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Use kernel weight to set rates

To calculate an accurate seeding rate, it helps to know the weight of 1,000 kernels of seed, the germination rate and estimated seedling mortality.

“That is what farmers are after,” says Walter Enns, agronomy manager, Keystone Groups, Cargill Ltd. “When farmers try to optimize their yields on the farm it all starts with their desired plant population. To get that, we have to get the right seeding rates, and getting the right seeding rates comes down to your 1,000 kernel weight.”

Counting 1,000 kernels, then driving to the nearest scale for an accurate weight would make seeding more accurate (or, even counting 100 kernels and multiplying the weight by 10). But few farmers take the time.

Shaun Haney of RealAgriculture.com and a seed grower from Picture Butte, Alta., says precision in seeding is important. Seeding on a bushel per acre basis just doesn’t cut it anymore.

“The variability in seed weight from year to year is something that could seriously affect a farmer’s bottom line, especially in climates that vary so much from year to year,” says Haney.

1,000 kernel weight

Walter Enns says getting the right seeding rates comes down to the 1,000 kernel weight and if he knows that number, it’s easier to calculate a more accurate seeding rate.

Accuracy is key when using the 1,000 kernel rate for wheat, barley, oats, corn, or soybeans. When it comes to canola, Enns says, “You have to remember the elasticity of that plant. If you have the perfect amount of seed in the ground, then you have a plant every square foot, you have the potential of getting a very good crop because of how elastic or how good that plant is at compensating.”

What if there’s 50 per cent plant mortality rate due to various reasons, poor soil conditions, cool growing season and the like, and flee beetle activity, he asks.

Many seed companies include the 1,000 kernel rates right on the bags and have for many years. Even canola seed companies are placing the 1,000 kernel rates right on the bags, he says.

The calculation

For accurate seeding rates, farmers first need to determine the desired plant population, for example ten plants per square foot. Multiply that by the 1,000 kernel weight (in grams). Then, divide that number by the expected seed survival rate (a percentage), and, finally, divide the resulting number by ten.

The desired plant population will vary by crop. Manitoba Agriculture, Food and Rural Initiatives (MAFRI) recommends measuring the 1,000 kernel weight by counting out 1,000 seeds of grain and weighing the sample in grams. Seed weights vary between varieties, fields, crop types and from year to year.

The expected seed survival rate is the expected germination rate, less a small amount for seedling mortality. “For example, under normal conditions, expect approximately 95 per cent germination. However, if planting in unfavourable conditions, like cold, wet soil, expect approximately 90 to 93 per cent germination, as three to five per cent of the viable seed will not produce a plant,” says the website.

“Calculate that and it spits out what your seeding rate should be,” Enns says. “I think it’s fairly straightforward, but I do want to say it is a deeper conversation farmers need to have with an agronomist.”

While not to put a damper on this method, it concerns Enns if farmers simply use the 1,000 kernel weight without knowing all the ramifications.

“I can run examples where that seeding rate is suddenly three pounds to the acre or run examples where that is seven pounds to the acre,” he says. “That might not be the right fit for the farmer considering his equipment and environmental conditions and other external factors.”

Enns thinks more farmers are adapting to this method in cereals, and encourages farmers to visit the MAFRI website to check out the formula and other information (at www.gov.mb.ca/agriculture, type “seeding rate” in the search box).

Canola seeding rates

Enns says canola plants don’t fit the theory as well as other crops.

While canola seed companies include the 1,000 kernel weight on some of their seed bags, Enns cautions farmers to get help on this one. First, looking at the numbers, it could vary between 3.2 grams to 5.6 grams for a 1,000 kernel weight.

“Suddenly my germination could be 90 per cent and seed survival could be as low 50 per cent of that,” says Kehler.

The real world

Ken Panchuk, provincial soil specialist with the Crops Branch of Saskatchewan Agriculture tells Shaun Haney in a recent interview that farmers should consult the manufacturer’s seed chart on their air seeder.

“Some of the new air seeders have seed counters in the tubes, while the new trend is precision metering systems on the air seeders,” says Panchuk.

So why aren’t farmers shifting to this 1,000 kernel weight system?

Panchuk says part of the reason is that it’s very difficult to predict field mortality and weather conditions.

“With the cooler, wetter springs of the last few years, it’s even more difficult to predict seed mortality, and farmers are more reluctant to go with the 1,000 kernel weight because you still have the unknown field mortality that you have to adjust for,” says Panchuk. †

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