We demonstrated the practical utility of solar radiation mediated fertigation control for transplant production in a cell flat with an automatic ebb-and-flow fertigation system. Furthermore, we investigated seasonal changes in growth and productivity of stock (Matthiola incana R. Br.) cv. White Dorse as affected by fertigation frequency controlled in response to solar radiation (5 or 10 MJ · m^-2) and scheduled time course (once or twice per day).
The shoot dry weight of transplants and fresh weight of cut flowers were higher in plants fertigated with every 5 MJ · m^-2 of solar radiation, sown between late April and late July. In plants sown during other periods, there was no significant difference in growtn and productivity among plants fertigated differently. When the plants sown in June were fertigated twice per day, the exposure was 5 MJ · m^-2 in average of cumulatlve solar radiation from fertigation to subseauent fertigation. However, the maximum cumulative value exceeded 8 MJ · m^-2. Water stress caused by the high solar radiation accompanied by high temperature and large saturation deficit may have resulted in reduced growth of the transplants and decreased quality of the cut flowers.
When the stock transplants were grown in a cell flat (220 cells of 12ml cell volume), suffcient but not excess fertigation could be obtained by supplying nutrient solution every 5 MJ · m^-2 of solar radiation with an automatic ebb-and-flow fertigation system.