Abstract
Regulatory pressure along with environmental and human health concerns drive the development of soil fumigation alternatives such as soil biosolarization (SBS). SBS involves tarping soil that is at field capacity with a transparent film following amendment with certain organic materials. Heating via the greenhouse effect results in an increase of the soil temperature. The organic amendments can promote microbial activity that can enhance pest inactivation by depleting oxygen, producing biopesticidal fermentation products, and competing with pests. The properties of the organic amendments can heavily influence the type and magnitude of these effects. This study evaluated the viability of chitin as a novel SBS soil amendment to influence soil fungal and bacterial microbial communities, including control of the plant pathogen Fusarium oxysporum f.sp. lactucae (FOL). Changes to FOL and the broader soil microbiota were monitored in response to biosolarization using 0.1% (by dry weight) amendment with chitin (Rootguard). FOL suppression was only observed in chitin amended soils that were incubated at room temperature, not under solarized conditions. Conversely, it decreased solarization efficacy in the upper (0–10 cm) soil layer. The presence of chitin also showed increase in FOL under anaerobic and fluctuating temperature regime conditions. Biosolarization with chitin amendment did exhibit an impact on the overall soil microbial community. The fungal genus Mortierella and the bacterial family Chitinophagaceae were consistently enriched in biosolarized soils with chitin amendment. This study showed low potential FOL suppression due chitin amendment at the studied levels. However, chitin amendment showed a higher impact on the fungal community than the bacterial community. The impact of these microbial changes on crop protection and yields need to be studied in the long-term.
Highlights
Soil-borne pathogens and pests are a major and complex issue inhibiting agricultural production [1, 2]
Lettuce can be severely damaged by Fusarium wilt, a disease caused by the pathogenic fungus, Fusarium oxysporum f. sp. lactucae (FOL) [6]
One study found that a 0.5% Fusarium disease severity corresponded to a revenue loss of $11.66 per acre, while a 2.2% Fusarium disease severity corresponded to a revenue loss of $100.85 per acre [11]
Summary
Soil-borne pathogens and pests are a major and complex issue inhibiting agricultural production [1, 2]. Pre-plant chemical fumigation is the most effective way to control soil-borne pathogens, owing to cost and regulatory constraints, this practice is no longer an option for production of most crops [3, 4]. For this reason, it is critical that effective and environmentally sustainable alternatives to chemical fumigation are developed. Lettuce can be severely damaged by Fusarium wilt, a disease caused by the pathogenic fungus, Fusarium oxysporum f. Management of Fusarium wilt is a priority for lettuce growers where this disease occurs
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