Crnnr, R. V. nNo FBoer, G. 1977 . Effects

No abstract

A standard sand – cornmeal – nutrient salt medium, for use in the production of artificial inoculum of Helminthosporium sativum, is described. This inoculum induces uniform plant disease development when thoroughly incorporated with the planting soil. The results presented clearly demonstrate the necessity of using a series of infestation levels in studies of factors affecting disease development in artificially infested soil. It is shown that considerable reliance can be placed on treatment comparisons within an experiment but that comparisons between experiments are much less accurate. The role of a toxin (or toxins) in disease development in barley seedlings has been demonstrated. The toxic activity was found to be distinct from that frequently encountered on addition of organic matter to soil. Results obtained suggest that toxin adsorption by the soil may play an important role in reducing disease incidence and severity.

Soil treatments with nitrogen, lime and fumigation of mixed grain seeded in a 1:1 ratio of barley and oats were applied for 2 yr. They induced relatively few changes in agronomic characters even though a sloping terrain was employed the first year compared with a flat area the second year. Fumigation reduced spot blotch development the first year but not the second year. Kernel yield and protein content were relatively higher in mixtures when compared with average values for pure stands but they were not as high as the highest component.

No abstract