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With variable-rate technology, your goal is to give extra fertilizer to the most productive parts of the field. It is not about forcing every acre to produce the same yield
By Lee Hart
Pat Kunz says he will never go back to a single-rate fertilizer application over his 2,300-acre farm in southern Alberta. Meanwhile neighbour Cam Schmatlz has adopted more of a wait and see attitude when it comes to the benefits of variable-rate fertilizer technology on his 2,100 acres.
Both producers, who farm near Bieseker, just northeast of Calgary, do agree the concept of applying the most fertilizer where it will do the most good makes sense.
These farmers have worked with southern Alberta agri-service provider DynAgra to adapt their operations to variable-rate fertilizer (VRT) application. You will find VRT service providers across the Prairies. Talk to your neighbours or ask around at farm shows this winter to find one you can work with.
Kunz, who runs a mixed farming operation with his father Chris and brother Kevin, outfitted a new seeding system in 2007 with variable rate technology. He figures he is probably using less fertilizer than he was before, he knows that what he does apply is being used more efficiently, and he expects over the next year or two that a clear pattern of improved yields will emerge.
Schmaltz, who is the fourth generation on the family farm, also expects improved efficiencies, but after a poor trial year in 2007 and a cool, late spring in 2008, he still wants to see yield results for more consecutive years. He does like the fact that he’s getting more soil sampling as part of the VRT service, and it is also more convenient for him to use DynAgra’s custom fertilizer application service.
DynAgra, headquartered in Bieseker with four southern Alberta outlets, has provided crop inputs and agronomic services to producers for years. Three years ago, the company launched its VRT service.
“The idea isn’t to necessarily reduce crop input costs, although that may happen,” says Garth Donald, senior agronomist for DynAgra. “The objective is to improve fertilizer efficiency and increase crop yields.
“Over any field there can be a variation of soil types and perhaps for several reasons there can be a variation in yield. With VRT technology, we’re not trying to adjust fertilizer rates so every acre produces the same yield. The goal is to apply fertilizer at the proper rate where it will do the most good.”
DynAgra’s approach, when it comes to fertilizer, is that there’s no point in flogging a dead horse. Pumping fertilizer to dry, thin soiled, unproductive ridge tops, or lower lying saline soils, for example, isn’t going to dramatically increase yields on those sites. On the other end of the scale, applying high rates of fertilizer to the most productive sites in a field, can increase the risk of crop lodging and yield loss.
That’s essentially what happens when a blanket fertilizer rate is applied to a field. Poorer soils continue to under perform, better sites over perform. With VRT the objective is to apply optimum rates to sites that will produce optimum yields.
“The fertilizer prescription may not reduce the amount of fertilizer applied, but it puts the proper rate where it will do the most good,” says Donald. “You are still going to put some fertilizer on the low productivity sites, but there is no point in putting as much there as you do on the better sites. You are better off to increase the rate of fertilizer on the medium sites and increase yield there.”
START WITH SOIL TESTS AND YIELD MAPS
DynAgra uses several tools to develop fertilizer prescriptions specific to individual farm fields. They take soil tests from several sites over a field, they use yield mapping history generated by combine yield monitors, and they also use remote sensing. Remote sensing uses a satellite photo taken during the growing season. This photo records the amount of energy reflected or emitted from the earth surface. If, for example, you had a crop growing on a field that had varying amounts of biomass — leaf area — due to topography or different soil types, that variation would show up on the remote sensing photo.
DynAgra puts that information together to identify five different production zones in a field — areas with low, medium-low, medium, medium-high, and high yield. With a computer program, the company produces a colourcoded map showing where those production zones are in a field.
From there, DynAgra writes a fertilizer prescription to apply the optimum amount of fertilizer to match the yield potential of each site .
For a simple example, a 150-acre field has all five of the production zones noted above. Each zone is 30 acres. Using a conventional one-rate fertilizer system, you might target a 50 bushel per acre yield for that field and apply 40 pounds of nitrogen per acre over the whole field.
The problem is, the low and medium low yield sites get the same 40 pounds of nitrogen but they only produce 30 or 40 bushels per acre, says Donald. “So in essence you have wasted some of your fertilizer. On the other hand on the medium-high and high producing sites, you applied 40 pounds of nitrogen, and achieved your 50-bushel yield, except that those sites had potential to produce more than 50 bushels. “
In one example given on DynAgra’s website at www.dynagra.com,that 150-acre field given a single-rate of 40 pounds of nitrogen per acre, yielded 6,600 bushels. By reducing the amount applied to low producing sites and applying that fertilizer to the medium and high producing sites, overall yield for that field increased to 7,500 bushels. The same amount of fertilizer was applied, but it was used more efficiently to tap into the yield potential of field.