Responses of soil microbial community structure, potential ecological functions, and soil physicochemical properties to different cultivation patterns in cucumber

Changing crop cultivation patterns may alleviate the negative effects of continuous cropping by altering soil characteristics. But how soil properties and microbial states are specifically altered is largely unknown. In this study, soil properties and cucumber growth were investigated after nine years under six cultivation patterns. The results showed that the different cultivation patterns significantly altered the bacterial and fungal communities of the bulk soil, and bacteria appeared to be more sensitive to cultivation pattern than fungal communities. In pairwise comparisons of the six cultivation patterns at the phylum level, all 15 comparisons showed significant differences in bacterial phyla, and 6 showed significant differences in fungal phyla. The paddy upland rotation pattern (pattern 1) had the greatest effect on the types of soil microorganisms, with 5 unique OTUs for bacteria and 17 for fungi. The results of unweighted pair-group method with arithmetic mean (UPGMA) analysis between bulk soil and rhizosphere soil suggested that differences in bulk soil microbes led to differences in rhizosphere soil microbes. Bacterial and fungal genera (Serratia, Arachidicoccus, Penicillium, etc.) in the rhizosphere soil were significantly associated with cucumber agronomic traits. Compared with the other cultivation patterns, pattern 1 and the garlic rotation pattern (pattern 6) promoted the succession of soil microorganisms in a direction beneficial to plant growth through enrichment of more microbiota antagonistic to plant pathogens. Different cultivation patterns also changed the abundance of potential microbial functional genes. Pattern 1 had an increased abundance of microorganisms associated with functions such as N and P cycling, arsenic detoxification, and aromatic compound degradation. Pattern 1 also significantly weakened the trend of soil acidification and produced a significantly higher soil pH than the other five patterns. Therefore, paddy upland rotation and garlic rotation cultivation patterns may be considered as alternatives for sustainable cucumber production in the study area.