Articles
GROWTH REGULATION OF BEDDING PLANTS AND POINSETTIA USING LOW PHOSPHORUS FERTILIZATION AND EBB-AND FLOW IRRIGATION
P treatments applied in the nutrient solutions varied from 0.02 up to 1.2 mmol/l H2PO4. It was established that to obtain any effects of P, stock fertilizer should not be incorporated in the potting soil.
General effects of P stress were lower fresh weights and plant heights.
Other effects depended on the plant species involved.
In Pelargonium, the number of side shoots and flowers were reduced by P stress.
In Petunia, the number of buds was decreased at the most extreme P stress treatments.
In Salvia, the number of lateral side shoots and flowers was reduced, whereas the number of internodes was not affected.
In Impatiens, plant width and the number of internodes were reduced by P stress.
However, number of flowers and number of shoots were not influenced.
The results imply that for Impatiens, a positive plant appearance without the use of any chemical growth regulators is possible.
In Poinsettia, the number of branches and leaves were reduced by P stress.
Furthermore, probably due to reallocation of P, the senescence of old leaves increased.
It is concluded that P-fertilization can be reduced, under commercial growth conditions, without great negative side-effects.