Managing of circulated nutrient solutions with saline water for pepper cultivation

The objective of this program is to optimize the greenhouse production of peppers by the use of circulating nutrient solution with local and desalinized water. The goal of the present study was to determine the effect of circulating untreated local water on pepper yield and to monitor the changes in the water salinity and mineral composition. Two salinity levels in the source water were tested -1.9 and 3.7 dS m(-1) - and the corresponding upper critical points for water replacement were set at 3.0 and 5.5 dS m(-1), respectively. Using the high-salinity water reduced the fruit yield significantly by 8.5%. This was less than the effect expected on the basis of the literature, and there was no influence on fruit physiological disorders. No effect on plant transpiration was detected. As the salinity of the solution increased, the Cl concentrations in all plant organs increased significantly, while nitrate concentrations decreased. The influence of the treatments on other mineral concentrations in plant organs was smaller and in most cases insignificant. The amounts of water that were displaced during 237 d of cultivation, in order to meet the critical set points for the low- and high-salinity treatments were 232 and 648, m(-2) (22 and 46% of the applied water), respectively. The salinity of the solution in the treatments irrigated with untreated water increased rapidly in spring and summer mainly because of increases in Cl, SO4, Na and Ca. Our future investigation will be focused on different mixtures of desalinized and untreated saline water, with different critical values of the salinity set point, for economic optimization of water resources management.