Correlation analysis of main environmental factors and phenolic acids in continuous tobacco cropping soils using Mantel Test

Flue-cured tobacco is a crop sensitive to continuous cropping. Continuous cropping over the long-term has seriously affected growth and production quality of flue-cured tobacco by affecting the soil environment. Phenolic acids can cause growth disorders under continuous cropping. Although the interaction between phenolic acids and other environmental factors after entering the soil environment has not much been investigated, it is clear that phenolic acids occur in soils under continuous tobacco cropping. The action process and the role in limiting continuous cropping are critical for successful tobacco cultivation. An experiment was conducted to determine the relationship between phenolic acids and soil environmental factors in the soil by analyzing the correlation between various environmental factors and phenolic acids in soil. The purpose was to identify the environmental factors affecting the concentration of phenolic acids in soils under continuous cropping systems. Soils of four tobacco fields with different durations of continuous cropping (4 a, 6 a, 8 a, 14 a and 16 a) were sampled. The changes in phenolic acids, physical and chemical properties, enzyme activities and bacterial diversities in soils under different continuous cropping years of tobacco were investigaed. The correlation between phenolic acids and soil environmental factors was analyzed using the Mantel Test. The results showed that long-term continuous cropping of tobacco resulted in an increase in soil phenolic acids content. Higher pH of soil under tobacco continuous cropping resulted in low soil organic matter content, but increased available potassium. The activities of catalase, urease acid phosphatase, and invertase first increased and then later decreased. When continuous cropping for less than 6 years, bacterial community structure changed little. However, bacterial community structure changed significantly after 8 years of continuous cropping. In general, continuous cropping changed bacterial community structure and reduced community diversity. Mantel Test analysis showed that phenolic acid content was significantly correlated with enzymes activities and physical and chemical properties of soil. Bacterial abundance had the highest correlation with soil physical and chemical properties. There were differences in correlation between different phenolic acids and soil environmental factors. P-hydroxybenzoic acid and phoronic acid had the highest correlation with physical and chemical properties of soil, enzyme activity and bacterial abundance in soils. Therefore, phenolic acids in soils under continuous tobacco cropping obviously accumulated over time with deteriorated soil environment. The accumulation of phenolic acids was affected by soil physical, chemical and biological properties of soil. P-hydroxybenzoic acid and tartaric acid were two kind phenolic acids most affected.