The effects of induced soil aggregation on the occurrence ofAzotobacter andStreptomyces

Summary

• 1. The effect of soil aggregation produced by synthetic soil conditioners on the occurrence ofAzotobacter andStreptomyces in a highly fertile Belgian loess soil was investigated by various methods.

• 2. Wide differences in levels of soil aggregation introduced technical problems which made impossible the obtaining of strictly comparable results.

• 3. In general increased soil aggregation tended to favour an augmentation ofAzotobacter andStreptomyces in the soil used and under the environmental conditions prevailing.

• 4. However, it seemed clear that in such investigations straight-line relationships cannot be obtained reliably because other soil micro-organisms also are favoured by such treatments and competitive effects may be emphazised from time to time.

• 5. No evidence was found of any inherent toxicity in the soil aggregating products used when they were employed within commercially practical limits.