Putting Fertilizer Where It’s Needed

“We’re trying to

match the nutrient

requirements to

the production.”


Last year, about eight million pounds of phosphorus fertilizer – roughly equivalent to 150 semi-truckloads – were not applied on 750,000 acres of cropland in Western Canada.

It wasn’t needed.

Credit Farmers Edge and variable rate technology for the cost saving.

As a form of precision agriculture, variable-rate technology (VRT) enables producers to vary the rate of inputs according to a crop’s needs.

Not only does VRT tell farmers where fertilizer is needed on a field, it tells them where it isn’t.

“We’re trying to match the nutrient requirements to the production,” said Wade Barnes, president of Farmers Edge, a leading VRT service provider.

From its newly opened laboratory in Winnipeg, Farmers Edge analyzes soil samples, crunches the data and comes up with precise fertilizer rate recommendations for specific areas within a field: a little more N, P or K here, a little less there.

Since last September, Farmers Edge has analyzed over 24,000 samples to produce more than 250,000 individual measurements for soil nutrients.

But the analysis starts long before the samples reach the laboratory.

Using remote sensing satellite technology, technicians employ the Normalized Difference Vegetative Index (NDVI) to measure differences in vegetative growth within a field. The heavier the vegetation, the more productive the soil. Those are the areas on which you focus your fertilizer program. There is no sense pouring soil nutrients on a part of a field that isn’t


SHELVES OF SOILS: Farmers Edge lab manager Brooke Drzystek with some of the 24,000 individual soil samples tested since last fall.

productive to start with, said Barnes.

But Farmers Edge doesn’t just use satellite imagery to derive fertilizer recommendations, he added. It also works at ground level. Technicians trace five or six zones in a quarter section and take multiple soil samples from each zone back to the lab for testing.

When the lab analysis is complete, the results go back to the field. Findings are plugged into a computer program and fertilizer gets applied using GPS technology, following variable-rate recommendations.

It’s all a long way from traditional soil testing, which was based on averages. You took core samples in a field, mixed them together in a pail and pulled out a handful of soil. You sent it in for testing and got back a recommendation for, say, 140 pounds of N per acre throughout that field.

Soil scientists often complain many western Canadian farmers never do any soil testing at all. But Barnes says there may be a reason. When Farmers Edge began operating in 2005, it found many progressive growers had given up on soil testing because composite test recommendations were simply not credible. Actual requirements might range from 200 pounds an acre to 30 pounds an acre, depending on the location within the same field.

“Unless you’re going the whole nine yards and being more specific, it’s still just kind of a shotgun approach,” Barnes said.

Farmers Edge estimates only a third of cropland in Western Canada is properly fertilized. Another third is overfertilized and the remaining third is under-fertilized.

While VRT can correct the problem of applying too much or too little fertilizer in the wrong places, the technology is still just catching on. With 650 clients, Farmers Edge, one of the largest VRT providers, covers only about one per cent of the cultivated acres in Western Canada, Barnes said.

Using VRT isn’t cheap. Barnes said the average cost is around $10 an acre – a significant expense for a producer with thousands of acres of crops. But he also said the usual return on investment is three to one.

Another cost is the equipment itself. Since Farmers Edge doesn’t own VRT equipment itself, producers must either buy or rent it. Previously, leading-edge producers with large operations were the company’s main clients. Lately, however, Farmers Edge is seeing more mainstream “dollars and cents” clients interested in getting a return on an investment, said Barnes.

VRT may provide other financial benefits, too. Placing the right amount of fertilizer in the right places can reduce denitrification, which produces greenhouse gases. Reducing greenhouse gas emissions in this manner could enable farmers to sell carbon credits in the future, Barnes suggested.

Don Flaten, a University of Manitoba soil scientist, agreed VRT is a useful technology. But he said its success depends on something non-technological: a farmer’s personal knowledge.

A farmer with years of experience is able to tell a VRT technician how a particular field performs and which areas have greater yield potential than others, said Flaten.

“The producer’s experience is a very, very important part of the technique of putting together a variable-rate fertilizer program,” he said.

“I don’t think we’re ready to farm completely by computer yet.”

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