Effect of vegetables-tomato rotation on soil microbial diversity, enzyme activity and physicochemical properties of vegetables in greenhouse

Abstract:

[Objective] Tomato is a vegetable that is largely affected by continuous cropping. We investigated the effect of the rotation of different crops and tomato on soil microbial diversity, enzyme activity, and soil physico-chemical properties, with the aim to select rotation crops suitable for tomato and thus to provide a theoretical basis for alleviating or avoiding continuous cropping obstacles in tomato cultivation.[Methods] Together with tomatoes, cultivated over 2 consecutive years, we planted six crops, namely Chinese cabbage (A), cucumber (B), pepper (C), eggplant (E), okra (F), and zucchini (G); treatments with continuous tomato cultivation (D) and temporary non-crop soil (H) were used as controls. Using 16S rRNA and fungal ITS region sequencing, soil enzyme activity, pH value, organic matter content, and available nitrogen, phosphorus, and potassium levels were determined. This enabled us to investigated the effects of the rotation of different vegetable crops and tomato on soil microbial diversity, enzyme activity, and soil physicochemical properties. [Results] The diversity index values of bacteria and fungi in soil from treatments A, B, C, E, F, and G were significantly higher than that in H. The community structure of bacterial phyla in D soil and in A, B, C, E, F, and G soils was relatively stable, albeit with differences in species abundance. Fungi were more sensitive to environmental changes than bacteria, and the differences in fungal community structures were greater than those in bacterial communities. The abundance of nitrifying bacteria (Nitrosomonas and Nitrosospira) in soil was significantly increased by rotation of eggplant and Chinese cabbage in the tomato field. Principal components analysis showed that the community structure of bacteria and fungi in E and H soil was significantly different from that of other treatments. Soil enzyme activity of different crops in rotation soils (A, B, C, E, F and G) was significantly different, but the change law was not obvious. Catalase activity in A, B, and H soil was significantly higher than that in other soils. According to the results of the soil fertility analysis, soil pH, organic matter, available nitrogen, and available phosphorus were the main contributing factors. [Conclusion] Crop cultivation can significantly increase the soil microbial diversity; rotation of eggplant and Chinese cabbage in the tomato field can significantly increase the abundance of nitrifying soil bacteria, which is beneficial to nitrogen metabolism and use. Rotation of cucumber and Chinese cabbage in the tomato field can significantly increase soil catalase activity, which is conducive to reducing the self-toxic effect produced by tomato in continuous cropping mode. Based on our results, eggplant, cucumber, and Chinese cabbage are potential dominant crops for avoiding or alleviating the tomato continuous cropping obstacle.

Key words:tomato;continuous cropping and rotation;soil microorganisms;enzyme activity