How To Care For Inoculation Products
December 29, 2014 In recent years, inoculant manufacturers have focused their research and development efforts on finding ways to improve inoculants, according to The Ohio State University Research and Extension. One focus is improving strain selection and increasing the number of viable bacteria per gram of product. Combining strains of Bradyrhizobium japonicum that are most productive in different environments results in products that are productive over a wider range of environments.
Other areas of focus have been on easing application through the development of liquids and improved dry products. Combining organisms that offer plant growth promotion hormones or disease control in conjunction with regular rhizobials is another new development. Other areas of interest are the biological signals that induce nodulation. Combining the signal compounds with inoculants also allows companies to speed up the inoculation process. The addition of “extenders” to inoculation materials allows the materials to be applied to seed up to thirty days or more before planting without loss of productivity if the seed is stored properly.
The extender materials also extend the longevity of bacteria cells applied to seed that has been treated with fungicides and in some cases allows the combined application of fungicides and inoculation materials. High quality inoculants contain over 2 billion live bacteria per gram, and use at the recommended rate results in 800,000 to 1,400,000 bacterial cells per seed depending on seed size and quality of the inoculant material.
But perhaps the best way to improve inoculants is to care for them properly. According to OSU Extension, rhizobia cells survive best at temperatures of 40 – 80 degrees F. Prior to application, inoculants should be stored in a cool place and out of direct sunlight. Packets exposed to sunlight during the planting season will overheat rapidly due to the greenhouse effect and all the bacteria can be killed in less than an hour of exposure.
In addition, when transporting the inoculant to the field, try to keep it cool. The back of the cab and out of the sunlight is best, and under a parked truck in the cool shade when in the field. Sunlight is a problem of heat, not radiation, so keeping the inoculation material in its box will stop some heat absorption. Under normal conditions the shelf life of inoculation materials varies from a few months to two years depending on the formulation and additives in the product. Dry materials generally have shorter shelf lives than liquids, but some sterile products have a shelf life approaching that of liquids.
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