Forecasting wheat quality and the breadmaking premium from the North Atlantic Oscillation

Abstract

Those wheat varieties classified by NABIM as group 2 are dual-purpose varieties and can be managed for a feed or bread-making market. Growers currently use a wide range of intelligence in making management decisions aimed at feed or bread markets and the results of this project offer quality and premium forecasts to inform this process.

The pressure difference across the North Atlantic Ocean (The North Atlantic Oscillation or NAO) in the winter, influences the average specific weight and Hagberg falling number of the subsequent UK harvest. This report addresses the feasibility of forecasting specific weight, Hagberg falling number and breadmaking premium from the winter NAO, and presents forecasts for 3 years, 2001, 2002 and 2003.

In the development of the forecasting procedure, several published NAO indices and other climatic indices were compared. The NAO indices in the different winter months and other months of the year were also compared for their ability to forecast. It was found that the November and January NAO indices were the most useful for forecasting specific weight, and that the January and February indices were best for forecasting Hagberg. Specific weight forecasts are more reliable than those for Hagberg. The necessity for obtaining February indices early in March led to the development of a custom index from freely available gridded pressure data. The potential of forecasting with climatic indices from the preceding summer was examined but found to be of no value.

Forecasts were attempted for specific weight and Hagberg for individual regions and NABIM groups. These were of limited success and were discontinued. The effect on the forecasts of varietal mixture differences between years was tested and found unimportant.

Studies of the mechanism of the relationship have fallen into two parts. (a) The role of winter climate related to the winter NAO in determining the rate of development of the crop. (b) The direct effect of the winter NAO on summer weather, and the effect of this on the development of the crop. Only the second is of importance both for specific weight and Hagberg. The influence of the winter NAO on the climate of the following summer remains poorly understood but is being increasingly recognised.

Models for bread-making premium show that the major determinant of premium is grain quality, specific weight and Hagberg together accounting for 72% of the year-to-year differences in the premium expressed as a percentage of the feed price. Proportion of bread-making varieties grown, import price of wheat and wheat stocks are smaller additional contributors. Forecasts of premium can be made from the NAO alone, since it is a predictor of quality, and quality is the main determinant of the premium.