Abstract
Continuous cropping (CC) restricts the development of the medicinal plant cultivation industry because it alters soil properties and the soil microbial micro-ecological environment. It can also lead to reductions in the chemical contents of medicinal plants. In this study, we intercropped continuously cropped Pogostemon cablin (patchouli) with turmeric or ginger. High-throughput sequencing was used to study the soil bacteria and fungi. Community composition, diversity, colony structure, and colony differences were also analyzed. A redundancy analysis (RDA) was used to study the interactions between soil physical and chemical factors, and the bacteria and fungi. The correlations between the soil community and the soil physical and chemical properties were also investigated. The results showed that intercropping turmeric and ginger with patchouli can improve soil microbial abundance, diversity, and community structure by boosting the number of dominant bacteria, and by improving soil bacterial metabolism and the activities of soil enzymes. They also modify the soil physical and chemical properties through changes in enzyme activity, soil pH, and soil exchangeable Ca (Ca). In summary, turmeric and ginger affect the distribution of dominant bacteria, and increase the contents of the active ingredient in patchouli. The results from this study suggested that the problems associated with continuously cropping patchouli can be ameliorated by intercropping it with turmeric and ginger.
Highlights
Pogostemon cablin (Blanco) Benth is a well-known medicinal plant that is cultivated in the Philippines, Malaysia, and China (Swamy et al, 2010; Wu et al, 2010)
There were four experimental planting treatments, which were single patchouli group a where the patchouli had only been grown for the first time (SPa), single patchouli group b (SPb) where patchouli had been grown for a number of years, a continuously cropped patchouli intercropped with turmeric group (ITb), and a continuously cropped patchouli intercropped with ginger group (IGb)
The above results showed that intercropping can positively change the soil enzyme activities in the continuous cropping soil so that it becomes closer to the original state of the soil (SPa)
Summary
Pogostemon cablin (Blanco) Benth is a well-known medicinal plant that is cultivated in the Philippines, Malaysia, and China (Swamy et al, 2010; Wu et al, 2010). According to a recent study, the secretion of metabolites and leached substances from the plant increase under the CC system (Liu et al, 2020) This can promote the reproduction of pathogenic bacteria and increases the number and types of harmful microorganisms. It reduces the number and types of antagonistic, beneficial bacterial groups, breaks the soil microbial flora balance (Wu et al, 2015; Tan et al, 2016), and destroys the micro-environmental structure, which all lead to changes in soil microbial diversity. These changes alter soil ecological functions and limit the healthy growth and development of plants
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