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