Silber, A., Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel

The general objective of the present research was to explore the effects of combined irrigation and fertilization (fertigation) frequency on growth, yield and uptake of water and nutritional elements by plants. Soilless grown bell pepper was used as a model plant. Special attention was given to the effects of fertigation frequency and P application rate on blossom-end rot incidence in bell pepper (Capsicum annuum L., cv. Selika) grown in soilless culture. The experiment comprised six treatments: two concentrations of phosphorus (3 and 30 mg L-1) combined with three fertigation frequencies (two and eight events per day and for 1.5 min every 25 min which is 30 applications throughout the day). Increasing the fertigation frequency significantly increased the plants' acquisition of nutrients, especially phosphorus and manganese. A significant linear regression was obtained between aboveground biomass, and leaf P concentration in the early vegetative stage. Based on the linear regression, 96% of the dry weight variations could be explained by differences in leaf P concentration, indicating that the main effect of fertigation frequency was related to improved P mobilization and uptake. Increasing the daily fertigation frequency from two to eight and to 30 applications reduced the number of blossom-end rot fruits from 7 to 3 and to 2 per plant, respectively, and accordingly, increased the yield of export-quality fruits from 6.5 to 10 and to 10.5 per plant, respectively.