Operational Test Using Weather Data to Forecast Corn Ear Weight, 1988

Final average weight of grain per corn ear was predicted from weather models for the 1988 August 1 Crop Report for each of the ten States in the National Agricultural Statistics Service's (NASS) corn objective yield program. The daily weather data required by these models was obtained by the NASS State Statistical Offices from the National Weather Service, National Oceanic and Atmospheric Administration. These forecasts were prepared using daily weather data from May 1 through about July 25. For most States, the models was [were] developed from nineteen years (1967-86, less 1970) of final corn ear weights and weather data. Parameters were estimated from data through 1987. On the average, the weather models provided better predictions of final ear weight than did the regular objective yield procedures. However, when farmer reported crop conditions (non-probability sample and judgment type questions) are used to adjust the regular objective yield indications, the adjusted objective yield models outperformed the weather models. This was because the weather models did not fully consider the effects of extremely hot dry weather in late May and June of 1988. Further research into weather models is recommended. This would include the use of early season weather data in forecasting the average number of ears per stalk as well as average weight of grain per ear.