Nitrogen fixing inoculants have been in widespread use for decades, but is there a future for inoculants that will extract other nutrients from the soil?
Inoculants are one of three fertility trends on the horizon, says Mosaic chief agronomist Dan Froehlich in Minneapolis.
“First, we’re going to see more fertilizer banded at seeding time. This allows a cutback in rates,” Froehlich said.
“You Canadians are already way ahead of American farmers in that.”
Farmers will gain access to more efficient fertilizer products that aren’t tied up in the soil.
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Froehlich said inoculants will be part of this development because they will be needed to help release the nutrients and make the fertilizer more efficient.
“Third, phosphorus, which is typically tied up in the soil, will be the next big frontier for inoculants,” Froehlich said.
“The challenge will be timing. Researchers need to get the phosphorus to release when the plant needs it. Most fungi and bacteria are temperature sensitive, but we keep moving our planting dates earlier in the spring when the soils are still cold. That creates a timing problem.”
Froehlich said it’s smart to apply some phosphorus and nitrogen fertilizer with the seed because fungi and bacteria don’t become active until soil temperatures climb.
“This gives the plant enough early growth so the roots are already starting to develop when the inoculants become active,” he said.
“They’ll have a bigger, healthier root structure to attach themselves to. From the work I do in Canada, I think most farmers there are already putting enough fertilizer close to the seed to get that early growth.”
Froehlich said too much of a good thing can be a bad thing.
“Keep in mind that you should follow the recommendations. If you apply too many bacteria, each one doesn’t have to work as hard. They get lazy and your crop will suffer.”
Laila Yesmin, director of research and development at Brett Young Seeds in Winnipeg, doesn’t think inoculants can replace fertilizer.
“We need the bacteria products to be integrated with the fertilizer to help make the fertilizer more efficient,” she said.
We want the bacteria to absorb nutrients from the fertilizer and then release them slowly, but later in the growing season when they (bacteria) die off.”
Yesmin said microbial fungi and bacteria concentrate near the root system, feeding off the excrement and waste tissue of the root.
This symbiotic relationship benefits the plant and the microbe by moving toxic waste away from the plant roots and helping the plant process the microbes.
Most of the microbial population dies when the growing season ends because they depend on the living plant.
However, a few robust inoculant bugs can occasionally survive the death of their host plant and remain alive in the soil, joining the indigenous microbial population that has always lived at that specific site.
These indigenous microbes are of far less use to commercially grown crops so new inoculants will need to be applied before next year’s crop is grown.
However, Yesmin said it is possible to produce enough tough survivors from the applied inoculant population to make a difference to commercially grown crops.
“In many American soybean fields, yield comparisons now show very little difference between inoculated and non-inoculated strips,” she said.
“After many years of applying soybean- specific inoculants, there are now enough long-term surviving microbes that farmers can stop applying inoculants.”
Yesmin said researchers agree they will soon move beyond microbes for nitrogen and phosphorus.
“The prairie soils have an enormous amount of potassium locked in the soil and lots of micronutrients. We will work on developing inoculants to release those nutrients, but with fungi and bacteria, it’s very difficult to release the negatively charged elements like inorganic phosphate.”
Biochar might be the next big step in soil enhancement technology, said Jeff Schoenau at the University of Saskatchewan.
“Biochar is a byproduct of pyrolysis, or low-oxygen combustion. It’s a type of charcoal and a good source of carbon when it’s in the soil.”
It can be baked from manure, woody material or waste from crop and food processing.
Schoenau said biochar reduces leeching and gaseous loss of soil nutrients.
He has just begun work on biochar technology and doesn’t expect definite results for a couple years.
However, he said inoculants for nitrogen fixation have come a long way in a short time. As a result, producers have better nitrogen levels and yields in their legumes and improved nitrogen for subsequent crops.
“We’ve also seen the development of phosphorus soluble fungi inoculants that have given farmers another option for improving phosphorus fertility in their crops,” he said.
“Down the road, I think we’ll see other types of microbial inoculants. For example, aarbuscular mycorrhizal fungi can colonize the roots of most crops grown in Canada.
“The AM fungi extends the roots so they can better access phosphorus and water. Some people have suggested it can help the roots access nitrogen. We’ll see.”
Schoenau also thinks researchers will commercialize fungi that can scavenge micronutrients from the soil.
Micronutrients are not mobile in the soil, so a fungi that can extend the root system can help the plant access more of those micronutrients in the root rhizoshpere. He said these microbial agents are similar to the products already under development at Brett Young.
Schoenau said other organic soil amendments have a proven benefit but are not classified as inoculants. These include manure and byproducts from food processing and bioenergy facilities. He said bin stillage and wet distillers grain are two good soil amendments.
“But regardless of what you put in your soil, you can’t get something for nothing. If you use soil to grow plants, nutrients are consumed. They have to be accounted for somehow.”
What does Schoenau have to say about bacteria, fungi and new types of inoculants in distant future? Does he see hope for that proverbial magic bullet to replace commercial nitrogen fertilizer?
“Well, the holy grail of some researchers continues to be an inoculant that will completely replace commercial nitrogen.
“This microorganism would fix nitrogen from the atmosphere for all crops, including cereals and oilseeds, in what we call an asymbiotic fashion. That’s different from the mutually beneficial relationship our present inoculants have with legumes.
“People have worked on that for quite a number of years now, but so far there’s no progress. It may be possible someday. Maybe.”
