Judul: Development of Water Stress Treatment System for Long-term High Brix Tomato Production in Hydroponic Culture
Abstrak: Nowadays, the demand of high brix tomato as known as fruit tomato is increased. Many studies found that water stress treatment can be used for the production of high brix tomato, however, these are obtained for short-term experiment in water content around 50%-80% (Nuruddin et al. 2003; Patane and Consentino, 2010). The effect of water stress treatment on plant growth is well known, but how to operate the water stress treatment to increase the quality of tomato fruits is not known very well. It is not easy to grow health plant in water stress condition. This research introduces visual monitoring system to control severe water stress condition. The objectives of the present study are to develop a water stress treatment system for long-term high brix tomato production in hydroponic culture and evaluate the performance of water stress treatment system in long-term severe water condition with seasonal change on the quantity and quality of tomato fruits. Furthermore, the effect of water stress on plants growth was examined. All data that from this research could be used for database of development of water stress treatment system on tomato plants. Tomato (Solanum lycoperscium L., Momotaro Sakura) plants were grown hydroponically on rock wool slabs in a greenhouse in Faculty of Agriculture, Ehime University. Water stress treatment was applied at 14 weeks after transplanting. Leaf area was monitored by digital camera that pictures were captured every 15 minutes. The water content of the slabs was measured by Water Content Meter once a day at noon. There are two treatments in this research, water stress treatment and control. The water content of slab was maintained around 20%-30% for water stress treatment and 60%-70% for control, which was controlled base on the projected leaf area and water content of slabs. When the projected leaf area was decreased fewer or less than 95% of the maximum projected leaf area which was measured after the last irrigation and the water content of the slab was fewer than 20%, the nutrient solution was supplied to the plant until recovering to 20%. For the growth rate measurement, stem diameter and elongation were measured once a week by caliper and measuring tape, respectively. Fruit diameter, sweetness, and sourness were measured by ISEKI grading machine. The calibrations for sweetness were conducted by destructive method with Refractometer, while the sourness was calibrated by KUBOTA Fruits Selector machine. The results indicated that it took 1.5 hours from full unfuried condition to full recover. Some irregular situations were observed when solar radiation was high and relative humidity was low, water content was around 11% that was lower than the expectation. On the other hand, when solar radiation was low and relative humidity was high, water content was around 40% that was not expected. Low solar radiation and high relative humidity can be contributed to maintain the water content at high level. Stem diameter was 4.4 mm-7.78 mm for water stress and 8.45 mm-11.68 mm for control. Stem elongation rate was 0.08 m week-1-0.18 m week-1 for water stress and 0.17 m week-1-0.25 m week-1 for control. Both
Keyword: high technology greenhouse, irrigation control, high brix tomato, water stress