Improvement of iron chlorosis and nutrient balance in peach and nectarine trees under the integrated fertilization management using DOP, DRIS, and CND methods

Knowledge of the nutritional status of orchards to increase the quantity and quality of the product is a necessary and unavoidable matter. Accordingly, this research was conducted to investigate the effect of fertilizing fruit trees with different integrated treatments of organic, chemical, and biological fertilizers on the correction of iron chlorosis in peach and nectarine trees and the balance of nutrients in the leaves and fruits of treated trees using three indices. Experimental treatments were applied in the form of deep-hole fertilization as follows: completely rotten manure (A), manure + urea + diammonium phosphate + Fe-EDDHA (B), manure + urea + diammonium phosphate + Fe-EDDHA + Bacillus (C), manure + urea + diammonium phosphate + Fe-EDDHA + Thiobacillus + powdered sulfur (D), and manure + urea + diammonium phosphate + Fe-EDDHA + Bacillus + Thiobacillus + powdered sulfur (E). The chlorophyll content in the leaves and N, P, K, Fe, Mn, Cu, and Zn contents in the leaves and fruits were measured during two consecutive years. The results reflected that the application of manure without using chemical and biological fertilizers in the treatment A led to a decrease in the leaf content of N, P, K, and Fe below the normal level. The use of mineral fertilizers along with organic fertilizer in the treatment B led to an increase in the levels of N, P, and Fe in the leaves. Although the addition of Bacillus solution to the treatment C increased the leaf content of these nutrients, they were still below the optimum level. Based on Cate-Nelson analysis of variance, the yields of 50.1 and 43.2 kg tree^-1 were obtained as critical limits to separate the high-yielding community (treatments D and E) from the low-yielding community (treatments A, B and C) in peach and nectarine trees, respectively. Nutrient balance indices (DOP, DRIS, and CND) showed that Fe and P were the most limiting nutrients in peach and nectarine leaves and fruits in the low-yielding community. According to the results, the integrated fertilization management in the treatment E had the greatest effect on improving iron chlorosis and showed a balanced and optimal nutritional instruction for peach and nectarine leaves and fruits in the calcareous soils. Reducing pH due to the use of sulfur and Thiobacillus was an effective strategy in increasing the availability of P and Fe in such soils along with the use of organic and mineral fertilizers.