Credit: American Crystal Sugar
Three Years of Trials in the Red River Valley
This image from a 2008 Moorhead sugarbeet field shows variable-rate seeding plot yield data (horizontal strip) overlaid on productivity zones that were developed based on satellite imagery and previous crop yield data.
Variable-rate fertilizer application has become commonplace among sugarbeet growers, with the result generally being more-efficient use of fertilizer inputs, more-consistent beet yield and quality across fields — and better per-acre revenue.
How about variable-rate seeding? Could changing your in-row spacing and plant population from zone to zone within a given field translate into more-efficient use of a key input (seed) and, at harvest, produce more tonnage and/or improved crop quality?
* Other American Crystal personnel involved in this project were Curtis Funk, agriculturist in the Crookston district; Joe Hastings, agriculturist in the Hillsboro district; and Allan Cattanach, the cooperative’s general agronomist. ** Moorhead data are from 2008 and 2010; the 2009 Moorhead site was hailed out. Crookston data are from 2009 and 2010. The 2010 Hillsboro study used productivity zones based on topographical mapping. Since the Hillsboro data represent only one year, those results are not discussed here.
That was the question addressed in a Red River Valley study conducted over the past three growing seasons. The project, led by Lynn Dusek, American Crystal Sugar Company Moorhead district agriculturist and member of the cooperative’s precision ag team, sought to determine optimum plant populations for different management zones within several commercial fields. Concurrently, it examined optimum seed spacing trends for high, intermediate and low productivity zones.
Working with cooperating American Crystal growers, Dusek and his group* established studies at six locations within the Moorhead, Crookston and Hillsboro** factory districts. All fields were planted in 22-inch rows, and the growers used recommended agronomic and pest management practices. They likewise used their own harvesters (equipped with yield monitors), while quality samples were handdrawn for each treatment within each established productivity zone.
Productivity zones were established for seed spacing treatments. The zones in the Moorhead and Crookston district fields were based on previous crop yield maps and satellite imagery. “High” productivity zones were denoted by green; “intermediate” zones by yellow and “low” by red.
What were the results from the three study years? Harvest plant stands for the Moorhead and Crookston fields are summarized in the table at left. Three-year trends for recoverable sugar per ton (RST), recoverable sugar per acre (RSA) and revenue per acre are depicted on the three graphs at left.
Here’s the three-year bottom line:
• The optimum in-row seed spacing varied by up to two inches, depending on productivity zone. Specifically, the optimum spacing for the “low” (red) zones was 3.5 to 3.9 inches; for the “intermediate” zones (yellow), it was 4.3- 4.6 inches; and for the “high” (green) productivity zones, 4.9-5.5 inches.
• Plant populations, as would be expected, followed a similar track. The optimum population in the “low” zones was in the 47,-55,000 plants-per-acre range. For the “intermediate” zones, it was 42,-47,000; and for the “high” zones, optimum range was 35,-42,000.
• Harvest losses were greatest with the higher plant populations that were needed in order to maximize yields in the “low” productivity zones.
• The best recoverable sugar per ton (RST) in the “high” (green) productivity zones came with the wider in-row
spacings, while RST was fairly stable across in-row spacings for the “intermediate” and “low” zones (Figure 1).
• Recoverable sugar per acre (RSA) differences were quite dramatic when in-row seed spacing was modified. As
Figure 2 shows, RSA improved significantly with the wider spacings for the “high” productivity zones, while it was
best in the “low” (red) zones with the narrower spacing.
• Per-acre revenue across the four sites for which data were compiled (2008 and 2010 for Moorhead and 2009 and 2010 for Crookston) also showed significant differences (Figure 3). The “high” productivity zones did significantly better with the wider in-row spacings, while the opposite was true for the “low” zones. Revenue from the “intermediate” zones also trended upward as seed spacing was widened.
Dusek says the results to date from the variable-rate seeding trials are definitely encouraging. “We’re finding consistent trends,” he notes. “The results seem to be tracking well with satellite imagery and yield mapping data.” While it’s still early in the process, the sugar company agriculturist believes variable-rate seeding could one day be a common practice that helps enhance both a field’s productivity and the grower’s bottom line. And it could take on added dimensions, such as split-planting of different seed varieties within the field, depending on the productivity zone.
“There is promise,” Dusek affirms, “and we have plans to continue these types of studies.” — Don Lilleboe
Don Lilleboe is editor of 'The Sugarbeet Grower' and 'Gilmore Sugar Manual.'