Beziehungen zwischen Fruchtwechselfolgen einerseits und dem Auftreten der Tomaten-Umfallkrankheit und der Zwiebelwelke sowie den Populationen ihrer Pathogene und des Antagonisten Bacillus subtilis im Boden andererseits

Crop rotation showed a pronounced effect on incidence of tomato damping-off and onion (Fusarium) basal rot as well as on the soil population of the two disease incitants. Out of nine rotation systems, wheat/sorghum and wheat/maize preceding tomato diminished damping-off while clover/maize, lentil/sorghum, wheat/sorghum and wheat/maize preceding tomato diminished damping-off while clover/maize, lentil/sorghum, wheat/sorghum and wheat/maize preceding onions increased basal rot incidence. First crops of the rotation system as well as the second crop were of noticeable effect onRhizoctonia solani andFusarium oxysporum f. sp.cepae as onBacillus subtilis (antagonistic to both fungi) population in soil. Almost all rotations increased population ofF. oxysporum f. sp.cepae andB. subtilis in soil while response ofR. solani was variable. The results show thatBac. subtilis did not correlate with tomato damping-off or onion basal rot. There must be some other factors found in the soil that play a role in effect of crop rotation on disease incidence.