The effect of pre-harvest treatment of calcium nitrate and iron chelate on post-harvest quality of apple (Malus domestica Borkh cv. Red Delicious)

Abstract

Enhancing the nutrition of fruit trees and crops with chemical fertilizers is one of the most important tools to increase production and improve crop quality during the harvest stage. In East Azerbaijan, apples are grown on calcareous soils, and managing tree nutrition is a precursor to increasing fruit yield and post-harvest fruit quality. A factorial experiment was conducted in a completely randomized block design in a Red Delicious apple orchard to investigate whether the application of calcium nitrate (Ca(NO3)2) at 50, 100, and 150 g tree−1 and iron (Fe) chelate (6% Fe) at (10, 20, and 30 mL tree-1) to the soil are beneficial. The fertilizers were applied at three times during fruit development: stage of cell division in young fruit, stage of peak rate of cell expansion and starch accumulation, and stage of cell expansion and the beginning of starch decline. The addition of Ca(NO3)2 and Fe-chelate affected fruit yield and fruit traits in storage, including total carbohydrate, pH, phenol, ripening index (TSS/TA), TSS, TA, fruit firmness, and weight loss. Fertilizer application also altered the concentration of some mineral nutrients in leaves and fruits. There was an interaction between storage time × Ca× Fe on fruit firmness, total carbohydrate, TSS, pH, and TA fruit. Fertilization with Fe-chelate increased fruit Ca and leaf Fe. Overall, the combination of 50 g Ca(NO3)2 and 30 mL Fe-chelate is recommended for apple orchardists in this part of Iran.