الفهرس 
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Abstract
Two field experiments were carried out at the Agricultural Experimental Station, Mansoura Univ., during the two successive growing seasons of 1998/99 and 1999/2000 to evaluate the effect of soil moisture depletion, applied N, P and K fertilizers either by fertigation or by side dressing method and their interactions on water consumptive use, water use efficiency, plant growth, yield and yield components, quality and mineral composition of potato plants under drip irrigation system in an alluvial soil of North Delta region. In the 1st season, two levels of soil moisture depletion (25 % and 50 % of ASMD) assigned to the main plots and four levels of fertigation (Zero, 25 %, 50 % and 75 % of NK requirements) occupied the subplots, while the subsub plots were assigned to the different combination of 3 nitrogen levels (Zero, 75 and 150 kg N fed1) which were added as ammonium nitrate 33.5 % N and three potassium levels (Zero, 50 and 100 kg K2O fed1) which were added as potassium sulfate 48 % K2O. While in the 2nd season, the main plots were occupied by the aforementioned levels of ASMD in the 1st season, meanwhile the subplots were assigned to the three fertigation levels (Zero, 50 % and 100 % of NPK requirements) and the subsub plots were splited into the different combinations of 3 nitrogen levels (Zero, 50 and 100 kg N fed1) which were added as ammonium nitrate by soil addition and diamonium phosphate (DAP, 18 % N and 43 % P2O5) added through drip irrigation system, two P levels (zero and 75 kg P2O5 fed1 as diamonium phosphate and two K levels (Zero and 100 kg K2O fed1 as potassium sulphate 48 % K2O. At the end of fertilization programme, a random sample of 6 plants from each treatment was chosen after 110 days from planting to study the differential responses of plant growth characteristics, yield and yield components, tuber quality determinations and mineral composition water consumptive use , water consumptive use efficiency of drip irrigated potato plants. The obtained results show that, the possibility of producing high and good tuber yields of potato plants in the alluvial soil conditions of North Delta region at 25% soil moisture depletion by using fertigation method with the rate of 150 N + 75 P2O5 + 100 K2O kg fed1 under drip irrigation system.