Intercropping With Turmeric or Ginger Reduce the Continuous Cropping Obstacles That Affect Pogostemon cablin (Patchouli)

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.

Keywords: Pogostemon cablin (patchouli); continuous cropping obstacles; high-throughput sequencing; intercrop; microorganism diversity.

FIGURE 1

Radar distributions of soil physical factors. The three diagrams have been divided according to the measured values of the soil physical properties. SPa, cropping with patchouli for 1 year; SPb, continuous cropping with patchouli over a number of years; ITb, continuous cropping with patchouli and intercropping with turmeric; and IGb, continuous cropping with patchouli and intercropping with ginger. P, available potassium; AK, available potassium; Ca, exchangeable Ca; EC, electrical conductivity; Cu, available Cu; Zn, available zinc; EB, effective boron; OM, organic matter; AN, alkali-hydrolyzable nitrogen; EMg, effective magnesium; EI, effective iron; EMo, effective manganese.

FIGURE 2

Soil enzyme activities when the various planting modes were applied. ****P < 0.0001, ***0.0001 < P < 0.005, and ns, no significant difference.

FIGURE 3

Soil microbial NMDS models for bacteria and fungi when the various planting modes were applied. (A) The differences in the bacterial community structures. (B) The differences in the fungal community structures.

FIGURE 4

Clustering results and the relative abundance heat maps for the bacteria (A) and fungi (B).

FIGURE 5

Evolutionary diagrams for the bacteria and fungi when the various planting modes were applied. Each small circle in the figure represents a category at the group level. The inner to outer circles are different categories. In the horizontal classification tree, the diameter of the circle is proportional to the relative abundance. The groups are distinguished by different colors where the colored nodes represent microbial groups that play an important role in the corresponding color group. The yellow nodes represent microbial groups that did not play an important role in any of the treatment groups. (A) Differences in classification levels of bacterial community from phylum to species. (B) Differences in classification levels of fungal community from phylum to species.

FIGURE 6

Comparison of the bacterial functions in the soil after continuous cropping with patchouli (A), after continuous patchouli cropping and intercropping with turmeric (B), and after continuous patchouli cropping and intercropping with ginger (C).

FIGURE 7

Correlation analysis between the rhizosphere bacteria and fungi, and the soil physical and chemical properties when the soil was used to grow patchouli. (A) Redundancy analysis (RDA) between the soil and the bacterial community. (B) RDA between the soil and the fungal community.

FIGURE 8

Correlation diagram showing the relationships between the dominant bacteria and fungi and the soil physical and chemical index network. P, available potassium; Ca, exchangeable Ca; Cu, available Cu; OM, organic matter; and AN, alkali-hydrolyzable nitrogen. (A) Correlation network of the dominant bacteria and the soil physical and chemical index. (B) Correlation network of the dominant fungi and the soil physical and chemical index.

FIGURE 9

Baiqiuli content in the patchouli when the various planting modes were applied.