Die Wirkung einiger Biozide auf die Bodenmüdigkeit bei Apfel und auf die Mikroflora müder Böden

Abstract

Summary Many plant species being cultivated one after another immediately or too quickly show growth and yield reductions which are called replant damages. Besides the accumulation of known pathogens still unknown causes are made responsible for this phenomenon. Only the last are to adjoin to the term soil sickness. Among the replant damages with apples soil sickness cuts a special figure. It is characterized by a high peristence in the soil even after a short-term apple cultivation. Therefore it cannot be overcome by realizable cultivation stops. From own investigations the hypothesis was derived that soil sickness is caused by soil actinomycetes. These organisms penetrate into the fibrous roots, colonize and damage them so that the roots die off. This process results in an enrichment of the actinomycetes in the soil. Investigations about the suitability of different biocides for the control of soil sickness led to the result that some of them posess marked actinomycidic properties when added to microbial culture media. These cannot be proved when they were added to soil. In accordance with this observation there is to observe no activity against soil sickness. Other biocides with pronounced actinomycidic properties in agar media and a low activity in soil don't influence the growth of apple seedlings in sick soil too. Only biocides with high actinomycidic activity in soil are able to remove the effects of soil sickness. The results obtained are discussed in connection with the hypothesis about the cause of soil sickness in apple.