Fruit yield and quality of drip-irrigated tomato under deficit irrigation

Abstract

The competition for limited amount of world fresh water is increasing at a fast rate. The agricultural sector is the major water user and also the most inefficient. As a result, the economic return from a unit of water is the lowest for agricultural sector. Therefore, in the wake of dwindling water availability, it is becoming imperative to look for ways of maximizing yield and quality of produce per unit of water. This is especially important in countries like Ethiopia, where there is severe water shortage in the arid and semi-arid areas. In this study, a field experiment was conducted at Melkassa Agricultural Research Center, Ethiopia to study the effects of moisture stress on the yield and quality of two tomato cultivars; Melka Shola and Melkassa Marglobe used as salad. The two tomato cultivars were exposed to four irrigation water deficit levels expressed as percentages of potential evapotranspiration (ETc) as: 0%ETc, 25%ETc, 50%ETc, and 75%ETc deficit. The total plant biomass decreased with stress level while the fruit dry matter increased. As a result, the harvest index (fruit dry matter weight/plant dry matter weight) was increased with stress level. At a given stress level, the harvest index of Melka Shola was higher than that of Melkassa Marglobe. Both the number and size of tomato fruits were found to decrease with moisture stress. The incidence of sun-scald and blossom end rot was higher in the more stressed plants (75%ETc) deficit. The total soluble solid (TSS) content was significantly affected by irrigation treatments. The total soluble content was increased with stress level while the fruit water content was decreased. The fruit total soluble content (TSS) of the stressed plants was also significantly different between the tomato cultivars. Melkassa Marglobe cultivar had higher total soluble solute content than Melka Shola cultivar. The higher total soluble solute content of Melkassa Marglobe might be the reason why this cultivar is preferred by consumers for use as a salad. It has been observed also that small animals and birds fed more on this cultivar than on the Melka Shola cultivar.