Variable-rate seeding (VRS) provides farmers the opportunity to match plant populations with productivity zones throughout a field. Zones can vary based on historic yields, soil type, topography, drainage and more. Planting the right number of seeds in the right place in fields has the potential to reduce seed costs and increase yields.
Farmers first took notice of variable-rate technology with lime and fertilizer applications in the 1990s. Fast- forward to today, and adoption of prescription seeding has been slow.
Only 22% of farmers use variable-rate seeding to plant crops, according to the 2022 CropLife/Purdue University Precision Agriculture Dealership Survey. More than 140 national agricultural suppliers -- mostly from the Midwest -- participated.
One reason for the lukewarm embrace of VRS may be due to mixed results from university and industry studies. Some indicate little benefit, while others show significant boosts to yield and profit potential.
Alex Lindsey, an Ohio State University crop ecophysiology and agronomy specialist, has extensively studied VRS with colleagues at Ohio State and other universities. He says the precision-ag tool is a way to improve profitability by a couple percentage points, possibly more in fields with higher variability, such as different soil types and slope.
"I wouldn't bank on buying a new farm with implementing this technology, but farmers can see (yield and profitability) increases," Lindsey says, noting any agronomic and economic boost in today's farm economy is good. "I don't think anything is off the table to consider trying at this point."
Lindsey co-led a study with fellow Ohio State researcher Peter Thomison and Emerson Nafziger, a University of Illinois crop-production professor emeritus. The study estimated return-to-seed of variable versus uniform corn-seeding rates.
-- Find the study at https://ohioline.osu.edu/…
The study, released in 2018, analyzed data from 93 seeding-rate trials in Ohio and 32 in Illinois from 2012 to 2016. The optimum corn-seeding rate -- the one that maximizes profitability -- can vary within and among fields with small differences in soils and weather, the study determined. Seed cost was calculated at $3 per 1,000 seeds and the grain price at $3.75 per bushel. (Commodity prices and seed costs are higher today, which would change calculations and results).
In Ohio, the economic optimum seeding rate or variable seeding rates ranged from 18,000 to 44,340 seeds per acre, with an overall average of 32,129 seeds per acre. The uniform seeding rate for the trials was 32,721 seeds per acre.
VRS trials averaged 205.5 bushels per acre (bpa), or 2.9 bpa better than uniform seeding. VRS also averaged 542 seeds per acre less than uniform seeding. When taking into account the higher yield and less seed, the VRS return-to-seed was $12.53 per acre better than uniform seeding.
In Illinois, VRS was economically better than uniform seeding, but not as much as in Ohio since yield responses were flatter. The uniform seeding rate in Illinois trials was 33,704 seeds per acre with an average yield of 225.7 bpa. The VRS rates ranged from 24,020 to 40,640 seeds per acre (averaging 33,781), with an average yield of 226.6 bpa. The return-to-seed favored VRS by $3.14 per bushel.
"Variable-rate seeding is a tool to potentially help leverage future gains on your farm," Lindsey says.
Typically for corn, seeding rates are increased in high-productivity zones and decreased in low-productivity zones. For soybeans, it's often the opposite. ... rates are boosted in low-productive zones and lowered in high-yielding areas.
"I think it (VRS) has a fit in areas that have a wide range of yield potential," Lindsey adds.
A joint Ohio State University-Michigan State University study released in 2021 compared variable-rate seeding prescriptions and optimum uniform seeding rates for soybeans.
No economic analysis was done, but the study found that adjusting variable-rate seeding populations to achieve a final plant population of 100,000 to 120,000 plants per acre is usually adequate when planting in May to maximize yield.
-- Find the study at https://acsess.onlinelibrary.wiley.com/…
Justin Peterson farms with family near Wyanet, Illinois. He's also a field agronomist with Beck's Superior Hybrids.
The family's row-crop operation, after some coaxing from Peterson, started to variable-rate corn two years ago. Positive results from VRS studies by universities and Beck's were the catalyst, Peterson says.
"Input prices are up. Commodity prices are high. If we can save some money and increase yield (with VRS), we can put a little money back in our pocket or put it elsewhere in the operation," he continues.
Weather issues have limited yield gains from VRS, Peterson admits, but seed savings have occurred. "I won't get into the dollars and cents, but you can save money," he adds.
Peterson estimates only 15 to 20% of farmers he works with through Beck's use VRS. He surmises that doubts about economic benefit keep them from trying the practice even though most of the producers have equipment and technology capable of variable seed prescriptions.
In the future, Peterson will variable-rate seed soybeans and experiment with changing corn hybrids and row widths in fields, along with VRS.
A recent two-year Beck's Practical Farm Research corn trial found that variable-rate seeding (38,000 and 34,000 seeds per acre) and changing row widths (10- and 30-inch rows) to match soil type and other agronomic needs produced nearly $100 more revenue per acre than planting only 30-inch rows at 34,000 seeds per acre.
-- Watch a video about the study at https://www.youtube.com/…
The Iowa Soybean Association offers a soybean variable-rate seeding simulator that uses research data and economic analysis to help farmers determine if the practice is right for them.
-- Find the simulator at https://analytics.iasoybeans.com/…
Farmers upload data such as yield history, which remains anonymous, seeding rates, soybean survival rate, seed costs, soybean prices and more. An online user manual is available to help you use the simulator. It can create VRS seeding prescriptions for farmers.
"The simulator will tell you whether VRS is worth doing on your farm based on field variability," says Scott Nelson, a senior field services program manager and agronomist. "We've seen examples of $25- to $30-per-acre profit advantage from seed savings and higher yields. Our goal is to improve farmer profitability."
VARIABLE-RATE SEEDING TIPS
Michigan State University agronomists offer advice on how to implement VRS on your farm:
-- Identify and understand the field variability that can be managed with different plant populations.
-- Divide a field into "management zones." These zones can be created based on various data layers such as historical yields, soil properties, topography and/or aerial imagery. If using yield data, it's important to use multiple years of data from the same crop that will be planted.
-- Once zones are identified, information on agronomic response to seeding rates can be used to create variable-rate prescriptions. This allows for customized seeding rate in different zones in the field, potentially resulting in higher yield and lower input cost.
-- Conduct on-farm strip trials to observe how yield responds to the seeding rate for each field. Spatial yield analysis can be conducted to help investigate whether VRS has potential to provide a positive return on investment.
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