Fall field work for canola growers

Clubroot galls can be scouted after harvest, but they will start to degrade quickly.

Swathes blown by wind before harvest will increase the volunteer seedbank. If possible, leave these seeds on the surface this fall to germinate or be eaten.

A long fall provides a few extra weeks to look back on the year that was — to reassess plant stands, fertilizer rates and disease levels. A long fall also gives growers an opportunity to control weeds and distribute residue in fields planned for canola in 2013.

1. Check your plant stand

Field surveys in Alberta in 2011 found that only 54% of canola fields averaged 5 plants or more per square foot, and only 28% of fields had a stand with consistently 5 plants or more per square foot. The ideal plant stand is a consistent 7 to 14 plants per square foot, and anything below 5 plants is not reaching its yield potential.

“If a fall stem count shows fewer than expected plants, growers could look back on the season to see why their stand was so low, and take possible measures to increase seed counts and plant survival for next year,” says Angela Brackenreed, Canola Council of Canada (CCC) agronomy specialist for Manitoba.

To do a stem count, growers can (1) count the stems per metre of row. Take that number and multiply by 100 then divide by the seed row spacing in cm to get plants per square metre. For example, 25 plants per metre multiplied by 100 then divided by 25 cm (10” row spacing) is 100 plants per square metre. Divide by 10 to get plants per square foot. Another way is to (2) use a hoop with an inside diameter of 56 cm. This is equivalent to 0.25 of a square metre. Count the stems inside the hoop, and multiply by 4 to get plants per square metre. Then divide by 10 if you want plants per square foot. Repeat counts a few times throughout the field.

2. Volunteer canola management

Canola crops leave an average of 2-3 bushels per acre of seed in the field, or at least 20 times the seeding rate. Swaths flipped and rolled by heavy winds can increase this number significantly. Leaving seeds undisturbed so they germinate in the fall or get eaten by birds and insects is a good way to reduce the volunteer seedbank. When tillage is necessary, hold off for a few weeks if possible to allow predation and seed germination before seeds are buried. Burying the seed can induce seed dormancy, keeping that canola seed viable longer in the seedbank, possibly for years.

3. Soil tests

With soil analysis results in hand before winter, growers have more time to plan their fertilizer program for next year, to order fertilizer, and to take advantage of reduced pricing opportunities that may occur. For fall results that most closely predict spring residual levels, the ideal time is to take samples when soil temperatures drop below 7 C.

“On the other hand, sampling right after combining can indicate whether this year’s crop had enough nutrients,” says Dan Orchard, CCC agronomy specialist in Alberta. “If the soil is drained, growers may see this as a reason to consider higher nutrient rates for canola fields next year.”

4. Weed management

Post harvest is a good time to control winter annuals, biennials and perennials. For best results, weeds must be actively growing with new supple leaf area to target, so give time after harvest or frost for plants to recover. Ideally, you want to apply at a time when temperatures are above 10 C and rising on days with predicted highs above 15 C but preferably higher. Sunshine is as important as temperature. If applying on days where temperatures are at the minimum, it is critical that the sun is shining brightly.

“Not many products are registered for fall use ahead of canola,” says Tiffany Martinka, CCC agronomy specialist in Saskatchewan, “and with the dry conditions this fall, the risk of carryover might be higher for any residual product.”

5. Residue management

Spreading residue evenly across the field is critical for accurate and consistent canola seed placement next spring. If the combine didn’t do a good job, harrowing dry straw is an option.

“However, if you’re considering harrowing and your soils are very dry, you may want to balance the residue spreading benefit against the potential loss of snow retaining stubble,” Brackenreed says. “Aggressive harrowing can often rip out standing stubble, which is actually the best kind of crop residue. Standing stubble holds the snow, prevents soil erosion and is off the soil surface and out of the way for drill openers. Chopping down all the standing stubble just adds to the matt of residue on the soil surface.”

6. Scout for clubroot and blackleg

After harvest, growers can clips stems to check for blackleg and carefully dig up roots to check for clubroot galls, but don’t wait too long. Clubroot galls will break down fairly quickly after harvest, but the week after combining can be a good time to dig up stems to check for presence of the disease. Clubroot continued to spread to new areas in 2012. Growers who discover clubroot early can use a combination of machinery sanitation, crop rotation and variety selection to limit its spread and impact on future canola crops.

For blackleg scouting, cut stems just above the root crown to look for darkened stem tissue. Ideally, this should happen within a few days of harvest. As the plants die, other decay may look like blackleg and confuse the diagnosis.

This media release is supported regionally by:
Alberta Canola Producers Commission; SaskCanola; Manitoba Canola Growers Association; Canola Council of Canada; Peace River Agriculture Development Fund; B.C. Ministry of Agriculture & Lands.