Cereal and oilseed rape harvest: Methodology

Final estimates methodology

Final estimates of production and usage are based mainly on final yield results from the Cereal Production and Disposal Survey (CPDS) and final crop areas from the June Agricultural Census. The survey asks farmers to provide figures for each crop on each holding and is carried out online, by mail and by telephone.

In some years a different methodology has been used to create estimates. Final estimates in 2022 and 2020 use a different methodology. First estimates are not available for 2022. More information about these changes is available under Changes to methodology.

The CPDS is a disproportionate stratified random sample of around 500 farms in Scotland, stratified by region. In 2023 the sample size was increased to around 1,200 farms. Oversampling in some groups is designed to ensure that the result has good representation of all groups.

To provide reliable estimates of the year-on-year changes in production, the CPDS is carried out at the same time each year. The reference date for the CPDS, the date at which respondents are asked for production information, is the 31st October each year.

Totals of sample production and sample crop area for each stratum (i.e. crop and region combination) are used to derive a sample estimate of yield. These yield values are applied to national crop areas from the June Agricultural Census to calculate national estimates of production.

Where sample sizes for strata are insufficient to calculate production results national average yield estimates for the crop are used to calculate estimates of production. Regional results for winter oats and spring oilseed rape are often based on national averages.

As the moisture content of cereals and oilseed rape can vary from year-to-year and farm-to-farm, depending on the level of rainfall, average yields are adjusted to a standard moisture content of 14.5% for cereals and 9.0% for oilseed rape. This adjustment ensures there is consistency in estimates of the amount of dry matter which can be extracted from cereal grain and oilseeds.

The survey collects cereal usage or disposal estimates of barley, wheat and oats. Farmers who have taken part in the CPDS are asked how much of their crops have been used and where their crops have been used.

First disposals from the harvest year are collected in November along with estimates of production from the harvest year. As crops may continue to be sold well into the following year, further disposals data are collected from farms that have not completed their disposals in the following year.

Production figures are published as soon as they have been confirmed, usually in December of the harvest year. Disposal figures, which continue to be collected into the following year, are published with the following year’s first estimates of production.

Disposals data published by the Scottish Government only relates to disposals from the associated harvest year and does not contain information about disposals of crops that have been carried over from previous years.