Yield and Leaf Mineral Compositions of Kiwifruit According to Different Fertilization Methods

Kiwifruit requires high quantity of nutrients, which must be supplied through fertilization to obtain optimum yield on sustainable basis. Therefore, this research was conducted with the objective of evaluating different fertilization methods -including broadcast application (as control), localized placement of fertilizer, and fertigation alone or in combination with foliar application- on leaf and fruit nutrient contents of kiwifruit. In addition, this experiment was conducted in order to determine relationships between the leaf and fruit mineral compositions with yield of kiwifruit vine in Iran Citrus Research Institute of Ramsar. Results showed that Fertilization methods had a significant effect on yield and fruit weight and the highest level was observed in the combination of fertigation with foliar application. In addition, results showed that fertilization methods had a significant effect on leaf and fruit nutrient (nitrogen (N), phosphorus (P), potassium (K) and calcium (Ca)) levels of kiwifruit. Furthermore, foliar application increased leaf and fruit nutrient (N, P, K, Ca) levels of kiwifruit at all treatments. The fruit/leaf ratios of P, K, and Ca were different in various fertilization methods. In addition, the mineral concentration in fruit decreased in the order of K> N> Ca> P, and in leaf decreased in the order of N> K> Ca> P, regardless of fertilization method. The correlation results showed that kiwifruit yield had significant correlation with N, K, and Ca levels in kiwifruit leaves. However, the yield was not significantly correlated with fruit nutrient levels. In addition, by applying a stepwise variable selection program, leaf K content was found to be the most important variable for yield prediction. Moreover, leaf K content in combination with leaf N and Ca contents could be used for yield prediction in the studied vine. Since all kiwifruit orchards in the North of Iran are equipped with micro-jet irrigation system and also significant increase of nutrient concentrations in leaves following foliar application, fertigation and foliar application not only can save time and money but can also cause an increase in nutrient concentration in leaves and improve fruit quality.