Effects of different irrigation regimes and nitrogen levels on yield and quality of melon (Cucumis melo L.)

In order to study the effects of different irrigation regimes and nitrogen (N) levels on yield and some yield components of melon, a research was conducted at the Agricultural Experimental Field of the Harran University (Sanliurfa, Turkey) during the growth periods of 2007 and 2008. The growing season of melon was divided into four phenological stages: (i) Stage I, from seed germination to beginning of flowering; (ii) stage II; from beginning of flowering to small fruit, (iii) stage III; from small fruit to fullexpanded fruit and (iv) stage IV; from full-expanded fruit to harvesting. Regulated deficit irrigation (RDI), deficit irrigation (DI), full (I-full) and excessive irrigation (I-excessive) strategies were examined. The irrigation treatments were 33% (I0.33), 67% (I0.67), 100% (I1.00), and 133% (I1.33) ratios of total irrigation water applied (IW)/cumulative pan evaporation (CPE) with four day irrigation interval. Totally, 28 treatments were designed and applied as combination of nitrogen and irrigation levels. Four nitrogen treatments were: Control (N1), basic fertilizer (100 kg ha-1 pure N); N2, basic fertilizer + 30; N3, basic fertilizer + 60 and N4, basic fertilizer + 90 kg ha-1 as urea. The field experiment was setup employing a randomized split-plot design with three replications. N levels were assigned to the main plot and irrigation to the sub plot. Irrigation water amount applied, fruit yield and some quality parameters, yield response factor, irrigation water use efficiency, water use efficiency, water saving at different N levels and irrigation regimes were determined. Results show that irrigation regimes and N levels had significant effects on fruit yield. The best combination of treatments was N3*DI-low (T19) with a yield of 59.77 t ha-1 which corresponds to 10% yield loss providing 55% water saving. It could be applied for sustainable production, saving a significant amount of water and increasing the nitrogen use efficiency, where water is scarce.Key words: Melon, regulated deficit irrigation (RDI), nitrogen, yield