EVALUATING THE EFFECTS OF DRIP DEFICIT IRRIGATION AND THICKNESS OF RICE STRAW MULCH LAYER ON BEANS CROP AND WATER USE EFFICIENCY

Two field experiments were conducted during the two growing seasons (2014 and 2015) to investigate the combined effects of three irrigation treatments (I100% =100%, I85% =85% and I70% = 70% of crop evapotranspiration (ETc)and four thicknesses of mulch layer (TML0, 3, 6 and 9 cm) under drip irrigation system. The Results showed that the irrigation treatments and thickness of mulch layer on yield and WUE were significant. The greatest values of bean yield (902.4and 909.6 kg fed^-1) were obtained under (I100%) in the first and second seasons, respectively, while the lowest ones (698.1 and 692.5 kgfed^-1) were obtained from treatment (I70%) in the first and second seasons, respectively. The average bean yield value of TML9 was increased by 11.5, 30.8 and 40.2 % than those of treatment TML6, 3 and 0, respectively, in the first season. Corresponding values for the second season were 12.3, 32.5 and 43.5 % The greatest values of WUE (0.74 and 0.73 kg m^−3) were obtained under I70% compared to I100%, (0.67 kg m^−3) in the two seasons, respectively. The interacting effects between treatment I100 and treatment TML9 i.e. (I100× TML9) has proved, to be the most suitable for producing high bean crop. Under environmental condition of the studied area. Application of (I85×TML9) treatment was found to be favorable to save 15% of the applied irrigation water, with no decrease in bean crop yield.