Appropriate Ammonium-Nitrate Ratio Improves Vegetative Growth and Yield of Eggplant under Water Stress Conditions

Abstract

Water deficit in arid and semiarid regions limits eggplant (Solanum melongena L.) productivity and growth indicators. In this work, an experiment was conducted during two studied seasons of 2020 and 2021 on the farm belonging to the Central Laboratory for Agricultural Climate, Dokki, Giza governorate, Egypt. This work aimed to study the effect of different irrigation levels and nitrogen forms on the growth and yield of eggplant (Solanum melongena L., c.v. classic). Three irrigation levels, i.e., 50, 75, and 100% of irrigation requirements (IR), and three nitrogen forms, i.e., ammonium sulfate (NH 4 ) 2 SO 4 , calcium nitrate Ca(NO 3 ) 2 and ammonium nitrate NH 4 NO 3 were applied in a split-plot design with three replicates. Potential evapotranspiration (ET o ) was calculated using the Penman Monteith equation and then irrigation requirements for different irrigation rates were estimated. The obtained results showed that the highest vegetative growth, i.e., number of leaves, plant height, and total fresh weight were obtained by applying irrigation level 100% of IR, but the stem diameter and total dry weight were recorded by using irrigation level 75% of IR. The irrigation level 75% of IR significantly increased total and early yield during the two successive seasons. Regarding nitrogen form treatments, the highest vegetative growth was obtained by applying ammonium nitrate to the soil, followed by calcium nitrate. The interaction effect between irrigation levels and nitrogen forms was clear with the 100% irrigation level combined with ammonium nitrate giving the highest vegetative growth. Eggplant yield took another trend, the highest yield was obtained by using ammonium nitrate fertilizer under the irrigation level 75% of IR. Water use efficiency (WUE) had the same trend, applying 75% of IR gave the highest WUE values. Application of ammonium nitrate fertilizer led to increasing WUE compared to the other treatments during the two studied seasons.