An intercropped corn-grazing trial at the Manitoba Beef and Forage Initiative (MBFI) is hoping to improve on an already cost-effective way to winter cattle.
Organizers say there’s still some work to do, but the demonstration research farm north of Brandon added yet another year of data to their ongoing study mixing corn grazing with a mixed-species forage intercrop.
Researchers hope the study might help address one of the main issues with corn grazing: grain overload. They’re hoping their refinements can see beef producers spending less time moving hay to the field.
Why it matters: Ration planning is among the most difficult parts of wintering cattle through corn grazing.
While considered a much more affordable option to typical winter yardage — the province’s 2021 cost-of-production estimates for a 150-head herd put corn grazing costs at $1.29 per cow per day for 35 days of extended grazing — cattle’s tendency to go straight for the cobs seriously increases risk of those animals gorging on grain.
Experts currently recommend that producers cross-fence to limit area of access at one time. Animals should be left in the paddock long enough to get good utilization of stalks (typically the last thing on a cow’s preference), and should get a shot of hay right before going into the next paddock, limiting available stomach space.
If cows are eating enough underseeded forage, however, study organizers hypothesized, maybe some of that supplementation can be rolled back.
At the same time, the study is interested to see if adding legumes into the system might improve protein in standing corn.
Like last year, this year’s plots featured a mix of both 30-inch and 60-inch corn row spacings, with wider rows double seeded to maintain total number of plants. Two varieties, grain hybrid Pride A4514RR and the more forage-based Pride AS1037RR, were included in the 2020 study.
Both spacing levels were further divided into intercropped and non-intercropped plots, although even non-intercropped corn had a sort of unintentional intercrop, given that the field in question had serious millet and wild oat challenges, MBFI general manager Mary-Jane Orr noted.
In fact, data from 2020 showed that “non-intercropped” plots still returned significant under-canopy biomass — in some cases, more so than the intentional intercrop.
Plots were then grazed in late fall and early winter. Yield was measured for both corn and the intercrop, as well as quality factors like crude protein and digestible nutrients.
On the most basic level, the study hypothesized that wider rows simply give more room for the cow to fit, and may lead to less plants knocked over. More corn might therefore make it into the animal’s stomach, rather than being trampled.
At the same time, wider rows mean more sunlight, hopefully promoting growth of the intercrop below.
There has, indeed, been more intercrop growth and a difference in corn trample in the wider rows, Orr said. Last year, wider rows saw over three times the intercrop yield in both types of corn tested.
Neither intercrop, nor spacing, significantly impacted corn silage yield in grain corn.
The forage variety, in contrast, showed generally more silage yield across treatments, but the highest yields in both 30-inch spacings (ranging from just under 12,000 pounds per acre on intercropped plots to 14,000 pounds per acre with conventional growing conditions).
“We didn’t see a huge, significant breakdown from having the intercrop in there,” Orr told field tour attendees in mid-August.
Protein results added yet another ripple. Feed tests in 2020 found that, in the grain variety, silage from both 60-inch spacings came out ahead in protein, and intercrops gave protein a boost in the 30-inch rows. Forage variety results, interestingly, showed a spike in protein from non-intercropped narrow rows.
“You might not have the forage, but that intercrop, especially those legumes, are providing a role,” Orr said.
Some of those plants, such as some hairy vetch, then returned this spring for a double benefit, since regrowth was taken for greenfeed.
This year’s version of the study expanded into different corn varieties.
Drought this year put a significant curb on intercrops, Orr noted. Corn itself established well, she said, but soil was dry when intercrops were planted, and remained dry for the next six weeks. That stress was evident in the stubby plants struggling below the corn canopy. Researchers hope that August rains will help jump-start late-season growth.
Last year, plots enjoyed good growing conditions. There was also little snow to dissuade grazing, compared to deeper snow years, when cattle would have to work to access the plants.
Work in progress
The farm has yet to see the productivity needed out of those intercrops to really offset a normal supplement.
“But we see the promise of it,” Orr said. “I think there is an avenue to keep progressing towards.”
Field realties have also complicated simple comparison between intercropped and non-intercropped plots.
Grazing experts, such as provincial livestock specialist Shawn Cabak, will often urge producers to get on top of weed control before starting to corn graze if they want the economics to work out in their favour.
But Orr and MBFI want to test if Roundup Ready corn grazing can help beat back weed pressure.
“We’re trying to utilize all the tools that we have to try and bring our fields back into better productivity,” Orr said. “So we’re using chemical control, both spraying in season and fall, and we’re using timely cutting of the fields — taking it off as greenfeed in the following year — and then we’re also using grazing, so any regrowth after that greenfeed is then grazed again.
“We’re trying to get as much growing (as possible) out of the seed bank, but then just keep nipping it down to get it to a point that what we want growing there is going to outcompete the historical weed seed bank that we’ve had there.”
It is the farm’s hope that the study can get a clean enough slate on that the project can focus solely on ideal agronomy and increasing intercrop yield.
Although she would “love” to work only on fields that are clean, “I think there’s value to being just really transparent about where we have challenges,” as well as the bouquet of tools the farm uses to address them, Orr said.