Natural Farming System’s team shares findings of two-year seeding trials

Researchers have examined how seed size affects a crop’s vigour under organic management. Photo: Laura Rance

University of Manitoba trials over 2015 and 2016 looked at effects of saved seed size, seeding depth, as well as differences between varieties and seeding rate for wheat, oats and barley if there was any interaction.

By Lorraine Stevenson
OrganicBiz staff

Organic farmers can produce higher yielding wheat and barley crops with fewer weeds using larger seeds planted at higher seeding rates, according to results from research trials conducted over two years at the Ian N. Morrison Research Centre in Manitoba.

Trials were conducted in 2015 and 2016 to investigate what difference seed size could make on crop yield and biomass, weed biomass and dockage. Other trials looked at how seeding depth and seeding rates also affected yield.

We found that increasing your seeding rate does make a big difference in yield. – Michelle Carkner

For the seed size trials, they used saved seed lots from organic farmers, sieving each lot to figure out what percentage of the seeds were small, medium and large, said Michelle Carkner, co-ordinator of University of Manitoba’s participatory plant breeding program, who worked on these trials with Keith Bamford, technician and Katherine Stanley, a research associate at the University of Manitoba.

That trial shows larger seeds tended to produce wheat and oat crops with higher yield and lower weed biomass. They did not see a consistent pattern with oats.

Notably, the trial also showed the majority of seed is of the larger dimension, Carkner said. “So if farmers have the ability to sieve out smaller seed size then we would recommend that,” she said.

The second trial looked at seeding depths. That trial did not produce findings consistent enough to make any recommendation on depth, Carkner said.

“We did see that the shallower seeding depth resulted in a higher yield in some cases but not in all,” she said, adding their main recommendation is that it is better to seed deeper where the seed can reach soil moisture.

In separate trial they also compared varieties and seeding rates to determine whether increasing seeding rates produces a yield difference.

“We found that increasing your seeding rate does make a big difference in yield,” she said. For wheat they saw a 12-bushel an acre yield increase when increasing from 150 plants per meter squared to 350 plants per meter squared or m2.

For barley, they achieved a nine bushel per acre boost with the highest seeding rate. For oats they also saw a 12 bushel difference with higher seeding rates.

They found that the variety AC Tradition, the first organically bred and registered wheat variety on average yielded significantly higher — 28 per cent better — than the rest of the varieties tested.

Seeding rate calculators are available on Manitoba Agriculture’s organic site so farmers can convert plant population densities to pounds per acre.

Carkner noted that these trials with lowering and increasing seeding rates did not affect seed size. “You can increase your seeding rate and you won’t have a size penalty at the end of the day,” she said.

More details about these trials will be posted online. The filmed presentation can be watched on YouTube. The link to the video is on the Manitoba Organic Alliance website under ‘Presentations’ on its homepage.