Effects of water stress applied with sub-surface drip irrigation on forage productivity and water use efficiency of alfalfa under precise irrigation practice in arid climate.

A field experiment studied the effect of water stress on alfalfa productivity and water use efficiency was conducted at the Agricultural Experimental Station of King Abdul-Aziz University. The design of the experiment was Randomized Complete Block Design (RCBD) with four replicates, consists of three treatments namely: field capacity treatment (FC) as a control, 85% FC and 70% FC as stress treatments. The irrigation water for all treatments was precisely supplied using Water Electronics Module (WEM). The results indicated that, decreasing water supply decreased fresh and dry yield of alfalfa however it increases IWUE indicating more efficient use of water by the crop and consequentially increasing water saving. 13% and 27% of irrigation water can be saved from 85% FC and 70% FC in each cut when it compared with FC treatment. The reduction of water supply resulted in yield reduction by 12% and 21.7% for 85% FC and 70% FC, respectively. The results also proved that WEM is a practical tool to precisely supplied irrigation water and can be use effectively to control deficit irrigation. Key wards: Sub-surface Drip Irrigation, Precise Irrigation, Alfalfa, Deficit Irrigation.