THE GROWTH, YIELD AND QUALITY OF GREENHOUSE TOMATOES IN RELATION TO SALINITY APPLIED AT DIFFERENT STAGES OF PLANT GROWTH

Abstract

Four levels of salinity in the irrigation water (I: 1.7dS/m (control), II: 3.7dS/m, III: 5.7dS/m and IV: 8.7dS/m) were applied to tomato plants at various stages of growth and for different time duration. Treatment A was irrigated with the four different concentrations for the last 75% of the duration of the experiment, treatment B for the last 50%, treatment C for the first 50% and treatment D for the whole experimental period, which was 79 days. Salinity negatively affects the size of the plant and total weight of fruits: the higher the concentration, the lower the growth and yield. In comparison with the control, there was a 20.3%, 30.2% and 49.0% reduction in yield and 2.9%, 12.2% and 20.1% in the height of plants, for the three concentrations (3.7, 5.7 and 8.7dS/m) respectively. By contrast, the number of fruits produced was significantly reduced only at highest level of salinity (8.7dS/m). The average weight of fruit was reduced at the highest salinity especially when applied at an early stage of growth. When the salinity stress was applied during the entire growing period the negative results were higher, with increasing reduction in yield occurring with the increase in salt concentration. When good quality water was applied at the beginning of growth, followed later by salinity, the negative effect on plant height, fresh and dry weight of shoots, leaf area, yield, average weight of fruits and the percentage of fruit with blossom-end-rot was less severe. By contrast, when saline water was applied at the early stages of growth, followed by good quality water, the effect on plant parameters (total yield, average weight of fruits and blossom-end-rot) was more severe. The longer the duration of saline application was, the more severe the reduction in leaf area was compared with the control. Increased salinity (various concentrations) increased soluble solids, Na, K, Cl contents of the fruits, irrespective of the time of application.