*1Nooruldeen S. Ali and 2Qais H. A. Al-Semmak
Field experiment was conducted in sandy soil at a cultivated desert between Karbala and Najaf Governorates to investigate different sources and rates of potassium fertilizers application on water and fertilizer productivity of maize. The experiment was a randomized complete blocks design with three replicates. Treatments included two sources of potassium fertilizers (potassium sulfate and potassium chloride) and four levels of each fertilizer (0, 75,150 and 300 kg K ha-1 ). The applied amounts were divided into six segments added through fertigation. Maize (Corn) "Zea mays L." was planted in summer 2005 and was irrigated through drip irrigation. Results of the experiment indicated that levels of applied K increased plant K content especially with 150 kg K ha-1 . The highest values of potassium use efficiency (KUE) were obtained with 150 kg K ha-1 . Grain yield increased with potassium application with 150 kg ha-1 giving the highest yield 4.90 Mg ha-1 at 150 kg ha-1 with an increment of 56% compared to controlled treatment but with no significant differences than 75 kg K ha-1 . The highest value of fertilizer productivity was obtained with 75 kg K ha-1 . Potassium levels applied increased Water productivity giving a value of 0.54 kg m-3 at 150 kg K ha -1 compared to 0.349 kg m-3 at controlled treatment. Therefore, it can be concluded that 75-150 kg K ha-1 can give good results under such conditions.
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