Effect of nitrogen and potassium fertilization on fruit yield and quality in kiwifruit

Abstract

ABSTRACT In this research, increasing doses of nitrogen (8-16-24-32 kg N da-1) and potassium (0-8-16-24-32-40 kg K2O da-1) fertilizers were applied to Hayward kiwifruit (Actinidia deliciosa) to determine their effects on the yield and some fruit quality characteristics. The research was started in a kiwi orchard established in 2004 in Ordu, in the vegetation period of 2015-2016, and was carried out in a randomized block design with 4 replications for two years. In general, the yield decreased with increasing N rates while it increased irregularly with the increasing K rates, and the highest yield was achieved by applying 24 kg of N and 40 kg of K2O per decare in both years. Nitrogen fertilization provided a somewhat increase in fruit weight in the first year and tended to decrease in the second year. Total antioxidant capacity generally showed a fluctuating trend in the first year and an increasing trend in the second year considering the nitrogen application. With increasing potassium applications, the total antioxidant activity and vitamin C content of fruits increased up to a certain level and then decreased. Total soluble solids content (SSC) and titratable acidity (TA) generally tended to decrease with potassium applications. Although fruit firmness generally varied considerably with nitrogen and potassium applications, higher fruit firmness was observed at higher doses. Nitrogen application generally increased the total phenolic content. When the yield, fruit weight and fruit quality were evaluated together, it was determined that 16 kg N and 32 kg K2O application per decare was more appropriate.