Table 521

Maximum Tolerable Content of Cadmium for Soils Planned for the Production of Chamomile in Central Europe (According to Plescher [66], Cd Maximum Value for Matricariae flos 0.2 mg/kg)

pH Value of the Soil Max. Cd Content of the Soil in mg Cd/kg Soil, Dry Matter Spring Sowing Autumn Sowing

and flowering yarrow herb [67, 72]. As long as the maximum value of 0.2 mg Cd/kg of drug — a recommendation of the German Federal Ministry of Health since 1991 — is applicable, the maximum soil values indicated in Table 5.2.1 may be used for the choice of the location, depending on the individual pH value and on the method of cultivation [66]. If there are critical soil values a trial cultivation should always be used to determine whether the location is suitable.

5.2.2 Nutrient Supply

Although chamomile is a nitrogen-loving plant species, it is, in view of the harvest mechanization, seen that when cultivating it the soil only contains small amounts of Nmin and mostly it is done without any N-fertilization whatsoever [87]. Otherwise moist and leafy populations with a delayed flower maturity or "endless flowering" develop and with the application of harvest technique the species-typical appearance of foreign matter (percentage of leaves and stems) increases. Table 5.2.2 gives a general idea of recommendations for fertilization with respect to the cultivation of chamomile.

For the development of active principles, a good flowering, and sufficient firmness of stems, a good potassium supply is necessary [29]. On the other hand chamomile is delicate with regard to excessive quantities of P2O5. According to Franz and Kirsch [32] the nutrient ratio of nitrogen:potas-sium oxide should be 1:2. Fertilization by using potassium and if necessary also nitrogen takes place during the tillering phase, i.e., in October (at the Northern Hemisphere) or April (at the

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