Response of Soil Microbial Community Diversity to Long-Term Cultivation of Rice ( Oryza sativa L.)/Cherry Tomato ( Lycopersicon esculentum Mill.) in Rotation

The crop rotation periodicity has always been a concern of agricultural researchers. This study was the first investigation on the effects of long-term continuous cultivation with rice/cherry tomato rotation on soil microbial community diversity. The main objective was to analyze the optimal rotation years of rice/cherry tomato from a micro-ecology perspective so as to provide theoretical basis for effectively avoiding continuous cropping obstacles of cherry tomato. Soil samples were collected from the surface layers with rice/cherry tomato rotations for 1 year (1a), 3 years (3a), 5 years (5a), 7 years (7a) and 10 years (10a). The microbial community diversity was determined via high-throughput sequencing. The results showed that alpha diversity of soil microbial communities was the highest at 5a and then gradually decreased during 5a to 10a. Beta diversity results revealed that microbial community structure was significantly different among 1a, 3a to 7a and 10a, but there were no clear differences among 3a, 5a and 7a. The abundances of soil beneficial bacteria Gemmatimonadetes, Bacteroidetes, Chloroflexi, Nitrospirae and beneficial fungi Mortierella , Trichoderma, Penicillium were the highest at 5a or 7a. Those of soil pathogenic fungi Fusarium and Aspergillus were the lowest at 5a and 7a, respectively. However, the relative abundances of the above-mentioned beneficial microorganisms began to decline, while those of pathogenic fungi began to increase after 5a or 7a. Soil available phosphorus, available iron and available zinc were common important factors affecting the community structure of bacteria and fungi, as indicated by significant positive correlations between the environmental factors and microbial communities. In conclusion, the soil microbial diversity began to decline and the micro-ecological balance was broken after continuously planting 5a to 7a with rice/cherry tomato rotation, which would lead to new continuous cropping obstacles.