Experimenting with variable rate N, P, K and S

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Experimenting with variable rate N, P, K and S Variable rate applications improve yields and profits, and provide good return on investment.
Written by Donna Fleury


Conceptual prescription maps are overlaid on a field.

Since 2005, Farmers Edge has been helping producers implement variable rate fertilizer technology. This practice is gaining momentum and in 2009, Farmers Edge provided prescription maps for more than 650,000 acres across Western Canada. “We’re having great success and seeing a high level of repeatability, which tells us we’re making money for our clients,” says Jay Bruggencate, territory manager for Farmers Edge at Lacombe, Alberta. “Farmers are focused on increasing yields and profits and better utilization of their fertilizer dollars spent, and variable rate applications can provide a return on investment.”

By varying fertilizer application rates throughout the field, farmers can target higher yield goals in good areas and minimize economic losses on poor areas. “Typically on average, we’re finding that about one-third of a field has been getting enough fertilizer, one-third is getting too much and one-third is not getting enough,” says Bruggencate. By using variable rate, nutrients are reallocated in the field, taking away from those areas that have excess nutrients or are saline or poor producing and applying those extra nutrients to areas that have been deficient.

“Variable rate application is very much a technology in its infancy. We’re having good success basing our variable rate zones off infrared satellite imagery and believe it provides the best foundation to start from.”

Bruggencate adds that there are other valid imagery techniques that can provide good information and maps for yield, topography, electrical conductivity and other information that can support the infrared satellite imagery. “We see yield mapping as more of an evaluation tool rather than creating your zone tool.”


Farmers Edge prescription maps are loaded into the Topcon X20 Controller for variable rate fertilizer application.

Darrell Davidson seeding and variable rate fertilizer system near Haynes, Alberta. All photos courtesy of Farmers Edge West.

Setting up variable rate prescriptions is most important for crops that have higher fertilizer requirements, such as canola, wheat or corn and specialty crops such as sugar beets and potatoes. For crops such as pulses that create a lot of their own N, variable rate fertilizer does not provide a very good return on investment. However, some growers are looking at variable seeding rates for pulse crops such as lentils and are finding good value for that application.

“The vast majority of our business is providing prescriptions for farmers’ drills or seeding systems,” explains Bruggencate. “Prescriptions can be provided for a single blended product, but we believe that if a farmer has the equipment capability for individualized commodities or ingredients, he will get a far better return for that system. Even though fertilizer prices have come down from the highs of 2008, this is still something that can help them move forward and make money.”

Darrell Davidson started working with Farmers Edge on variable rate application and prescription maps for his 3000-acre farm at Haynes, Alberta, two years ago. The land is very hilly and lodging in low areas was typically a big problem. They grow wheat, barley and canola and apply their N as anhydrous ammonia and the P, K and S along with the seed through a Flexi-Coil air seeder. “We didn’t really think we would use the variable rate capability on the air seeder when we purchased it a few years ago,” says Davidson. “But we’re glad we have the technology and are very pleased with the results across the farm. We got much better results in the first year than I thought we would, and the second year was even better. Our yields have improved and protein levels have also improved, with barley making malt quality in each of the last two years. And our lodging problem has been solved, the crop is now standing where we want it to.”

Process not complicated
Davidson notes that although the system looks complicated, it really is much easier than it looks. He uses a Topcon X20 Controller, which has the Farmers Edge prescription maps loaded for controlling the variable rate fertilizer application. “Overall, we use about the same amount of fertilizer inputs, but just move it around to the appropriate zones,” says Davidson. “It does require a bit more soil testing for the various zones, but with the high fertilizer prices, I made my money back in the first year. Even with lower fertilizer prices, the payback on your investment would be about two or three years.”

To get started in variable rate all depends on the type, and in some cases, the colour of equipment a grower has. “A lot of farmers already have the equipment to do this and are not far away from having it set up,” says Bruggencate. “Some farmers think it requires a massive investment and are surprised how little they might need to get started.”

For farmers using a single-ingredient system such as anhydrous ammonia or liquid fertilizer for example, Farmers Edge can set them up with an inexpensive mini laptop in the cab of their tractor and some software for an investment of around $2500. “Each kind of equipment has different price tags and requirements to get going, and more complex systems will require a higher investment.”

Farmers Edge continues to develop new applications in conjunction with their clients including cost per bushel mapping. “We can help farmers calculate their costs, application rates and returns for each zone,” explains Bruggencate. “We’re also working on near-real time or weekly imagery through the growing season that will help with other variable rate applications for fungicides, desiccants and other in-crop applications.”

Another new development is 3-D imagery, which will provide a better understanding of the relationship of topography and zones.

“There are lots of options out there so definitely do your homework and establish a team to work with,” adds Bruggencate. “I wouldn’t recommend jumping on the first thing you see. Very few farmers can do it on their own; you really need a team on your side for both the equipment and agronomics to make it all work successfully.”

Variable rate applications improve yields and profits, and provide good return on investment.