Fertilizer, so far, the key to yield; inoculation and fixation not as important as for other prairie pulse crops
Inoculating solid-seeded CDC Blackstrap beans across five research areas in Saskatchewan produced no tangible results.
“What we found is that we had a complete inoculant failure. The product that we were able to access did not offer us any yield advantage to inoculation,” said Garry Hnatowich, research director at the Irrigation Crop Diversification Corp. in Outlook, Sask.
Agri-ARM is a network of producer-directed applied research and demonstration organizations in Saskatchewan.
Hnatowich said Canadian manufacturers indicated they would no longer produce dry bean inoculant for Canada, however an American made inoculant was donated for the study, but remains commercially confidential.
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“Inoculants are notoriously ineffective on dry beans anyway,” he said.
Hnatowich spoke about dry bean production under solid-seeded conditions (instead of the more commonly used wide row spacings) and whether to inoculate or fertilize.
In 2019, five Agri-ARM research sites were used to grow the variety, which research is showing has great promise as a dryland, high-yielding bean with high pods.
“You get one of those three things but not usually all of them in one variety,” said Lana Shaw, research manager at South East Research Farm in Redvers, Sask., one of the research areas.
The four dryland locations were at Scott, Yorkton, Indian Head and Redvers. As a comparison, one irrigated site was grown at Outlook.
Hnatowich led the one-year study from ICDC in Outlook.
Three of the test plots were in black soil zones and two were dark brown. One of the brown zones was irrigated at Outlook.
Most black beans are grown in Manitoba and Alberta, but CDC Blackstrap could become a good choice for solid-seeded production in Saskatchewan.
In Saskatchewan, beans are historically seeded at 22-inch row spacing, but this variety may allow for narrower row spacing of 10- or 12-inch rows, which Hnatowich said enables the producer to use conventional farm equipment as well as direct harvest the crop.
“The reason we chose Blackstrap is it’s really the only variety out there right now that has the pods forming on the plants high enough up that they can lend themselves to direct combining or swathing,” he said.
During the test trials the various inoculant treatments were applied with or without nitrogen fertilizer additions. The nitrogen fertilizer additions included soil plus fertilizer to equal 80 pounds, which Hnatowich described as an old-school formula.
“There’s a rule of thumb that a fertilizer plus soil equals 80 pounds,” he said.
“This might not be surprising. Typically, we know with the rhizobium inoculants that anything exceeding 50 pounds of nitrogen fertilizer in the system will often inhibit nitrogen fixation. And if we get too much higher than 50, 60, 70, 80 lb., we’ll often totally knock off nitrogen fixation in the plant.”
Added Shaw: “The rhizobia bacteria forms nodules in the roots of legumes. If you give the plants a lot of nitrogen fertilizer, they won’t bother forming those associations with the bacteria to fix atmospheric nitrogen. They will just use the fertilizer instead, which is generally what we’re not trying to achieve.”
Hnatowich said the irrigated Outlook area tends to have the highest yields and a long-term history of bean production, which is why he focused his findings more on the four dryland sites that were solid seeded.
“We’re not going to increase acreage in irrigated areas of the province. The intent is to move it off on to the dryland. On those dryland sites, they responded proportionally higher than the Outlook site did.”
“We ended up with close to 600 lb. or better than 600-lb. yield gain to the fertilizer nitrogen application at the dryland sites,” he said.
In Outlook, he said he was pushing 3,000 lb. per acre of beans with the fertilized trials, but for all dryland sites the yield was 1,800 to 1,900 lb.
Even the Outlook land that had grown beans in the past, Hnatowich did his own careful analyses to look for the infection by the potential rhizobium.
“I went into each and every plot and dug up roots. We had a treatment where there was no inoculant applied. I went in and I could find nodules, which meant that the bacteria that will cause nitrogen fixation to occur was there. It was in the soils. So, what I was doing was looking for those things and finding them. Then I went in where we did apply this strain of inoculant and I was not finding any more than where we didn’t apply any inoculant. So, it was telling me that soil bacteria was doing the job,” he said.
“What it was doing was riding on indigenous background populations that historically have been built up at Outlook and they contributed to 2,000 lb. plus of yield for me.”
While the yield dropped on the four dryland sites to less than 2,000 lb., they all had a significant yield response to the nitrogen fertilizers.
However, most of the test plots across the four dryland locations experienced significant drought-like conditions during the study, which affected yields to different degrees, depending on moisture levels.
Indian Head had the greatest decline in yield due to dryness on heavily textured soils.
“Establishment can often be difficult with beans under heavy textured soils. They tend to like a loam type of texture. That being said, if you can get them out of the ground, they don’t mind the heavy clays. The moisture-holding capacity of the place can certainly be a benefit. But where no nitrogen into the system, no yield. You put 80 lb. into it and you push into about 800-900 lb. worth of beans coming out,” he said.
While there was a consistent lack of response to inoculation, there was a highly significant yield response to nitrogen fertilization on the four dryland sites.
The surprise here for the researchers were that the results were consistent everywhere, which raised the question of why.
“Why did we fail to see an inoculant response with this pulse crop,” he said.
“The bottom line is two possible things could have happened. The bacteria did not recognize the variety of bean that we were growing and then failed to inoculate properly. The second thing is the strain may not be adapted to western Canadian soil conditions,” he said.
A common perception, he said, is that inoculants put on the seed or into the ground (as a granular formulation) provides adequate nitrogen fixation.
Not necessarily so, he said.
“The perception is for most pulse crops that there will be an economic benefit to doing inculcation. We’re finding that’s not the case with dry beans,” he said.
“The number that we can physically apply of any inoculant to the seed is not sufficient to get you to maximum fixation. The bacteria have to multiply in the soil.
“What we were finding was the likelihood that this brand of inoculant did not inoculate effectively because it was not multiplying in the soil and, or it just didn’t like that variety,” he said.
Added Shaw: “Across the board we weren’t seeing responses to the inoculants but we were getting responses to the nitrogen fertilizer. So, it’s sending a clear message that this inoculant product was not working in this bean system. It might be the wrong strain that doesn’t affect this type of bean or it might be that this American (North Carolina) strain don’t survive well in our conditions.”
While this is the first year of available data, Hnatowich is cautiously optimistic that future research will cause the dry beans to gain traction as a popular choice for growers.
“The potential is, we could move this from a specialty type of row-crop production to a solid seeded with some strong economic returns for a dryland production, particularly in the areas of the black soil zone right now where peas have got a problem with aphanomyces. With black beans or with beans in general, they are not as prone to the aphanomyces conditions, so it could be a pulse crop that fits into that pulse rotation,” he said.
