Articles
PRACTICAL PLANT NUTRITION IN GLASSHOUSES IN DENMARK
For many years we have used soil-analyses as a good guide for plant nutrition.
We also have years of experience with the use of plant analyses in relation to plant nutrition.
During the late part of the sixtees and in the beginning of the seventees there was an increasing interest in growing in other materials than soil.
The high costs of energi used in steaming of soil caused a dramatic change in the choice of growth medias.
At about the same time the rock-wool growing system was introduced and this ment that the need for more knowledge about intensive plant nutrition became more pronounced.
Only a few people had experience with growing plants in inactive medias, such as rock-wool, gravels etc.
Nearly at the same time the Nutrient Film Technique (NFT) was introduced as a system for growing plants in circulating water culture.
Both the rockwool-system and the NFT demanded a very good knowledge in plant nutrition.
This interest for growing in NFT or water culture was the reason for setting up a Danish working group for water culture.
The group was set up in october 1974 and consisted of members from the advisery service and from the experimental station and the agricultural university.
The work in the group resulted first of all in the development of a model for plant nutrition which could be used in practical glasshouse nurseries.
The working group started up with lettuce as an experimental plant.
Lettuce is normally grown on soil but there was some interest in finding new possibilities for a more rapid turnover, and for a better utilization of the glasshouse area.
It should also be possible to obtain a better keeping quality of the lettuce.
The lettuce plant also has the advantage of being grown only in its vegetative stage, which means that it is easier to work with, when looking at nutritional problems.
Later on, we used tomato as an example of a plant, which has a different requirement to the nutrient solution.
This would mean, that one must change the nutrient program as the plant change from vegetative to generative development.
The investigations in lettuce resulted in development of a practical growing system and a nutritional method by which the growers could grow the crop in a water culture system.