Crop Yield Forecasting

1.4. How do these different forecasts compare? Purpose, coverage,
scale and harmonization issues, and accuracy
At national level, there is only the USDA-NASS’ official crop yield forecast system. The
statistical data are adjusted monthly, on the basis of filed surveys, weather data and remote
sensing. The forecasts are highly reliable, and forecast errors decrease as the harvest time
approaches (see Figure 5.3 below). It is unclear whether the statistical crop yield forecasts
at state or county level are supported by the outputs of the crop-soil-weather simulation
models provided by local institutions and universities.
FIGURE 5.3
Reliability of US Crop Production Forecasts
Source: Holland 2011.
The US crop production forecasts are very reliable: the RMSE always remains below 0.1, and
decreases further as harvest time approaches.
2. The USA’s official national sources: methodology and
practices
2.1. Description of the general yield forecasting methodology
Crop production forecasts and estimates have two components: the number of hectares to
be harvested and the yield per hectare. A full program of forecasts and estimates includes
determinations of the areas planted at the beginning of the growing season, the estimates
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Crop Yield Forecasting: Methodological and Institutional Aspects