A model was developed to assess the suitability of land in England and Wales for growing newly developed genotypes of autumn-sown determinate white lupins. The model used soil pH, the number of degree-days accumulated for mainstem leaf production before the apical meristem of the mainstem became floral, and the number of machinery work days in autumn. Interactions between these three components were used to set thresholds to determine land suitability within 5 × 5 km grid squares of the National Soil Map.
Of the potential 13·75 Mha of arable land in England and Wales, a total of 7·54 Mha are well or moderately suited to growing these lupin genotypes. This is equivalent to c. 2 Mha of land within the arable rotation each year. It was estimated that, because of low soil pH, lupins would be the preferred legume on 0·3 Mha out of this 2 Mha. The model was also used to assess the risk of soil acidification and nitrate leaching following mineralization of lupin residues. This exercise indicated that there was little risk of either on much of the land suited to lupins.