The accumulation of soil-borne pathogens is the main driving factor of negative plant-soil feedbacks (NPSFs), which seriously restricts the sustainable development of agriculture. Using natural volatile organic compounds (VOCs) from plants or microorganisms as biofumigants is an emerging strategy to alleviate NPSFs in an environmentally-friendly way. Here, we identified α-terpineol from the VOCs of pine needles, confirmed the ability of α-terpineol fumigation in alleviating the NPSF of Panax notoginseng via significantly reducing seed decay rate, and also deciphered the underlying mechanism by which the soil microbial community is modified. α-Terpineol fumigation could suppress culturable fungi but enrich bacteria in a dose-dependent manner. Network analysis with high-throughput sequencing data revealed that α-terpineol could distinctly modify both fungal and bacterial communities. In detail, α-terpineol significantly suppressed the relative abundance of Ascomycota from 64.04 to 32.26%, but enriched the relative abundance of Proteobacteria, Acidobacteria and Actinobacteria. Subnetwork analysis further demonstrated that α-terpineol could directly or indirectly suppress fungal pathogens and enrich plant growth-promoting rhizobacteria (PGPRs). In vitro fumigation and co-culture experiments with culturable isolates validated these findings. The antagonism between beneficial bacteria and pathogens, and the synergistic growth promotion among α-terpineol-enriched bacteria might be involved in soil microbial community assembly. In summary, α-terpineol fumigation could directly or indirectly modify the soil microbial community to alleviate NPSFs, especially by suppressing fungal pathogens and enriching beneficial bacteria. This study suggests that VOCs from natural products are worth developing as biofumigants due to their multiple functions in modifying the soil microbial community.
It is important to study the law of water distribution in potted soil and the appropriate irrigation methods for improving the level of water-saving irrigation in greenhouse cultivation. In this study, pepper was taken as the experimental crop. Two kinds of drip irrigation models (root zone infiltrating irrigation and surface drip irrigation) and two kinds of irrigation emitter arrangements (a 3 × 120° distribution and a 2 × 180° distribution) were used to plot out the distribution pattern of soil water in a potted planting environment for two kinds of soils (Yunnan red loam and yellow-sand soil). Then, the growth indices of peppers were compared. The results showed that drip irrigation models and soil types had a significant interactive effect on soil water distribution (P < 0.01); in Yunnan red loam, the matric potential played a major role in the transport of irrigation water, while in yellow-sand soil, gravitational potential played a major role. Under root zone infiltrating irrigation, the high-water-content distribution area of the two types of soil is more continuous and balanced than that of surface drip irrigation, and the balance of water distribution of the yellow-sand soil is better than that of the red loam. In Yunnan red loam, the growth indices of peppers (plant height, stem diameter, fruit fresh weight, fruit dry weight, and similarly hereinafter) increased by 12.9%, 14.3%, 46.1%, and 36.8%, respectively; in yellow-sand soil, the growth indices under root zone infiltrating irrigation were 31.7%, 25.9%, 26.9%, and 35.3%, which were lower than those of surface drip irrigation. The experiment shows that in a greenhouse potting environment, Yunnan red loam with root zone infiltrating irrigation offers more water-saving potential. The results provide a theoretical basis and data support for the rational selection of drip irrigation models for facility agriculture in Yunnan.
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