ISHS Acta Horticulturae 98: Symposium on Research on Recirculating Water Culture
PH OF THE FLOWING NUTRIENT SOLUTION |
| Author: | J. Willumsen |
| Abstract:
In water culture, the pH of the flowing nutrient solution must be controlled and adjusted regularly. For 230, 189, and 147 days tomato plants were grown under glasshouse conditions in recirculating solutions with pH levels of 4.5, 5.5, and 6.5. Demineralized water was applied. The pH levels were maintained throughout the growing periods by daily adjustments of the ratio between the concentrations of NH4-N and NO3-N in the recirculating solutions. This method for adjusting the pH was compared to that of acid addition. The differences in pH levels did not directly affect the tomato yield. The adjustments of the pH level 4.5, however, required addition of so much NH4-N that the proportion of 1st class fruits was reduced, possibly owing to Ca or Mg deficiency in the plants, although the solution was not deficient in Ca and Mg. The reason may also be deficiency of K or P. Relative consumption (N=100) of macronutrients was calculated for the vegetative and the vegetative-generative growing periods. These data, showing the relative amounts of macronutrients which disappeared from the recirculating solutions, constitute a more correct basis for composition of supplementary solutions than the corresponding plant analyses. | |
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