الفهرس 
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Abstract
A field experiment was conducted in new reclaimed areas during 2019–2020 growing season at Um-Saber Farm, plot 23, belongs to PICO “Modern agriculture company”, El-Boheira Governorate. This study aims to improve avocado trees water productivity cultivated under deficit irrigation as well as mulching. The sustained deficit irrigation (SDI) treatments were 90, 80, 70, and 60% of the reference evapotranspiration (ETo).
Results revealed that the water requirements during different avocado trees physiological growth stages were 613, 1509, 1755, 1391, and 632 m3/fed for flowering to end of fruit set, fruit set to approximately 50% of the expected market fruit size, during the fruit growth stage, during the fruit ripening stage, and during the flower bud formation stage, respectively. These values represent approximately 10.4%, 25.6%, 29.7%, 23.6%, and 10.7% of the total yearly water requirement.
The soil salinity (EC1:2.5) values slightly increased from 0.24 dS/m at 100 SDI-%ETo to 0.3, 0.4, and 0.54 dS/m at 90, 80, and 70 SDI-%ETo, respectively. Soil salinity increased to 1.04 dS/m when SDI reached to 60 SDI-%ETo. However, these increases in soil salinity occurred by increasing SDI levels up to 60 SDI-%ETo level, which had visible adverse effects on growth or production of avocado trees.
A slight increase in the concentration of K, Ca, Mg, Na, and Cl in soil due to the increase in SDI levels without any harmful effects on avocado growth or fruit production. There were significant increases in the accumulation of water-soluble K, Ca, Mg, Na, and Cl in soil for the treatment of 60 SDI-%ETo. These increases lead to impacts on growth and production of avocado trees based on known sensitivity to salts in growth medium.
There was only a slight increase in the content of K, Na, and Cl in avocado leaves, particularly at the 60 SDI-%ETo treatment. These results might due to the concentration effect from water stress associated with this level of SDI and the previously observed accumulation of these elements particularly between tree trunks.
The highest crop water productivity value of 1.24 kg/ m3 water was attained at 70 ETo-%ETo followed by 1.18 kg/ m3 water at 80 DSI-%ETo while the least CWP (1.06 kg/ m3 water) was realized at 100 %ETo. Hence the crop water requirement of 5110 m3/fed/year with high irrigation frequency is recommended for mulched sandy soil cultivated with avocado trees.