Volume 41, Number 8 | MARCH 17, 2015
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PRACTICAL PRODUCTION TIPS FOR THE PRAIRIE FARMER
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INOCULANT: Finding the right formulation Liquid, peat or granular? Choose the best one for your fields By Melanie Epp
I
noculants can offer tremendous value to growers at a reasonable price. Under ideal conditions, all three formulations — liquid, peat or granular — can be equally effective. As conditions deteriorate, though, differences can occur. The different types of inoculants refer to the substrate that the rhizobium bacteria are applied to, says Dr. Diane Knight, soil science professor at the University of Saskatchewan. Liquid inoculants are broth cultures that are sold either refrigerated or as frozen concentrates. Usually, they are mixed with water and sprayed into the seed furrow at planting. “Liquid inoculants are probably the least popular because they need to be refrigerated during shipping and storage,” says Knight. “In Western Canada, liquids are not as common as peat and granular inoculants.” With peat inoculants the bacteria adhere to a commercial grade, finely ground peat moss. “The peat provides a relatively inert substrate that the bacteria can survive on in high numbers,” says Knight. “Peat inocu-
lants sometimes are manufactured with a ‘sticker’ substance added to adhere the peat inoculant to the seed. With non-sticking formulations the farmer can add a sticker separately. The powdered peat is applied directly to the seed at seeding so that the bacteria are in direct contact with the seed.” Granular inoculants are small pellets, usually made of an inert clay — although other substances have been used — that the bacteria are applied to. Similar to peat, granular inoculants provide an inert stable substrate that supports the bacteria in high numbers. Granular inoculants are applied to the soil rather than to the seed.
Choosing the right rhizobium Crops are very selective about the type of bacteria they use to form nodules that result in the desired nitrogen fixation. Field peas, lentils and faba beans, for instance, require Rhizobium leguminosarum species. Chickpeas require Mesorhizobium cicero, dry beans require Rhizobium phaseeoli and soybeans require Bradyrhizobium japonicum.
photo: thinkstock
The most important factor is to choose the right inoculant for the pulse crop you’re growing. Choosing the wrong one, says Diane Knight, “is the same as applying nothing, just more expensive.” Chickpeas require the bacteria Mesorhizobium cicero. “Apply a pea inoculant to soybean and no infection of bacteria will occur,” says Garry Hnatowich, research director at the Irrigation Crop Diversification Corporation at Outlook, Sask. Knight agrees. “Purchasing the correct inoculant for a particular pulse crop is the most important decision — makes far more difference than whether it is a peat/granular or liquid inoculant,” she says. “Applying an inoculant for soybean onto pea will have no benefit. It is the same as applying nothing, just more expensive.”
Which inoculant works best? Powdered peat-based inoculants were first introduced for sale in North America in 1897, says Hnatowich. “Up until about 25 years ago, they remained the only commercial formulation available to growers,” he says. “This formulation was awkward to apply
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with accuracy, dusty and had poor adhesion with the seed they were applied to,” says Hnatowich. “Many farmers resorted to mixing in ‘glues’ to help the inoculant stay on the seed, such as powdered milk, honey and even cola.” “Liquid inoculants alleviated much of the application difficulties,” he says. “They could be conveniently metered and applied as seed was augered into the truck or into the seeder.” As the number of seed/input tanks on seeders increased, more granular inoculants were developed. Now application rates can be easily calibrated, and they offer a positional placement within the seed-row that can be beneficial, says Hnatowich. “The three types differ in the way the bacteria are delivered to the system,” says Knight. “Because they are delivered differently, the
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Wheat & Chaff .................. 2 Features . ........................... 5 Crop Advisor’s Casebook . 6 Columns ............................ 15 Farm Safety . ..................... 24 Machinery & Shop............. 28
Winter wheat, winter kill lisa guenther
page 5
Pick up truck special
scott garvey page 28
Cattleman’s Corner .......... 37 FarmLife ............................ 44
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