How to use this calculator
  1. Enter January to March rainfall (mm)
  2. Enter April to October rainfall (mm)
  3. Choose the appropriate sowing window from available options
  4. Click "Calculate Yield Potential"

Grain cropping in southern Australia is entirely dependent on the occurrence and quantity of annual rain, and in most cases this is the major yield limiting factor. This calculator is based on research by French and Schultz (1984) and estimates what rainfall limited yield will be in a season. In this case, available water is the equivalent of 30% rainfall received between January and March plus 100% of rainfall during the growing season (April – October), with losses estimated at 30% of Apr-Oct rainfall. It is assumed that every millimetre of available water will produce 20kg of wheat per hectare.

A more comprehensive online production model designed to provide grain grower with real-time information about the crop during growth can be found at the Yield Prophet website.

French, R.J. and Schultz, J.E. 1984. Water use efficiency of wheat in a Mediterranean-type environment. I. The relationship between yield, water use and climate. Australian Journal of Agricultural Research 35, 743-764.