IMPACT OF CHEMICAL AND NATURAL WATER SAVING SOIL AMENDMENTS ON GROWTH, YIELD AND WATER USE EFFICIENCY OF ''WASHINGTON NAVEL'' ORANGE TREES UNDER DEFICIT IRRIGATION CONDITIONS

Abstract

Due to the limited water resources, it is necessary to study the best ways to reduce the use of irrigation water, increase the efficiency of water use without affecting the growth of trees and maintain the production of citrus productivity under these circumstances. Afield experiment was conducted during 2015 and 2016 seasons at El-Nubaria region, Beheira Governorate to investigate the effect of three irrigation water regimes (100, 75 and 50% of actual irrigation practiced in the orchard) and soil application of hydrogel (50 and 100g/tree) and organic plant residues (3.5 and 6.5kg/tree) as chemical and natural water absorbing soil amendments on growth, yield and water use efficiency on ''Washington Navel'' orange trees grown on a sandy soil under drip irrigation system. The obtained results point out that, applied organic plant residues at rate 6.5 kg/tree or 100g/tree hydrogel under moderate irrigation rate (T5 and T3) significantly increased the most growth parameters (canopy volume, number of shoots/branch and leaf area) , fruit set, leaf relative water content and decrease fruit drop%. Moderate irrigation rate + 100g/tree hydrogel (T3) and control (T1) were the best treatments in increasing leaf N,P,K and Ca contents. The highest yield (78.8 and78.47) and (80.36 and 79.06 kg/tree) was obtained by T3 and T5 in 2015 and 2016 seasons, respectively. All treatments increased water use efficiency especially T9 (5.64 and 5.46 kg/m3) compared with the control which recorded the lowest values (3.16 and 2.93 kg/m3). Control (T1) followed by T3 and T5 tended to improve the physical fruit properties meanwhile T8 and T9 increased the most of chemical fruit quality. The lowest fruit splitting% (6.58 and 5.87 %) coated with T3 and T5. Soil microorganisms content and dehydrogenase activity were increased under moderate irrigation rate + 3.5 or 6.5 organic plant residues (T4 and T5) compared to the control (T1).