Intercropping study reveals benefits

SWIFT CURRENT, Sask. — Early results from a study of intercropping in organic systems show some benefits.

Myriam Fernandez, researcher at Agriculture Canada’s Swift Current Research Centre, told a recent low-inputs and organic workshop that a couple of combinations worked to reduce weed seedbanks and produce a higher yield.

The study was initiated to improve the sustainability of organic systems. The last few years of high moisture, even in the semi-arid area around Swift Current, have caused significant disease pressure, Fernandez noted.

High levels of fusarium and aphanomyces have affected pulse crops in all production systems, she said, and intercropping with species that are less susceptible might help.

The trial involves planting an intercrop mix one year, followed by a cereal cash crop the next, and repeating that.

An attempt at the trial in 2016 largely failed due to flooding, although while the legumes in the mix died the companion crop was harvested.

In 2017, the trial looked at different seed ratios of lentils with yellow mustard, field pea with oats, soybeans with flax and lentils with fall rye. Monocrops of each were also sown for comparison.

Two intercrops didn’t perform well.

“Unfortunately, we didn’t get any control of the weeds when we combined the lentils with fall rye,” Fernandez said. “We were kind of disappointed.”

Most of the lentil seedlings died, likely due to allelopathy for which fall rye is known. Allelopathy is a natural chemical effect some plants have on others that affect growth and development.

Also, severe drought last year caused soybeans to grow poorly, but the trial still showed that a higher proportion of flax led to lower weed density than in flax alone. Fernandez said that suggests the soybeans had some impact, even though they didn’t grow well.

The best combinations were lentil-mustard and pea-oats.

“We determined that three-quarters of lentils and three-quarters of mustard would be the best, based on one year of data,” Fernandez said.

“Half a rate of oats and a full rate of peas was the best. Although, a quarter rate of oats also had some advantages in terms of revenue and thousand-kernel weight.”

The lentil-mustard combination at those rates yielded the highest, aside from the monocrops, and brought in the highest revenue based on October 2017 prices. It also suppressed weeds better than either the monocrop.

The pea-oat combination saw reasonably good yields and revenue but did an impressive job of controlling weed seeds. Also, the thousand kernel weight measurements for the oats in all the intercrops were higher than oats alone.

Fernandez said the benefits of intercropping identified after one year include lower seed banks when compared to the nitrogen-fixing crops alone, higher combined grain yields and revenue than in at least one of the monocrops, higher thousand kernel weights for oats, and the insurance against the damage or failure of one crop, as seen in 2016.

She is still analyzing the impact on grain protein and Canada thistle and the quality of soil nitrogen and phosphorous this spring.

The test sites saw little disease last year, so the effects of intercropping on disease suppression are still unknown.

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