ISHS Acta Horticulturae 548: International Symposium on Growing Media and Hydroponics
THE GRODAN WATER CONTENT METER FOR ROOT MANAGEMENT IN STONEWOOL |
| Author: | P. Stradiot |
| Keywords: | stonewool substrate, soilless culture, hydroponics, water content meter, root growth, root distribution, root development, substrate management, plant balance, tomato, sweet pepper, cultural methods, water content, electrical conductivity, irrigation management |
| Abstract:
The Water Content Meter (WCM) is able to measure in a stonewool substrate the water content, the electrical conductivity and the temperature. This instrument operates under the principles of frequency domain measurements. Since the roots are influenced by the above parameters, the management of the roots and thus also the plant can be monitored and steered by the WCM. In the rooting period (4-8 weeks after planting) the roots are ‘pushed’ into the slab by an alteration of wet and dry periods in the root zone. Over that period the slab water content (WC) drops also gradually, but the electrical conductivity (EC) has not to change. The totally rooted slab gives minimally 5% higher production. The reason for the more production is not yet scientifically proven but could be a bigger root buffer to overcome root stresses or a higher efficiency through cytokinin activities. The EC can be steered through the irrigation management. The parameters WC and EC can be steered independently. Long irrigations (>I50cc/dripper/irrigation cycle) will keep the EC in the slab more stable, or even will reduce the EC in the slab compared with short irrigations (<100 cc/dripper/irrigation cycle). The long irrigations go pair with a low frequency of the irrigation cycles so that the drain is kept stable. The difference between day and night water content in the slab steers the plant in a vegetative or generative way. A difference of less than 8% water content in the Grodan Master slab gives a vegetative action to the tomato plant. A difference of 10% and more give a generative stimulus to the plant. | |
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