A SOILLESS EBB-AND-FLOW SYSTEM FOR ALL-YEAR-ROUND CHRYSANTHEMUMS

We developed a closed cultivation system with ebb-and-flow irrigation for chrysanthemums, in which only 15 cm³ of substrate per plant is used in the form of a small, fibrous plug. A series of experiments was conducted, aimed at optimization of production factors in the root-zone, i.e. mineral nutrition, irrigation frequency and root aeration. Nutrient uptake was efficient, as shown by influx concentrations for N and K, which were considerably higher than concentrations in the bulk nutrient solution. There was little difference between four ebb-and flow treatments in production or mineral nutrition, but severe waterlogging symptoms developed in completely stagnant nutrient solution culture. In over 2 years of experimentation, it was possible to produce chrysanthemums of a constant good quality, and the system showed a high productivity. Although no chemical or physical sterilization was applied, no problems with root diseases were encountered. The high productivity indicates that the ebb-and flow system may have advantages over soil-based cultivation. However, it is still uncertain whether these advantages are large enough to make the system economically competitive.