Interactive Effects of Nitrogen Form and Oxygen Concentration on Growth and Nutritional Status of Eggplant in Hydroponics

Abstract

A greenhouse study was carried out to determine the effect of nitrogen forms and different O 2 levels on growth and mineral nutrient concentratio ns of eggplant. The experimental design was a completely randomized fac torial experiment with two factors, namely: (i) Two nitrogen forms (Ca(NO 3 ) 2 and (NH 4 ) 2 SO 4 ) and (ii) Three O 2 levels of the nutrient solutions (1 ± ±± ± 0.3, 2 ± ±± ± 0.3, 3 ± ±± ± 0.3, and 4 ± ±± ± 0.3 mg L -1 O 2 ). The results showed that ammonium application reduced all measured parameter s of vegetative growth, whereas high oxygen levels increased the vegetative growth. Comparing with nitrate-N, ammonium application increased the concentrations o f NPK and Zn in leaves and Zn and Cu in roots, while it decreased the concentration o f Mg, Ca, Cu, Mn, and Na in leaves and Ca, Mg, Mn, and Na in roots. High levels of O 2 increased N, Mg, Ca, Cu, and Mn content of leaves, as well as Mn and Na content in roots, w hile it decreased the concentration of K in leaves and P and Zn in roots. According to the r esults, the increase in O 2 amount of the nutrient solutions partly alleviated ammonium toxic ity in eggplant. Therefore, in floating hydroponic cultures, O 2 level and its distribution should be controlled an d must not be lower than 4 mg L -1 . Keywords: Ammonium, Nitrate-N, Nutrient solution aeration, S oilless culture, Solanium melongena .