Some properties of soils affecting russet scab and silver scurf of potatoes

Abstract

The relationship of soil ammonia, nitrates, pH, total bacteria,Streptomyces sp., temperature and moisture on the incidence of russet scab and silver scurf of potatoes was studied. The soil properties were changed by the addition of various levels of alfalfa, wheat straw and green rye residues. Within the limits of the changes caused by these residues, the most consistent relationship was found between the nitrate level in the soil and russet scab, and to a lesser extent, silver scurf. In both instances there was a general decrease in russet scab and silver scurf with increasing levels of nitrates. Also, in the only comparison made, an increasing total bacterial count in the soil resulted in a decreasing level of infection from silver scurf. In some instances the alfalfa, rye and straw residue applications caused small changes in soil pH, soil temperature, and soil moisture. These changes were not great enough to show any consistent significant relationship to russet scab or silver scurf, except for a significant negative correlation between soil moisture at the 6-inch level and silver scurf in both years.