Effects of short duration partial rootzone drying (PRD) on soilless grown tomato crop

We have studied partial rootzone drying (PRD), on soilless grown greenhouse tomato. The tomato plants were grown hydroponically during 253 days of period from September to June in greenhouse in Mediterranean climate. Four treatments were used in the experiment: (1) Full-open irrigation and (2) full-close irrigation, where all roots under both treatments were wetted in every irrigation, (3) PRD open and (4) PRD close treatments where 30 to 50% reduced nutrient solution was applied compared to full irrigation treatments. Under the PRD treatments, the plant root system was separated to two parts and the root zone were interchanged every irrigation in subsequent irrigations during the day. In the open systems the excess irrigation or nutrient solution was discharged as drainage from the greenhouse. In the close systems drainage effluent from the base of the growth containers was collected, re-cycled and therefore re-used in the system. Irrigation frequency during the experiment was changed between 4 to 20 times, every hour or every 45 minutes from 6.00 am to 20.00 pm, per day depending on plant age and climatic conditions. There was no adverse effect of PRD on both plant growth and yield in soilless grown greenhouse tomato. The reason may be the frequent interval of the wetting and drying cycles of plant rootzone in soilless practice. The interval of changing the irrigated halves of the root zone may be as short as hours or even minutes. The soilless growing systems give better benefits to the plants to manipulate physiological responses in more proper conditions than in PRD soil application. The results additionally showed that the nutrient solution use efficiency was highest in "PRD-Close" due to saving of nutrient solution by the combined effects of deficit irrigation with PRD and re-cycling of nutrient solution. As conclusion the PRD applications in soilless grown greenhouse crops have good potential for saving water and nutrient solution as well as its environment friendly nature with minimized drainage discharge