[Proof of soil sickness in growing apple plantations (author's transl)].

1. Soils from five apple orchards of different age and from different sites were tested with respect to the occurrence of soil sickness. 2. Severe or very severe soil sickness could be proved in four of the sites. In one site weak soil sickness could be obtained. 3. These results confirm earlier observations on the occurrence of soil sickness within the regions of growing root systems of older trees. 4. The occurrence of soil sickness in growing plantations can be brought in good correspondence with the ascertainment that microorganisms associated with roots are to be considered as the cause of soil sickness. 5. The significance of the occurrence of soil sickness in growing plantations for development and yield of trees must be investigated in further experiments.