F. Penningsfeld
Since 1967 we have been conducting comprehensive experiments on the nutrient requirements of pot plants at Weihenstephan. To eliminate any disturbing influence from the soil on plant growth, a mixture of peat and styromull in a volume ration of 1:1 was used. This same substrate had previously served in research with cutflowers of which a report was given in copy no. 18 of 'Acta Horticulturae' page 53–65. Styromull is a plastic foam based on polystyrol and acts only as thinner as it does not release, store or absorb any nutrients from the soil. The minimum content of nutrients in high moor peat is reduced even further which soon leads to nutrient deficiency and allows for easier observation of plant reaction. Salts free from micro-elements were used for fertilization. The plants were cultivated in plastic pots placed on plastic saucers to prevent nutrient loss through leaching and were irrigated with water purified by ion exchange.

In addition to a control row in which lime as well as macro and micro elements were added in good proportions, further variants were included in each of which either a macro or micro element was eliminated or given in double strength. Also an unfertilised row was included in order to test the nutrient content of soil and plant material. This resulted in 25 variants with 24 or 30 plants in each (table 1). In setting these up in 3 or 4 groups, the differences in plant development could be calculated by analysis of variance.

The plants tested in the experiments were Fuchsia hybrida "Beacon", Chrysanthemum indicum "Yellow Delaware", Rhipsalidopsis gaertneri and Primula obconica "Bayernblut". In table 2 the amount of lime and fertilizer added to the control rows is listed.

The data in table 2 refer to one plant or the content of one pot respectively. The amount of fertilizer given in the control row was based on previous experiments. It was varied according to plant requirements. However, an equal amount of micro elements and lime was added, if not stated otherwise in the experiment lay-out. To evaluate the experiments, observations, measurements, countings, weighings and numerous analyses were carried out. A report of the results obtained follows.

Penningsfeld, F. (1972). MACRO AND MICRO NUTRIENT REQUIREMENTS OF POT PLANTS IN PEAT. Acta Hortic. 26, 81-102
DOI: 10.17660/ActaHortic.1972.26.11

Acta Horticulturae