Uniform Stands Yield Better

Stand establishment has been the single most important agronomic and economic issue in canola production over the past 10 years. With increasing seed costs growers have moved towards lowering seeding rates to a point where there is very little margin for error, especially if seeding conditions are not ideal.

It all starts with the seed. Seed size and vigour are key factors in the number of seeds that survive to make a viable stand.

But good seed is just step one. Growers have a lot of influence over what percentage of seed — even good seed — grows into a healthy crop. Timing is one thing. With growers adopting earlier seeding, environmental conditions are less than favorable for rapid even emergence. This is especially true when soil temperatures are 8C to 10C. With early seeding, you want to be shallow and you probably want to make sure you’ve got seed treatment.

Here are some other major factors to consider in improving your canola stand establishment:

SEED AT 4 TO 5 MPH

Under normal to above normal spring seeding conditions — with decent moisture up to the soil surface — increasing seeding speed to five mph, up from four mph, makes almost no difference in the number of seeds that grow into plants. But Canola Council of Canada research has shown that seeding above 5.5 mph can reduce established plant stands by over 50 per cent.

Ideally you want at least 80 plants per square metre — or about seven plants per square foot. And to get full yield potential from those plants, you want them to emerge uniformly throughout the field.

Less than normal moisture makes this worse. In wet years, on the other hand, speed is less of a factor unless canola seed ends up on the soil surface.

In a 2005 study, the Canola Council compared seeding speeds of four mph and 5.5 mph. The target stand was nine plants per square foot. At the higher speed, the stand was reduced 25 per cent compared to the stand from seeding at four mph.

High speed becomes a factor in seed placement. Shank vibration results in uneven seeding depth. And at high speeds, drills encounter a “front to back effect” where soil from the front shanks is thrown onto the second, third and fourth shanks, burying the seed when packed. When canola seed placement is uneven, the seed placed deeper often doesn’t have enough energy in the seed to push up to the soil surface. It’s also exposed to soil pathogens for longer. It most cases, that seed does not grow into a viable plant.

With the plant stand reduced 25 per cent at the higher speed, this equates to one pound per acre of extra seed needed achieve the same plant population. If you have 800 acres of canola, and if canola seed is $6.25 per pound, you could save $5,000 in seed costs by slowing from 5.5 mph down to four mph.

Here’s how it breaks down in terms of time: If you have a 36-foot drill, at four mph you can seed 17 acres per hour. It will take you 59 hours to seed 800 acres. At 5 mph, it will take you 47 hours. So you save 12 hours by going faster, but you need $5,000 more seed to get the same plant stand.

WATCH YOUR FAN SPEED

Growers often run their fan speeds too high. This is often related to ground speed and higher rates of granular fertilizer being applied. As seeding speed increases, you may need to crank

up the fan speed to keep the seed and fertilizer flowing to the openers at the desired rate. With seed moving faster through the drill, impact speeds at manifolds and at the opener can damage the seed. Damaged seed doesn’t germinate.

Depending on the machine fan setup (one fan with dampers or two separate fans), closing the seed damper or reducing fan speed will give you a significant improvement in seed integrity.

A simple “tube sock” test will determine seed damage. Attach a tube sock to the farthest outside seed hose and driving at the desired speed for at least 250 feet. The photo compares canola seed leaving the seed boot at various fan speeds. You can see that at a fan speed of 3,850 rpm, damage is considerable.

REPLACE WORN OPENERS

To replace all the openers on a drill can be expensive, so it makes sense that growers will use worn openers for “one more year” before replacing them. This has its own costs, especially for openers that place seed and fertilizer on separate shelves in the soil. If the seed opener is worn out, you’ll get seed dropping into the fertilizer row — which is too deep, for one thing, and can be toxic to the young seedling depending on the actual nitrogen rate.

MEASURE YOUR SEED SIZE

This will give you a better indication of the required seeding rate to achieve your target plant stand. To size your seed, take 1,000 seeds and weigh them. That gives you a thousand seed weight, or TSW. Then use this formula to determine your seeding rate:

Seeding Rate (pounds per acre) = [9.6 X desired plant density X TSW] estimated seed survival

Insert your own figures. Make sure plant density is given as plants per square foot, TSW is in grams, and estimated seed survival is given as a per cent, expressed as a whole number (as in 75, not 0.75)

Let’s say your desired plant density is eight plants per square foot, your TSW is 4.8 grams and your estimated seed survival is 75 per cent. You’d fill in the blanks like this and come up with a seed rate of 4.9 pounds per acre:

[9.6 X 8 X 4.8] by 75 = 4.9

HOW TO ESTIMATE SEED SURVIVAL

Weather and environment combined with seed management practices are the two key factors that impact survivability. On average, seed survivability is between 50 and 65 per cent across Western Canada. Hybrids are at the higher end. But it relates directly to seed size. Larger seed has consistently higher germination percentage at seven days and higher plant establishment 21 days after seeding. (This is based on a Saskatchewan Canola Development Commission study carried out by Bob Elliot.) The larger the seed size, the more vigour the seed will have.

Better genetics — hybrids, especially — combined with larger seed size (TSW above 4.5 grams), slower seeding speed (below 5 mph), accurate seed placement (good openers), and warmer soil temperature (above 8C at soil depth of 1.5 inches), all increase survivability. The premise is to place as many seeds at the right depth, under the best environmental conditions to increase survivability.

My field experience tells me a grower using good openers (this would include newer low disturbance openers), hybrid seed, seeding into soil with an average temperature above 8C (mid-morning and late-afternoon), and seeding at about 4.1 to 4.5 mph under good soil moisture conditions would have a survivability rating of at least 75 per cent.

A GOOD UNIFORM STAND EQUALS HIGHER YIELD

We’ll summarize this article with results from a three-year study by S. V. Angadi, a research scientist with Agriculture and Agri-Food Canada in Swift Current, Sask. Angadi looked at a range of uniform plant populations from five to 80 plants per square metre (0.4 to seven plants per square foot) and he also looked at patchy or “thinned” non-uniform stands of 10 to 80 plants per square metre (0.8 to seven plants per square foot.)

He found that if you have a uniform stand — if emergence is fairly consistent throughout the field — reducing the plant stand from 80 to 40 plants per square did not reduce seed yield. But reducing the stand from 40 down to 20 plants reduced yields 20 per cent in normal yields and up to 36 per cent in stress years.

In non-uniform crops, seed yield was reduced 17 to 26 per cent when the plants stand dropped from 80 to 40 plants per square metre. Yields for stands of 20 plants per square metre are 23 to 56 per cent lower than yields for stands of 80 plants.

The conclusion is that getting a minimum 40 plants per square metre to emerge is important. Ideally you want more like 80 plants per square metre — or about seven plants per square foot. And to get full yield potential from those plants, you want them to emerge uniformly throughout the field.

The Canola Council has found that yield response curves show the least amount of variability with a stand between seven and 14 plants per square foot.

David Vanthuyne, based in Watrous, Sask., is an area agronomist for Pioneer Hi-Bred.

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