EFFECT OF CONDUCTIVITY AND TEMPERATURE OF NUTRIENT SOLUTION ON THE MINERAL NUTRITION OF HORTICULTURAL CROPS IN WATER CULTURE

On a brief survey of grower’s nutrient solution on chemical analysis, we may conclude that electrical conductivity(EC) values cannot use a measure of nutrient levels for managing the culture solution.
In both rock-wool culture and Nutrient Film Technique(NFT) system,plants were not always making a healthful growth,owing to the ionic imbalance and depletion caused by rapid uptake of NO₃^– and K⁺ from the nutrient solution.
Additions of 1 g/lKNO₃ to the nutrient solution at weekly intervals were effective to keep an appropriate balance of nutrient solution and to promote the plant growth.

In the next, there was a close relationship between plant growth and root zone temperatures in the NFT system.
Dry matter production and the amount of mineral uptake were relatively high at 25°C for melon plants and 27°C for tomatoes by heating of the nutrient solution, though the minimum air temperature sometimes falls to 5°C at night in a plastic greenhouse in winter.
The content of protein-N,ratio of protein-N to total N,and dry matter production were increased with raising the root zone temperatures.
These results will readily suggest energy savings by keeping the greenhouse air temperature at lower than normal levels due to maintenance of the optimal root zone temperature.

Symposium on High Technology in Protected Cultivation

T. Takano

https://doi.org/10.17660/ActaHortic.1988.230.38