The CropProphet forecasts for U.S. soybeans have seen little overall change in the past two weeks, as the most likely U.S. yield remains slightly above the long-term trend (see figure below). Both the yield and production forecasts are very close to the July 12 USDA estimates, and there is no indication of whether upward or downward revisions are more likely in the August 10 report.
Rainfall has been highly variable across the Midwest in recent weeks as systems of thunderstorms have affected certain areas while other regions have remained dry (see figure below). Unusual dryness has continued in most of Iowa, and soil moisture is now significantly below normal in at least half of the state. However, very heavy rain occurred recently over eastern Iowa, northern Illinois, and southern Wisconsin, and fairly widespread rains in South Dakota brought some drought relief.
The primary influence on the CropProphet soybean forecast continues to be the positive satellite indication of the crop’s vitality across most soybean growing areas. The figure below shows that the vegetative health index is well above normal nearly everywhere east of central Nebraska and the central Dakotas, and this is a major improvement in comparison to last month. The end-of-season soybean yield is moderately correlated with the satellite NDVI index in July (see the second figure below), and therefore CropProphet relies significantly on the satellite data to forecast the crop outcome at this time of year. Additional predictability is derived from weather and soil moisture data, as well as USDA crop condition reports, and these additional predictors become more important in August as sensitivity to rainfall increases. It is interesting to note that the correlation between soybean yield and NDVI does not improve in August, despite the crop moving closer to maturity, and therefore it is essential to model the direct influences of weather and soil moisture in order to arrive at an accurate yield forecast. CropProphet’s county-level models use an optimal blend of predictors that varies by crop, location, and time of year.
The next update to the soybeans commentary will occur on August 15.