15 November 2018

The Gro US Corn Yield Model finished the 2018/2019 crop year on a bullish note, with our yield of 177.4 bu/ac contrasting with the USDA at 178.9.  Our model uses numerous satellite- and ground-based data series to approximate the crop situation, but omits the survey-based and subjective elements of the USDA's process.

About the US Corn Model

Due to the USDA’s excellent data availability and quality, we at Gro decided to model US corn yield first. We applied our agronomic expertise to select the best variables to model corn yield on a county-by-county basis. Then we tested our selections on the 918 most relevant counties separately instead of just on one national number. We performed a “leave one year out” analysis as well, for example, fitting a model to “forecast” 2011 using every year between 2000 and 2016 except 2011. As a result, our backtesting process ran fifteen times on each of the counties. The variables selected by our experts include:

  • Normalized difference vegetation index (NDVI)
  • Land surface temperature (LST)
  • Rainfall data (TRMM)
  • Crop condition surveys
  • Crop calendars
  • Acreage planted and harvested
  • Soil surveys (gSSURGO)
  • Cropland data (CDL)

We applied machine learning/artificial intelligence techniques to the mass of chosen data to estimate NASS county yields, which are reported by USDA each year. Then, using reported harvested acreage data, we aggregated the resulting county yields up to the state and national levels.

Running live for the first time in 2016, the resulting set of models generated results of a higher quality than the USDA’s own estimates, at earlier dates. This is particularly impressive given that the USDA is merely attempting to estimate its own final yield number.

We have made our weekly forecast and commentary during the season available publicly on this website. If you are a subscriber to the Gro data platform, you can access daily forecasts as well as monitor specific inputs to the model (e.g. weekly NDVI updates, daily temperature shifts). For more technical information, you can also download our yield model paper here and watch recordings of webinars we have previously hosted about the model:

Intro to Gro’s Yield Forecast Model

A Technical Lens into Gro’s Yield Forecast Model

Download our US corn yield model paper
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