Articles
THE POTENTIAL USE OF AZIDES IN HORTICULTURE
Although they are highly toxic they show a broad action spectrum for many soil borne plant diseases.
In view of search for other broad working soil fumigants as e.g. methyl bromide a series of laboratory and small scale greenhouse experiments was carried out with indigenous soil for comparison with data from literature.
The paper gives a short review of known experimental applications and background of toxic activity.
Although both potassium and sodium azide were commonly used, the submitted experiments are all dealing with sodium azide as a source of the active hydrazoic acid.
The pH of the soil was artificially changed between 4.2 and the normal pH of 6.4 because of the great importance of pH in decomposition of the administered azide.
It was stated that under the studied conditions sodium azide has fungicidal or fungistatic properties, and moreover is less toxic for antagonistic fungi e.g. Trichoderma sp.. A lower pH, as already known, favours the liberation of hydrazoic acid.
Higher doses than mentioned in literature are not necessary although they were already much lower when compared to the doses of commonly used fumigants.
Experiments with tomato plants grown in infested soil showed better growth in the case of sodium azide treatments against Corynebacterium michiganense, Fusarium oxysporum f.sp. lycopersici and Pyrenochaeta lycopersici while also good effects of such treatments were stated in bean tests on Rhizoctonia solani infested soil.
Phytotoxicity was no specific problem compared to other fumigants and only diffusion through soil was rather poor but very easily became compensated by mixing the compound in the arable soil layer as effectuated for other powdered or granulated fumigant generators.
Positive and negative aspects are discussed with regard to application mode, toxicity, diffusion in soil of azides, pH influence, phytotoxicity, dose and effectivity.