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SoyMAP soybean variety decision support software now available
Author: Arkansas Row Crops

By Larry Purcell, Crop Physiologist, Department of Crop, Soil, and Environmental Sciences, Division of Agriculture, Fayetteville

A 3-year experiment across six states supported jointly by the Mid-South Soybean Board and the United Soybean Board evaluated the response of maturity group (MG) 3 to 6 soybean cultivars to planting dates under irrigated conditions. Results from this experiment were used to create a decision-support tool that determines the best MG to plant at any given planting date across the MidSouth production region. At each of the 10 locations in the experiment, there were four planting dates. The first planting date corresponded to the earliest date that soybean could be planted at a specific location. The last planting date corresponded to a typical double-crop date, and the two middle dates were spaced evenly between the first and last date. There were four cultivars within each MG, and over the 3 years and 10 locations, we collected data on over 6000 observations.

We coupled the experimental data with weather data from each location to calibrate the crop simulation model CropGro. Using the calibrated CropGro model, we predicted yield, crop development stages (R1, R5, and R8), and irrigation requirements for 11 locations between Baton Rouge, Louisiana and Columbia, Missouri. CropGRO predictions included 30 years of weather data for each location, 14 weekly planting dates from mid-March till June 30, MGs from 3 to 6 (in one-half MG increments), for both silt-loam and clay soils. All total, there were around 74,000 individual simulations.

Soybean Maturity, Analysis, and Planning (SoyMAP) is a decision-support tool that can help producers identify the optimum MG to plant at their location for a given planting date based upon the long-term CropGRO predictions. Users use drop-down menus to select location, planting date, soil, and two different MGs that they wish to compare. SoyMAP then provides yield, irrigation requirements, crop development stages, and economic comparisons between the selected MGs.

SoyMAP runs in Excel and can be downloaded at:

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