Tomatoes (Lycopersicon esculentum Mill. cv. Sunstart) were grown in a greenhouse during Summer 1999 and again in Winter 2000. Two available soil water (ASW) deficit thresholds, 65% and 80%, at which plants were irrigated to field capacity were factorially combined with five irrigation timing patterns: 1) no water stress; 2) stress throughout the entire growing season; 3) stress during first cluster flowering and fruit set 4) stress during first cluster fruit growth; and 5) stress during first cluster fruit ripening. Crop yields, water use efficiency, as well as maximum and minimum equatorial fruit diameters and fruit height were measured. Quality parameters of soluble solids, pH, and fruit color were also measured. Water stress throughout the growing season significantly reduced yield and fruit size, but plants stressed only during flowering showed fewer but bigger fruit than completely non-stressed plants. Consequently, on a weight basis the stressed at flowering and nonstressed plants had similar yields. Nonstressed and flowering-stressed fruit showed lower soluble solids and a lighter color of red ripe fruit than the other stress treatments. No significant differences in yield or quality were found between the two stress levels (65% vs. 80% ASW depletion before irrigation). Water stress only during flowering resulted in better yields and quality than stress at other specific developmental stages or at all times, but equal or poorer yields and water use efficiency than nonstressed plants.
Molla Md. Nuruddin, Chandra A. Madramootoo and Georges T. Dodds
Georges T. Dodds, Leif Trenholm and Chandra A. Madramootoo
In a 2-year study (1993-1994), `New Yorker' tomato (Lycopersicon esculentum Mill.) plants grown in field lysimeters were subjected to four watertable depth (WTD) treatments (0.3, 0.6, 0.8, and 1.0 m from the soil surface) factorially combined with 5 potassium/calcium fertilization combinations. Mature-green fruit from four replicates of each treatment were stored at 5C for 21 days, and fruit color was monitored with a tristimulus colorimeter. Fruit were subsequently allowed to ripen at 20C for 10 days, at which time chilling injury was assessed on the basis of delayed ripening and area of lesions. Potassium and calcium applied in the field had no effect on chilling tolerance of the fruit. In the drier year (1993), shallower WTD treatments generally yielded fruit that changed color less during chilling and were more chilling-sensitive based on delayed ripening. In the wetter year, differences in color change and chilling tolerance between WTD, if any, were small. Over both years, lesion area varied with WTD, but not in a consistent manner. Based on these results, we suggest that differences in water availability should be considered when studying tomato fruit chilling.
Georges T. Dodds, Leif Trenholm, Ali Rajabipour, Chandra A. Madramootoo and Eric R. Norris
In a 2-year study (1993-94), tomato (Lycopersicon esculentum Mill. `New Yorker') plants grown in a sandy loam soil in field lysimeters were subjected to four water table depth (WTD) treatments (0.3, 0.6, 0.8, and 1.0 m from the soil surface). In 1994, precipitation during the flowering stage was far above average and apparently led to waterlogging in the shallowest WTD treatment, while in the drier year (1993), the deepest WTD treatment suffered from drought stress. In general, over the 2 years, the 0.6-m WTD showed the best yields and largest fruit, while the 1.0-m WTD showed the lowest yields and smallest fruit. However, the incidence of catfacing, cracking, and sunscald was generally higher in the 0.6 m WTD treatment and lower in the 1.0-m WTD treatment. Furthermore, fruit firmness was generally greatest for the two deeper WTD than for the shallower WTD. To strike a balance between yield and quality, a WTD of between 0.6- and 0.8-m is recommended for tomato production on sandy loam soils.