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Abstract
The importance of fertigation through drip irrigation system is increased by days. Technological blockages represented in equipment of acceptable performance and suitable quality prevents it to be used by small farmers. This study evaluates the effect of design and operating parameter on fertilizer injectors’ hydraulic performance. Also, it deals with both water and fertigation management for garlic as a vegetable crop. Three fertilizer injectors had investigated: by-bass pressurized mixing tank (J1), venturi(J2), and positive displacement pump (J3). Three irrigation rates were used 50, 75, and 100 % ETc (I1, I2; I3), and three levels of N- fertilizer (NH4)2SO4 namely 60, 90, and 120 kg/fed (N1, N2; N3). The results show that, the best injection rates were 40, 3.0, and 240.2 l/min under pressure differences of 0.7, 1.4, and 2.5 bar for by-bass pressurized mixing tank, venturi, and positive displacement pump, respectively. Two dimensionless coefficients were driven CQ (Coefficient of injection rate) and CP (Coefficient of pressure difference) for different parameters affect injectors’ performance. The dimensionless coefficients showed increasing degradation in performance for venturi, by-bass pressurized mixing tank, and positive displacement pump. The maximum values of CQ were 2.3 × 103, 3.06 × 104, and 18.4 × 104 at CP values 3.9 × 105, 1.95 × 105, and 7 × 105, respectively. The emitter clogging percentage was measured for the drip irrigation system at the end of garlic growing season 2006 / 2007. The maximum and minimum values of clogging percent were (17.79, 22.8; 27.9) and (13.24, 15.81; 18.9) under the condition of (J3, J2; J1), (I1 × N3) and (I3 × N1), respectively. The highest garlic yield (6.26 ton/ fed.) was obtained in treatment (J3 × I2 ×N3). Maximum value of water use efficiency (WUE) was 3.289 kg garlic / m3 of irrigation water was recorded in the treatment J3 I1 N3, while the minimum one was 1.3 kg garlic / m3 of irrigation water recorded in the treatment ( J1× I3× N1). The maximum value of nitrogen use efficiency (NUE) in kg garlic/ kg N was 83.5 and the minimum one was 29.7 in interactions (J2 ×I2×N1) and (J1×I1 ×N3), respectively. The maximum value of net profit was (4520.69 LE/ fed.) as recorded in the treatment J3× I2 ×N2 (Positive displacement pump, 75% of ETc and 90 kg N /fed) while the minimum value was (708.942 LE/fed.) as recorded in the treatment (J1× I3× N1). The interaction J3× I2× N2 (Positive displacement pump, 75% of ETc and 90 kg N /fed) increased the net profit by 57.61% in addition to saving 25% of irrigation water and 33.33 % of nitrogen fertilizer compared to the interaction (J3× I3 ×N3).