able to supply adequately micronutrients (particularly Fe) on long term, reducing the chlorosis symptoms, increasing the leaf SPAD index, Fe concentration and decreasing Fe index. No significant effect on yield and fruit quality was noticed. Our results indicated that these innovative formulates, and in particular glass-matrix based fertilizer mixed with digested vine vinasse, could be used as an “environmental friendly” fertilizer, allowing not only to reduce the use of chemicals (such as Fe-chelate), but also to re-use industrial wastes and organic residues which gave an “adding value” to these novel organo-mineral formulates.