Crop Yield Forecasting

2.6. Innovation and integration with regional/global level initiatives
The SA-GEO Agricultural Community of Practice is active in the GEOGLAM and has an active
Joint Experiment of Crop Assessment and Monitoring (JECAM) site. However, a lack of
research resources constrains the level of activity in these initiatives. The ARC, with the
CEC’s approval, contributes to the GEOGLAM bulletin each month. South African researchers
are also involved in the AgMIP crop modelling project.
3. Linking up with crop production forecast: the practices
followed by the South Africa’s official national sources
3.1. Which area data is used? Description of the methodology
The CEC uses two sources for area estimations. The first is the DAFF survey (post or e-mail).
This is used to determine the intentions to plant and to obtain a preliminary area estimate.
For the remainder of the forecasting season, it is used to underlie the PICES, which is the
second main source that must be acknowledged by the CEC. The CEC estimates the area
planted, and not the area harvested. For summer crops, the first area estimate is made in
January and may be adjusted in February and March if there is sufficient evidence to support
a revision. Otherwise, the area is rarely adjusted during a season. Most adjustments are
made in the yield estimate, in relation to the production estimate. For winter crops, the first
area estimate takes place in July and the area may be adjusted again in August.
3.1.1. The Producer Independent Crop Estimates System (PICES)
PICES is a method that was developed by NCSC and is used to estimate the areas planted
to summer and winter grain crops in South Africa. Originally, it started as a pilot project
in Gauteng in the 2004/05 summer season. PICES was developed because, although the
percentage of refusals was small with the Subjective Area Frame System, it was discovered
that there was an increasing tendency of farmers to refuse giving the necessary information.
Farmers’ refusal to participate increases the errors affecting a survey. Together with a drive
towards improved statistical accuracy and efficiency, an alternative system for area estimation
was developed that combined and integrated satellite imagery, remote sensing, point frame
statistical platforms, GIS and aerial observations from light aircraft.
PICES uses crop field boundaries that are digitized from satellite imagery with a point frame
sampling system, to objectively estimate the area planted under grain crops. The PICES
process can be summarized as follows:
• Sourcing of satellite imagery;
• Digitizing of crop field boundaries from the satellite imagery (updated annually);
• Point frame design and random selection of sample points;
• Data capturing through aerial observation of sample points; and
• Statistical analysis.
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Crop Yield Forecasting: Methodological and Institutional Aspects