Effect of some Drip Irrigation and Nano-Silicon Treatments on Growth, Yield and Water Relations of ''Washington Navel'' Orange Trees Grown in New Reclaimed Soils

Abstract

The deficiency of irrigation water is a main factor of limiting the growth and production of fruit trees, particularly in arid and semi-arid areas regions. So this study was conducted in order to assess the influence of applying silicon in the nano form to minimize the negative effects caused by water stress. A field trial was behaved in 2016 and 2017 seasons at Beheira Governorate to study the effect of three rates of drip irrigation viz.high irrigation rate (control=100%) and two deficit irrigation regimes (75 and 50% from the control), foliar application of nano- silicon (0, 100, 200 and 300ppm) and their interaction on growth, yield and water relations of ''Washington Navel'' orange trees grown in sandy soil and irrigated by drip irrigation method. The findings showed that, deficit irrigation treatment (I3) was related with reduced vegetative growth aspects (canopy volume, No. of shoots /branch, Shoot length) as well as stomatal resistance, however transpiration rate was increased in both seasons, in addition, nano-silicon spraying at 300 or 200ppm caused a significant increase in previous growth aspects over the control.The combination between high or moderate irrigation rate (I1 or I2) with nano-silicon spray at 300 ppm (S4) were more effective in enhancing growth parameters. In both seasons, deficit irrigation treatment (I1) decreased leaf mineral contents and increased leaf proline content. However, high concentration of nano-silicon markedly increased leaf mineral contents but reduced leaf proline contents. Both low and high irrigation rates (I2 and I3) or high concentration of nano-silicon (S4) and their interaction achieved the highest values of bound water and osmotic pressure and the lowest values of total and free water contents. Furthermore, the yield and components, water use efficiency and most of external and internal fruit properties were significantly increased under moderate irrigation (I2) or high concentration of nano-silicon and their interaction (I2 xS4), while, the percentage of fruit splitting was decreased. Finally, trees irrigated with moderate irrigation rate combined with nano-silicon at (300 ppm) enhancement the growth, yield and fruit properties. On the contrary decreased fruit splitting(%) and applied irrigation water by 25% , whereas, increased water use efficiency compared to high irrigation rate (control) without nano-silicon spray.