Investigation of quantitative and qualitative characteristics of Thomson navel orange on Citrumelo rootstock as affected by potassium and supplementary irrigation

The field experiment was conducted to study the effect of soil moisture tension and potassium on growth and quantitative and qualitative characteristics of Thomson navel orange on Citrumelo rootstock in Kotra Citrus research station in ten years (1998-2009). The experiment was designed for four replications in Randomized Complete Blocks with factorial treatment structure. The factors consisted of four levels irrigation (at 20, 40 and 60 Kpa of soil moisture tension and no irrigation) and four levels of potassium (0, 50, 100 and 150 gr multiplied by tree age). Potassium was mixed with soil and was applied under trees every year. Thomson navel orange (Citrus, sinensis (L.) osbeck) trees were irrigated by Micro jet irrigation system. According to the results, irrigation increased trunk diameter, plant height and canopy diameter and volume, yield, the number of fruits and TSS/TA. Potassium treatments increased soil exchangeable potassium, foliar K, fruit diameter, weight, peel thickness, acidity and total soluble solids and the ratio of peel thickness to fruit diameter. But, TSS/TA was decreased affected by K levels. Moreover, it did not affect plant growth parameters. Regarding yield and the number of fruits, interaction effects between potassium and irrigation rates were significant.