Improved bacterial community diversity and cucumber yields in a rotation with kidney bean-celery-cucumber

Using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) methods, we investigated the effects of seven different crop rotation modes on cucumber rhizosphere soil bacterial communities. The bacterial diversity indexes in three growth periods showed that the diversity and evenness indexes of the kidney bean-celery-cucumber rotation were higher than those of the following rotations: tomato-kidney bean-cucumber, tomato-celery-cucumber, kidney bean-tomato-cucumber, cucumber-kidney bean-cucumber, cucumber-celery-cucumber, cucumber-tomato-cucumber, and cucumber-cucumber-cucumber. DGGE profiles of various rhizosphere soils showed six major bacterial populations: Proteobacteria, Sphingobacteria, Flavobacteria, Actinobacteria, Clostridia, and Acidobacteria. The yield of cucumber in the kidney bean-celery-cucumber rotation was higher than in other crop rotations (p < 0.05). Cucumber yield was strongly and positively correlated with soil microorganism diversity index (p < 0.01), and was also positively correlated with evenness index (p < 0.05). Our results suggest that the kidney bean-celery-cucumber rotation is suitable for cucumber cropping.