Microbes: a tiny but powerful tool
Posted 2nd November 2016 by Jane Williams
Crop yield gains over the last century largely resulted from advancements in biotechnology, coupled with extensive use of chemical fertilizers and pesticides. But what if we could increase crop yields while reducing our dependence on chemical fertilizers and pesticides?
Yield gains have slowed in recent years, and intensive application of chemical inputs has raised concerns about pollution and disease resistance. As chemical costs continue to rise and crop prices fall, today’s farmers are struggling to improve the sustainability of their operations and maintain profitability. New approaches to sustainably increase crop productivity are needed – and microbes are viewed as one tiny but powerful tool, with the potential to complement or replace traditional chemical fertilizers and pesticides.
Similar to our own microbiome, interactions between the plant, their environment, and a community of soil microorganisms – referred to as the phytobiome – is specific, complex, and interactive. Short crop rotations, specifically continuous corn and soybean production, negatively impact soil health and particularly the soil’s native microbial community. Thus, the ability to add microbes back to the soil is appealing. Success of a particular microbial product, however, will depend on a number of factors, such as plant species and cultivar, soil type and conditions, available moisture, and microclimate.
The microbes themselves, can be thought of as tiny chemical factories that excrete a variety of different molecules that trigger responses in plants to help withstand stresses and promote growth. Soil microbes form relationships with plant roots in the plant’s rhizosphere, providing various benefits such as drought tolerance, heat tolerance, enhanced nutrient uptake, and resistance to plant pests and diseases. For example, one well-studied group of beneficial bacteria are Pseudomonas spp. These bacteria can produce a variety of bioactive compounds and proteins shown to promote plant growth and protect against pathogens, including diacetylphloroglucinol (DAPG), auxin, and harpins.
Despite all of the known benefits, wide-spread adoption of microbial products has been limited to a large extent by inconsistent field performance. Many microbial products in the market today have been plagued by sub-optimal performance because they use microbes that are not well adapted to local conditions and/or experience high viability losses in the supply chain. Adaptability of the microbe to the local soil conditions and ability to establish populations around the plant’s root zone are key and will affect the microbes’ success in the field.
Historically, much of the R&D surrounding biologicals has been concentrated on discovery of plant-beneficial microbes through isolation and selection activities. Much less attention has been paid to development of appropriate formulation and delivery methods to assure viability of microbes at the point of application. Many current products are delivered as either liquid suspensions or in solid peat-based formulations and can experience significant population decline during their limited shelf life. In order to account for the death (oftentimes >99%) of viable microorganisms during storage and distribution, microbes are typically fermented in large centralized manufacturing facilities, then concentrated to increase populations in the product above the label limit. Thus, many microbial products currently on the market are largely ‘dead on arrival’ once they reach the farm.
The problem is many microbes by nature are not robust enough to survive the existing supply chain like chemical inputs. For example, most microbial products on the market contain spore-formers such as Bacillus spp. and Trichoderma spp. because of their ability to survive harsh conditions in a dormant form. Comparatively, less robust non-spore formers such as gram-negative Pseudomonas spp. and Azospirillum spp. have been repeatedly shown to have beneficial effects on multiple crops, yet successful commercialization has not occurred due to their incompatibility with the supply chain. In particular, elevated temperatures can lead to losses in viability quickly. Some typical strategies by industry to deal with viability losses and short shelf-life have involved concentrating product to account for microbe die-off, enhancements in formulation for stability, and/or refrigerated distribution and storage. All of these strategies are costly and undesirable.
3Bar Biologics developed a unique, simple-to-use delivery system that protects the microbes until the farmer activates the product when ready to plant. On-site growth of beneficial microbes short-cuts the conventional supply chain, resulting in the most viable microbes delivered to the field. This new approach for delivery opens the door to numerous beneficial microbes (particularly gram negative bacteria) proven in research, but never successfully commercialized to make it to the field. Furthermore, by moving the fermentation step to the point of use, the manufacturing footprint is minimized leading to less material waste and energy usage, and lower costs for production. The technology is currently undergoing field trials, but has consistently shown 4-5% yield increases across multiple sites in Ohio corn and soybean with zero incremental new chemical inputs.
Finally, microbial products fit well with Precision Ag strategies. Advanced technologies for variable rate seeding, nutrient application, and yield monitoring are allowing farmers to collect, analyze, and use data from their fields to precisely manage crop production. Targeted delivery of microbes either on-seed or in-furrow with pop-up fertilizer allows for precise application of the microbes with the seed using standard equipment. Additional data on a field’s soil health and microbiological makeup will further enable informed prescriptions to be made to better manage seeds, nutrients, biologics and other phytobiome components as part of the next-generation of Precision Ag.
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