Variable-rate planting catches on as growers strive to make every seed count with their costly top-flight genetics
Precision agriculture may have got off to a patchy start in Eastern Canada, but one use that is generating a lot of excitement right now is variable-rate seeding. Indeed, the technology to have row units turn on and off automatically seems to have come at exactly the right time,
Higher-priced corn seed may be worth the cost, packed as it is with traits and with the newest high-yield genetics, but it also increases the incentive to make sure every seed performs to its potential.
That can add up to a quick payoff for variable-rate planting, says Greg Millard who sells Precision Planting products and manages Vernon Valley Farms near Osgoode, Ont.
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For example, in a field with an angle you can avoid having all those triangles that get double planted, wasting costly seed. “Those areas that used to get double planted didn’t yield worth a darn,” Millard says. “And if you lifted the planter too soon then you got no corn and the weeds took off.”
Millard says he’s even seen increased weed pressure in the soybean crop the following year due to a buildup up in the weed seed bank in those unplanted areas.
In 2010, three-quarters of the corn acres at Vernon Valley Farm were planted using variable-rate technology. In one trial, corn was planted at rates of 30,000 plants per acre (ppa), 34,000 ppa, or 38,000 ppa, depending on soil productivity zones previously mapped and loaded into Millard’s 20/20 Seed Sense monitor.
These soil productivity zones were based on yield maps overlaid on soil types and were created using Farm Works software. Each field that was planted at a variable rate also had three check strips across all planted zones to compare against the variable rate.
While more years and more test results are needed before firm conclusions can be drawn from these trials, one interesting preliminary result is that the 38,000 ppa test strip had the highest yield and was the most profitable in 2010, an excellent growing year, says Paul Sullivan, certified crop adviser who works with Millard on the on-farm trials.
However, Sullivan cautions that this response to higher plant populations may be a regional effect specific to Eastern Ontario, since others are not reporting similar trends elsewhere.
This effect of higher populations does highlight the potential benefits of carrying out your own population trials to determine optimum planting rates for your land. Since the 20/20 Seed Sense unit records the number of seeds planted, Millard will start making economic comparisons that incorporate the cost of the actual amount of seed used.
Millard also noticed a big difference in how different corn hybrids responded to varying planting rates, which means that hybrid selection is an important piece of the puzzle too.
Dale Cowan, senior agronomist with Southern Cooperative Services, has been working with precision ag since day one, and he cautions farmers to develop a good understanding of the causes of their yield variability before making management decisions.
While it may seem intuitive to reduce populations in areas of a field that are producing poorly, it may actually be the wrong thing to do. Yield can be influenced by many factors including planting date, variety, slope position, depth of topsoil, organic matter, bulk density, pH, soil fertility, and weather, to name just some.
Cowan recommends taking the time to implement side-by-side fixed-rate population trials for direct comparison to pinpoint optimum seeding rates.
Pat Lynch, an agronomist in Stratford, Ont., suggests starting with a very simple approach to varying yields based on your knowledge of your land. For example, you could use two populations: one for expected yields greater than 160 bushels per acre and one for under 160.
Then look at the yield maps and tweak the populations for the next time, Lynch recommends.
Millard and Sullivan also see potential to vary soybean populations. The soils at Vernon Valley Farms vary from muck to silty clay loam. The areas with silt loam soils tend to have more vegetative growth and are more prone to white mould, which has knocked their yields by as much as 15 bushels per acre.
As a result Sullivan created maps so that the areas prone to white mould were planted at the lower population of 100,000 ppa while the areas where beans tended to be shorter were planted at a higher population of 165,000 ppa.
Millard thinks he may be losing a bushel or two of yield in a good year by planting at the lower populations in the disease-prone areas but figures he won’t see that 15 bushel yield hit in a wet year when white mould would be a problem.
Variable-rate seeding appears to be one area that holds promise to improve farmers’ bottom lines. We’re be sure to see many more variable-rate seeding trials 2012 as more farmers adopt this technology. CG
