Articles
THE USE OF SLOW RELEASE FERTILIZERS IN POT PLANT PRODUCTION
IBH gave the best yields and the most regular N-supply during a period of up to five months.
Only in pure peat (pH 4, 2) its initial N-release was too high which caused growth depressions.
On the basis of these trials a slow release fertilizer was formulated; its components are IBH, Magamp, potassium sulphate, and trace elements (N:P:K = 14-7-14). It is now manufactured in Switzerland by Hauert AG, Grossaffoltern, and quite widely used.
It was named "Tardit 212".
In 1974 six commercially available slow release fertilizers were compared:
| Tardit 212 | – Hauert, Switzerland |
| Triabon | – BASF, Germany |
| Plantosan | – 4D, Philips Duphar, Germany |
| Osmocote | – Sierra Chemicals, USA |
| Organos | – Geistlich, Switserland |
| Ionoterr | – Bayer, Germany |
The trials were carried out in five nurseries with "Riegers" Begonia, Chrysanthemums and Poinsettia.
The amounts of the fertilizers were calculated to the same amounts of nitrogen.
In each trial the control plants were treated with repeated liquid fertilizing according to the standard method of each nursery.
Triabon, Tardit 212 and Organos gave the best results.
The optimal N-amounts were 400 to 500 mg N/lt for Begonia and Poinsettia, 600 to 800 mg N/lt for Chrysanthemums.
Initial growth depressions due to a surplus of N were occasionally observed with Tardit 212, rarely with Triabon.
These depressions disappeared normally after four to five weeks.
At the end of the growing period one or two additional liquid fertilizings were sometimes necessary to obtain the same qualities as with standard fertilizing methods.
Plantosan 4D in a finer and a coarser granulation was very compatible but lasted only five to six weeks; liquid fertilization during the second half of the growing period was indispensible.
Osmocote (18-9-13) started too slowly; it lasted longer than the other fertilizers, but the initial backlog in growth was rarely made up for.
Ionoterr was difficult to compare with the other fertilizers as its nutrient content was not exactly known; it was very compatible but its period of release was much too short.