Lodging in peas was reduced and protein content was higher in the mixes, but questions remain about nitrogen fixation
Pea-cereal mixtures are becoming more common for greenfeed production in Western Canada, but limited agronomic information is available.
Bill Biligetu from the University of Saskatchewan said adding forage peas into a mix with a forage barley or oats can lead to benefits.
“Most people want to add some sort of legume fertilizer so they can increase cereal yield,” he said during a presentation to the Saskatchewan Beef Industry Conference. “However, there is always a concern or a hesitation, if we add nitrogen fertilizer we potentially also reduce nitrogen fixation of the pea crop.”
A study completed two years ago examined seeding rate and nitrogen applications in three different Saskatchewan soil zones.
There were 12 different pea-cereal mixtures with added nitrogen and without, planted in black soil at Melfort, dark-brown soil at Saskatoon and brown soil at Swift Current. Biligetu said the selected sites were generally low in nitrogen.
Monocultures of 40-10 and CDC Horizon forage peas, CDC Maverick forage barley and CDC Haymaker were sown as monoculture crops and in combinations including pea-barley and pea-oats at 100:30 percent of recommended rates, and at 50:50 rates.
Nitrogen amounts were either zero or 60 kilograms per hectare.
The barley and pea-barley crops were harvested at the hard dough stage for barley and the oat, pea and pea-oat crops were harvested at soft dough stage of oats.
“If you’re familiar with silage production, this can be somewhat too late because silage is soft dough for barley and late milk for oat,” Biligetu said.
One year of the two-year trial saw normal precipitation while the second was dry.
The study found that nitrogen application increased yield only at Melfort.
In all cases, the cereal was the major yield contributor, he said. Dry matter yield from pea-cereal mixtures is good even without adding fertilizer because of nitrogen fixation, although these mixtures yielded slightly less than the monocultures.
Biligetu said adding even a small amount of nitrogen potentially reduces fixation by pea crops because the plants will use free nitrogen first rather than spending energy to produce it.
“Nitrogen fixation rate was greater in pea-cereal than in a monoculture pea crop alone,” Biligetu said. “This means when you are growing the mixtures the cereal crop is also using the nitrogen.”
Protein content was higher in the pea-cereal mixtures regardless of the seeding rate.
“Compared to barley or oat, pea-cereal mixtures had greater protein yield because even when we have a very small amount of pea crops in the mixture, we still see quite a significant contribution of protein,” he said.
Producers who have grown 40-10 peas know that variety lodges significantly. Planting it with the cereals allowed it to stand up better and made it easier to harvest for greenfeed, Biligetu said.