Optimizing Nitrogen Application for Growth and Productivity of Pomegranates

• Main Authors: Silit Lazare, Yang Lyu, Uri Yermiyahu, Yehuda Heler, Alon Ben-Gal, Doron Holland, Arnon Dag
• Format: Article
• Language: English
• Published: MDPI AG 2020-03-01
• Series: Agronomy
• Subjects: fertigation; nue; uptake; yield; vegetative indices; reproductive indices
• Online Access: https://www.mdpi.com/2073-4395/10/3/366

Quantification of actual plant consumption of nitrogen (N) is necessary to optimize fertilization efficiency and minimize contamination of earth resources. We examined the performance of fruit-bearing pomegranate trees grown in soilless media and exposed to eight N-fertigation treatments, from 5 to 200 mg N L^−1. Reproductive and vegetative indices were found to be optimal when 20 to 70 mg N L^−1 was supplied. Nitrogen application levels over 70 mg L^−1 reduced pomegranate development and reproduction. N uptake in low-level treatments was almost 100% and decreased gradually, down to 13% in 200 mg N L^−1 treatment. N usage efficiency was maximized under 20 mg N L^−1, in which case 80% to 90% of added N was taken up by the trees. At high N application, its efficiency was reduced with less than 50% utilized by the trees. Leaf N increased to a plateau as a function of increasing irrigation solution N, maximizing at ~15 to 20 mg N g^−1. Therefore, analysis of diagnostic leaves is not a valid method to identify excessive detrimental N. The results should be valuable in the development of efficient, sustainable, environmentally responsible protocols for N fertilization in commercial pomegranate orchards, following adaptation and validation to real soil field conditions.