Abstract
The adoption of anaerobic soil disinfestation (ASD), a biologically-based method for the management of soilborne pests and pathogens at the commercial scale strictly depends on the availability of effective and low-cost sources of carbon (C). A three-phase pot study was conducted to evaluate the performance of twelve cover crop species as alternative sources of C in comparison to molasses. Buckwheat produced the greatest above-ground and total plant dry biomass and accumulated the largest amount of total C. In the second phase, simulating the application of ASD in a pot-in-pot system, molasses-amended soil achieved substantially higher levels of anaerobicity, and lowered soil pH at 3 and 7 days after treatment application compared to soil amended with the cover crops tested. In the third phase of the study, after the ASD simulation, lettuce was planted to assess the impact of cover crops and molasses-based ASD on lettuce yield and quality. The treatments had limited effects on lettuce plant growth and quality as none of the treatments caused plant stunting or phytotoxicity. Tested cover crop species and molasses had a significant impact on the availability of macro and micro-elements in the soil, which in turn influenced the uptake of minerals in lettuce. Fast growing cover crops like buckwheat or oat, capable of accumulating high levels of C in a relatively short time, may represent a viable alternative to substitute or be combined with standard C sources like molasses, which could provide an on-farm C source and reduce cost of application. Further research is needed to assess the performance of cover crops at the field scale and verify their decomposability and efficacy in managing soil-borne pests and pathogens.
Highlights
The sustainable management of soil borne pests and pathogens is a significant challenge for specialty crop growers who need new integrated strategies to preserve soil health for the long term [1,2].In the past, conventional growers have addressed these issues primarily by relying on the use of chemical soil fumigants, especially the use of methyl bromide [3], overlooking some of the long-term negative effects on soil health and the environment
Keeping the soil under reducing conditions for a few days or weeks, the anaerobic decomposition of the C source by facultative and obligate anaerobic microbes leads to the production of organic acids, volatile organic compounds (VOCs), and the development of micro environmental conditions that are suppressive for soilborne pests and pathogens [8,11,12,13,14,15,16,17]
Comparing the performances of twelve cover crops in a preliminary pot experiment conducted in the greenhouse under controlled conditions, a significant amount of variability was observed between different cover crop species in terms of fresh and dry biomass production as well as in terms of total C
Summary
The sustainable management of soil borne pests and pathogens is a significant challenge for specialty crop growers who need new integrated strategies to preserve soil health for the long term [1,2].In the past, conventional growers have addressed these issues primarily by relying on the use of chemical soil fumigants, especially the use of methyl bromide [3], overlooking some of the long-term negative effects on soil health and the environment. Methyl bromide was commonly used as a soil fumigant due to its high efficacy against a wide spectrum of soilborne pests and pathogens, and for being relatively inexpensive and easy to use across a range of cropping systems. Few substitute chemical fumigants have been registered and to accommodate the increasing demand by consumers for more sustainable food production systems, the horticulture industry is seeking non-synthetic, less disruptive, and possibly integrated, alternative solutions for the management of soilborne pests and pathogens. Among the non-chemical alternatives, anaerobic soil disinfestation (ASD), is emerging as one of the most promising solutions to generate disease suppressive soils [2], being a biological method that is effective in managing a wide range of pathogens and pests in different cropping systems and under different environmental conditions [6,7,8]. Being a microbiologically based method, ASD efficacy is enhanced by higher temperatures, and research is needed to assess its efficacy in temperate regions such as the U.S Mid-Atlantic region characterized by relatively low temperatures during the period when ASD would be applied
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