Find the Soybean Sweet Spot

March 5, 2016 02:49 AM

What maturity group and planting date will give optimal yields?

Where is the elusive seam between low risk and big yields? A new decision-support tool dramatically cuts away soybean guesswork and conjecture at planting. Soybean Maturity, Analysis and Planning (SoyMAP) helps farmers identify the optimum maturity group to plant at a given location for a particular planting date. SoyMAP highlights planting date and maturity group combinations to target the sweet spot between minimum risk and maximum yield.

 SoyMAP’s decision-support tool  helps farmers find the right soybean  maturity group at planting. 

Three years of field study and a year of data analysis by Larry Purcell, professor of crop physiology, University of Arkansas, and his team provided the footing for SoyMAP. Purcell’s team planted Maturity Groups III through VI on irrigated ground across 10 locations in Arkansas, Louisiana, Mississippi, Missouri, Tennessee and Texas. Four different cultivars were planted within each maturity group. The earliest planting took place as soon as permissible in spring; the latest planting started the last week available to double-crop in a given location. In total, results were collected on 6,000 plots.

Purcell used narrow rows, with the widest at 30". Most locations were twin row or 20" spacing. All locations measured yield, seed quality, developmental stages, stand counts, plant height, node number, lodging, shattering and green stem. Maturity Groups IV and V consistently recorded the highest yields—a definite message to plant early. Purcell was surprised by late planting dates, however. The highest yields came from Group IVs and some Group IIIs, contrasting with the convention of matching a late planting date with late-maturing cultivar.

“We’ve used our research results, combined with 30 years of daily weather data from the sites, to come up with SoyMAP,” Purcell says. “The power of the model lets us look at historical weather data and predict what the yield was for different maturity groups, planting dates and different locations. The simulations offer concrete data to determine what the best choice maturity group is for your location on a particular planting date.” 

Users access pull-down menus to select location, planting date, soil and two different maturity groups they wish to compare. SoyMAP then provides yield, irrigation requirements, crop development stages, input costs and economic comparisons between the selected maturity groups. In total, with weather history, 74,000 simulations were used to create SoyMAP. 

Michael Popp, professor of agricultural economics and agribusiness, University of Arkansas, created SoyMAP’s online spreadsheet platform. 

“SoyMAP doesn’t look like a spreadsheet and no special software is required,” Popp says. “There are already online tools showing phenological data, but nothing as extensive on risk analysis and economic meaning as SoyMAP.”

The decision tool is available online and can be downloaded for free at “It’s simple to use and easy to understand,” Popp adds. “The idea is for a producer to plan out the planting season and select among planting dates and among maturity groups to make a decision that will get them the most money.” 


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Spell Check

Larry Purcell
Fayetteville, AR
3/14/2016 04:51 PM

  There is a youtube video that explains how to use SoyMAP:


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