EFFECT OF WATER SALINITY AND POTASSIUM FERTILIZER LEVELS ON TOMATO PRODUCTIVITY AND WATER CONSUMPTION IN SIWA OASIS

Abstract

Effects of four irrigation water salinities; ECiw (1.25, 2.5, 5 and 10 dS/m) and four potassium fertilizer levels; K + (0, 40, 80 and 120 kg K2O/fed) on yield and some quality parameters and water consumptive use; WCU of tomato grown under Siwa Oasis conditions were investigated. The splitplots design was carried out during the two successive growing seasons of 2003/04 and 2004/05. Yield, some quality parameters, water consumptive use and soil salinity data were inspected and subjected to proper statistical analysis and Maas and Hoffman threshold model. Water use efficiencies were also quantified. Results indicated that, the maximum total and marketable yield of 17.5 and 14.76 Mg/fed, respectively was associated with the control treatment (ECiw= 1.25 dS/m). Increasing the ECiw, resulted in reducing the fruit number per plant, smaller fruit size and weight and consequently decreasing the total and marketable yield, increasing the fruits affected with blossom end rot (BER), higher total soluble solid content and decreasing the pH of the fruit juice were recorded. Increasing the ECiw led to decreasing both of water consumptive use and water use efficiencies. While, under moderate ECiw and high level of K+ enhanced the plant growth parameters, total and marketable yield and water consumptive use and reduced the fruits affected with BER. However, the effect of the ECiw on the tested parameters was more pronounced than the effect of the K+ . The decrease of the total and marketable yield was performed to linear slope of 11.14 and 14.69 % per dS/m after the recorded threshold (ECt) value of 2.97 and 3.31 dS/m, respectively. The decrease of tomato fruit yield with salinity was mostly owing to a linear decrease of the fruit weight of 9.8% per dS/m. Reduction of the fruit number with salinity of 5.5% per dS/m made small contribution to reduced yield.