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Variable-Rate Seeding Shines

Wednesday, January 2, 2013
filed under: Planting Systems

Sometimes, less is more. That’s one very low-tech way to describe the results of Meilon Hildebrant’s experimentation with variable-rate seeding of sunflower over the past three years. But there’s a healthy component of truth in this very simplified summary.

Hildebrant, who lives at Beach, N.D., just a stone’s throw from the North Dakota/Montana border, farms on both sides of the state line. It’s a very arid environment, averaging just 11-12 inches of annual rainfall. While 2011 was an above-average year for moisture in the area, 2012 was just the opposite. Hildebrant has been a 100% no-till producer since 1988 due to the need to retain and utilize his limited moisture as efficiently as possible.

He also farms ground with extreme variability in topography and soil type. “We get sand and silt loam hilltops, we get eroded clay knobs, and we get some heavier clam loams on the bottom ground. The variability is massive,” he affirms.

That sort of variability obviously does not lend itself to a “one size fits all” approach to crop fertility and plant populations. While he’s always known that, the point was brought home forcefully several years ago when Hildebrant was running behind with his row-crop planting one spring and opted to use his air drill to solid seed a sunflower field. The result was, in his words, “a train wreck,” as the hilltops could not support the higher population and ended up being covered by small, spindly plants. Double-seeded sunflower headlands produced similar results.

While recognizing the problem, for years “it was like ‘how do we remedy this’,” other than by cutting populations across the field, Hildebrant recalls. Then — in concert with his crop consultant, Jeran Honeyman — he decided to travel the variable-rate seeding route.

Honeyman already had worked with Hildebrant for several years as they laid the groundwork for a transition to variable-rate application of fertilizer. The extreme variability in his terrain and soils made Hildebrant an excellent candidate for the technology. “Water is king in this area, and topography determines where the water will go,” Honeyman points out. “Where you have water, you have the best yields in his environment, assuming all other needs are met for optimum crop production. His soils are so diverse and variability extremely high, [which is why] VR technology works in his operation.”

Hildebrant has yield maps for his fields dating back almost a decade, along with five to eight years of satellite imagery for a given field. Also, Honeyman now has mapped 95% of Hildebrant’s acreage with a Veris EC cart. (The Veris cart measures the degree of electrical current that soils can conduct, providing an effective way to gauge soil texture variability within the crop root zone.) He likewise utilizes aerial images generated by the National Agriculture Imagery Program (NAIP).

All these data, properly analyzed and interpreted, have provided prescription fertilization and seeding rate formulas for a minimum of five zones within each quarter section. They establish a target yield for the medium zone, and this zone is fertilized and seeded at “standard recommended rates.” For the other zones, they typically then adjust inputs by 10% increments.

When planting sunflower, for example, the seed drop may be 24,000 or more in the lower, higher-potential elevations — but then drop down to 17,000 or even less when seeding eroded clay knobs.

How has it worked out? Results to date have been very encouraging. While Hildebrant’s promising 2010 crop was lost due to early winter snows, in 2011, a year of above-normal moisture, his sunflower crop yielded between 1,800 to 2,200 lbs/ac — several hundred pounds above his historical norm. The biggest impact from variable-rate seeding occurred in one field that contained a very large hill. In the past, that hilltop usually produced no more than 500-600 lbs/ac; in 2011, it averaged around 1,200 lbs. In the bottom ground areas, with their good moisture and higher populations, yields ran 2,300 to 2,400 lbs/ac, with the yield monitor occasionally registering 3,000.

Hildebrant’s sunflower results in the exceptionally dry 2012 season were impressive as well — especially given the minimal rainfall available to the crop. The overall farm average (still being measured as of this writing) was expected to end up in the 1,750- to 1,900-lb range, with his top field yielding considerably more. However, he adds, one important factor was that some of his 2012 ’flowers went in on prevent plant ground with abnormally good moisture carrying over from 2011.

Still, in the end, did using variable-rate seeding in an abnormally dry year — for what is normally an arid environment — underscore its value? Yes indeed, Hildebrant affirms. “Using the VR seeding with the moisture stress issues we experienced this season was, I believe, extremely beneficial,” he states, “not only to maintain a degree of consistency in yield; but also, the overall plant health, resulting in less variability in test weights and seed quality.

“On what we consider our more-marginal soils, the stress was extreme in 2012. Had we overpopulated those areas, I believe it would have resulted in extremely high-stressed plants and severely impacted the integrity of the crop.”

Hildebrant says a corollary benefit to his variable-rate seeding program has been more-uniform plant drydown across the field. “Before, the hilltops — which were overpopulated — produced plants that had small stalks and heads, dried down quickly and were brittle fire hazards,” he says. “Then, in the bottoms, we’d have larger stalks and heads. Those yields were much better; but they’d still be at 19 or 20% moisture when the hilltops were at 7%. Now, the drydown and harvest moistures are much more uniform.”

“By backing the populations off in the lower-productivity soils, we maintain head size and yield without wasting expensive seed,” Jeran Honeyman adds. “I also believe that since stalk strength is improved, lodging will be less of a concern.”

While thus far they have been using a standard scale for determining seeding rates across all of Hildebrant’s sunflower fields, Honeyman expects they’ll be able to fine-tune the system on a field-by-field basis in coming years. “Not every field is as productive as the next on his farm, so I think we can use multiple years of yield data to determine the productivity of each field,” the Bismarck-based crop consultant states. “[Then we can] set higher yield goals for some fields and push populations higher in some of his best ground. And maybe, on some fields that just don’t seem to have those higher-producing soils, we could back off on populations more than we are accustomed to seeing.”

A key ingredient in this venture, Honeyman adds, has been Hildebrant’s “willingness to try new things and not be afraid to fail. He sees where agriculture is going, and instead of playing catch-up, he is taking the lead. He also has the ability and ambition to understand computers and the technology needed to make the systems work — and he is willing to spend the extra money to be sure he has good equipment that is set up to do the variable-rate applications.”

For his part, Hildebrant says simply, “It’s not an entirely exact science yet, but it seems to be working. We just need to keep refining it.” He’s also starting to experiment with VR seeding of wheat. “Maybe the results won’t be as definitive as with sunflower,” he says, “but we believe it’s worth investigating.”

— Don Lilleboe
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