Effect of organic calcium uptake and biostimulants during integrated nutrient management (INM) cultivation of kiwifruit cv. 'Hayward'

Foliar application with calcium (Ca) fertilizers improves quality and flesh firmness of kiwifruit and affects the mineral composition of leaves and fruits. The impact of preharvest foliar sprays, using a commercial fertilizer with organic Ca content in combination with an integrated nutrient management (INM) fertilizers and biostimulants was assessed for the quality properties and nutritional status of the kiwi cv. 'Hayward' over a 2-year period. Fruit flesh firmness increased under all organic Ca applications. In addition, all treatments resulted in elevated dry mass content, which is a common quality index. In leaves, the concentrations of N, P, K and B were higher compared to control. In fruits, the concentrations of N, B, K and Ca increased, in contrast to Mg, which was reduced. The content of Mn, Zn, Fe and Cu was not affected either in leaves or fruits. Application of organic Ca-fertilizers led to increased flesh firmness, total soluble solids, total acidity, and dry mass percentage. Foliar application with the addition of the biostimulant THEOFAST resulted in the elongation of stigmas area in kiwi cv. 'Hayward' fruits.