Legumes are the foundation of prairie organic agriculture and high quality rhizobium inoculants are important to maximize their nitrogen fixation. Without proper inoculation, legume yields are at risk.
A recent decision regarding seed inoculants at the Organic Crop Improvement Association International annual meeting in Lincoln, Nebraska, has made choosing seed inoculants much easier this spring.
The OCI reversed its decision last year to ban the use of legume inoculants that have been irradiated as a form of sterilization for their peat carriers. The ban was originally intended to cover irradiation in food processing and not areas such as the sterilization of peat carriers for the production of legume inoculants.
The sterilization of peat and clay carriers for inoculant production was recommended by several scientists who conducted extensive research on the quality of legume inoculants in North America.
Their studies indicated that some low quality non-sterile peat-based inoculants contained high levels of organisms that can compete with the rhizobium.
In some cases, contaminant organisms outnumbered beneficial rhizobium and were shown to inhibit the rhizobium and effective nodulation.
Researchers also found that some of the contaminant organisms could cause plant, animal and human diseases.
Irradiation of carriers for seed inoculants does not affect the inoculant organisms, nor does it have known risks for soils or crops.
Irradiation does not make the peat radioactive, nor does it alter the physical structure of peat. It is a more effective source of sterilization than chemicals or heat. The spores of some fungi require high temperatures in steam and heat sterilization that are impractical to use in the commercial production of legume inoculants.
Last year’s ban on irradiation included the product Jump Start from Philom Bios, which contains a soil fungus called penicillium bilaii. Jump Start is also included in a legume inoculant under the name Tag Team.
Penicillium bilaii is a naturally occurring soil microorganism that is used as a seed inoculant to make phosphorus more available. Most Saskatchewan soils have an abundance of phosphorus, but it is mostly in unavailable forms.
Rock phosphate is commonly used on organic farms, but again, most of it isn’t immediately available for use by plants. It is recommended to use Jump Start in combination with rock phosphate.
Low phosphorus availability is a commonly reported problem on prairie organic farms that is not easily corrected with just rotation, or the addition of rock phosphate or animal manure. Because prairie organic farms cover relatively large acreages, they are not able to have enough livestock to provide sufficient phosphorus fertilization with just animal manure.
A continued prohibition on the use of irradiated inoculants would have caused problems on organic farms. While legume inoculants that do not use irradiation for sterilization are available, shortages of inoculants this year could have left some farmers without any legume inoculants. Many farmers were also confused and worried about which inoculants were acceptable. This left organic farmers uncertain about legume production and may have discouraged some from growing legumes.
In the case of Jump Start, there was no alternative. A loss of this product would have been a serious blow to organic farming on the Prairies.
While innoculant selection is now much easier, there are still things to watch for.
Make sure you contact your certification agency for a list of approved inoculants.