Irrigation Regime and Soil Conditioners Impact on Characteristics of Sandy Soil and Washington Navel Orange Trees

Abstract

Due to limited water resources it has become needed to study the best ways to decrease irrigation water use, increasing the water use efficiency, improve tree growth and sustain citrus crop production under those circumstances. Afield experiment was conducted during 2015/2016 and 2016/2017 seasons at El-Nubaria city, Beheira Governorate to investigate the effect of irrigation regime (80% and 60% from full irrigation) and soil conditioners (hydrogel at rate of 50 and 100g/tree as synthetic water absorbing soil amendments or organic plant residues at rate of 3.5 and 6.5kg/tree as natural absorbing soil amendments) on some properties of sandy soil, growth, yield, quality and productivity of irrigation water (PIW) for Washington navel orange trees under drip irrigation system. The obtained results pointed out that: The application of soil conditioners led to enhancing the properties and microorganisms activities and macronutrients of sandy soil especially with the high rates. Whereas, the low values of soil field capacity (10.47%), wilting point (4.26%) and available water (6.21%) were recorded with full irrigation without conditioners while, the high values (11.31 to 12.28%), (4.35 to 4.68%), (6.78 to 7.62%) respectively under irrigation regime combined conditioners. Soil conditioners application combined with irrigation regime increased the available nitrogen (up to 22.76%, phosphours (up to 9.98%), potassium (up to 15.14%), organic matter (up to 41.79%, CEC (up to 16.53%) and salinity (up to 4.64%) while soil bulk density was decreased (up to 5.66%) compared to full irrigation without conditioners. Moderate irrigation plus organic plant residues at rate of 6.5 kg/tree (T5) or plus hydrogel at 100g/tree (T3) significantly increased the most growth parameters (canopy volume, number of shoots/branch and leaf area), fruit set and decrease the fruit drop. Lowest percentage of fruit splitting (6.58 and 5.87 %) coated with T3 and T5 compared to deficit irrigation treatments plus the lowest rate of hydrogel or organic plant residues (T8 and T9). The highest yield was obtained by T3 (78.6 kg/tree) and T5 (79. 6 kg/tree). Control treatment (T1) followed by T3 and T5 tended to improve the physical fruit quality meanwhile deficit irrigation treatments T8 and T9 increased the most of chemical fruit quality. PIW mean values of Washington navel orange with full irrigation without conditioners were low (2.75 kg m-3) while, irrigation regime at 80 % and 60% recorded high…