Crop Yield Forecasting

take place, and the maximum daily temperature, beyond which phenological activity no
longer increases.
The output variables are the following:
• Crop development stage;
• Crop total biomass and yield under potential & water-limited conditions;
• Crop LAI under potential & water-limited conditions; and
• Soil moisture and transpiration.
In recent years, the FROST variable was added to take into account the risk of frost for
winter crops (wheat and barley). The FROST variable is calculated by weather variables and
represents the number of frost days between 1 December and 31 March of a given year. A
day is considered to have frost when the minimum temperature is below 0°C.
2.2.9. Crop yield forecast
The WOFOST model provides the following indicators, at 10-day (dekad) intervals:
• Biomass and yield of storage organs in potential conditions and under real
precipitations;
• Estimated soil water reserve (the difference between current and past dekad or
past month);
• Development state of crop cycle during the current dekad.
The final crop yield forecast (Y) is obtained by combining the outputs of the function on
technological trends with those of the agrometeorological model and of the biomass
indicator, as given by remotely sensed data. The model’s equation is:
Y = a + f 1 (Trend) + f 2 (CGMS) + f 3 (RS) + ξ
where
Y
f 1 (t)
f 2 (CGMS)
f 3 (RS)
ξ
= the forecasted yield
= the function linked to the technological trend
= the function linked to the meteorological conditions (agrometeorological
model)
= the function linked to the biomass indicator as given by remotely sensed
data
= the random component (error).
For each circumscription or agricultural region, a linear 42 or quadratic 43 function of the
technological trend is calculated or adjusted by the least square method, over periods of 15
and 30 years.
42
Linear function: y = a + b 1 t.
43
Quadratic function: y = a + b 1 t + b 2 t².
40
Crop Yield Forecasting: Methodological and Institutional Aspects