Corn Planting Delays: Introduction
The most popular question from customers and prospective customers of CropProphet this year is “how do you account for the corn planting delays in your forecasts of corn yield?” This post addresses that question by looking at the performance of CropProphet in prior late planting years.
May 2019 = Wet in the Corn Belt
At this point in the US crop season, just about everyone knows about the very wet May that occurred and is watching carefully for information regarding its impact. After all, corn planting delays can have a significant impact on end-of-season corn yield and production. The planting delays mean the yield potential is lowered because the crop across the corn belt has less time to accrue beneficial growing degree days.
On a production-weighted basis, corn-growing area weather conditions indicate the United States received 163% of normal precipitation while soybean growing areas received 155% of normal precipitation.
The excessive rainfall greatly increased soil moisture, caused widespread flooding, and prevented producers from being able to plant their crops when they normally do.
2019 Corn Planting Delays
The chart below shows the US corn planted progress from 1990 to 2019. The data is provided by the US Department of Agriculture. The heavy black line is 2019 and the timing of the corn planting delays. There are not many years with similar planting delays in the past 30 years.
We selected five years from this data that represent other late planting years. The years were 1993, 1995, 1996, 2011, and 2013, and these are highlighted in red in the graphic below.
CropProphet and Planting Delays
The CropProphet modeling methodology for corn and soybean yield and production does not directly include the planting progress of each season. However, because the model is weather-based, relationships such as the following are included in the model:
bad weather -> causes planting delays -> shortens growing season -> reduces yield
Numerous other statistical relationships between spring weather and subsequent crop outcomes are also represented. CropProphet, therefore, captures the impact of planting delays on yield because we are quantifying the impact of early season weather via robust statistical relationships across millions of acres of farmland.
With 40 years of historical weather and US crop data available to CropProphet, it is possible to accurately quantify the impact of weather on crops, and as part of the modeling approach, we recreate yield forecasts for prior years. This data is available in our Modeler product option. An artistic rendering of 33 years of US corn yield forecasts is shown below.
Corn Yield Forecasts and Delayed Planting Years
Using the data from the 33 years of daily crop yield forecasts from the Modeler data set, we extracted the corn yield forecasts for the five prior years with corn planting delays to examine the forecast performance, measured as the mean absolute error (MAE) in these years compared to the average MAE performance of CropProphet. The results for the yield and production forecasts are shown below.
In this case, we show CropProphet forecasts from September 7th of each year and compare the result to the subsequent USDA NASS mid-September yield and production forecasts.
Conclusion: Impact of Corn Planting Delays
The conclusion from this analysis is that the CropProphet:
- yield forecasts have been better in previous corn planting delayed years (1.6 bpa mean average error) than in normal years (2.3 bpa)
- yield forecasts during delayed planting years are substantially better than the USDA forecasts in those years
- production forecasts are very similar in skill (198 mm bushels delayed vs 188 bushels all years) in delayed planting years.
- production forecasts are substantially better than the USDA forecasts during delayed planting years
Most importantly, CropProphet forecast skill was not degraded in prior years that experienced corn planting delays, suggesting that the relationship of weather to corn yield is appropriately captured by the model.
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