Nitrogen uptake and macronutrients distribution in mango trees (cv. Keitt) under three N fertigation treatments

We assessed the effects of N concentration in the irrigation water on nutrient uptake and distribution in leaves and fruit of mango cv. Keitt grown in a lysimeter for four years. We applied three treatments: N1 - no N fertilization (less than 2 mg/L in the tap water); N2 - 10 mg/L N; N3 - 20 mg/L N. Deficient N conditions (N1) generated low vegetative yield, high fruit:leaf ratio, high photosynthetic activity, high leaf P and K concentrations, and high sugar content along with low acidity in the fruit. Excess N concentration (N3) induced vegetative growth, and reduced fruit yield and gas-exchange characteristics. The calculated annual nitrogen uptake heavily depended on the nitrogen supply (N1-26 g/tree; N2-196 g/tree; N3- 185 g/tree). Fruits were the major N sink being 0.82, 0.26 and 0.05 from the total annual N supplied. The N quantities accumulated in N1 fruits during the reproductive season (May-August), were above the N quantities supplied via fertigation, suggesting that N reserve in the vegetative tissues supplied the fruits high N demand. The finding shows the importance of adequate nitrogen supply to mango trees and the dangers of excessive fertilization.