CONTROL OF WATER AND NUTRIENT SUPPLY IN GREENHOUSE VEGETABLE PRODUCTION BY MEANS OF HYDROPONIC SYSTEMS

In the interest of an economical nutrient consumption and low environmental stress the surplus nutrient solution in open hydroponic systems such as substrate culture with rockwool has to be minimized.
Experiments have been started to compare three different control principles with tomatoes:

1. Control based on a simple model of water consumption

2. Control based on stem thickness

3. Control based on the amount of drain water

The technical equipment applied and control algorithms have been described.
Comparing the first results the third control principle seems to be the best one allowing the surplus nutrient solution to be reduced to 5 to 10 %. Advantages and disadvantages have been discussed.
Notwithstanding the obtained results, long-term orientation must be directed to closed hydroponic systems.

International Symposium on Growth and Yield Control in Vegetable Production

F. Güohler, A. Heiβner, H. Schmeil

https://doi.org/10.17660/ActaHortic.1989.260.13