Experiments to evaluate the optimum plant population density and sowing date for winter peas, semi-leafless cv. Rafale, were sited on free draining sandy loam soils at Thornhaugh, Cambridgeshire in 1993/94 (Expt 1), 1994/95 (Expt 2) and 1995/96 (Expt 3). Peas were sown at the end of October, in mid-November and early December, at seed rates to achieve final plant densities in spring of 50, 70 or 90 plants/m2. Seed rates were calculated allowing for 20% seedbed loss and plant loss due to winter kill in Expt 1, and 15% in the other two years.

Peas sown in warmer seedbeds in October emerged in early December or before, November-sown peas did not emerge until mid-January and December-sown peas from late February to mid-March. The growth stage of October-sown peas was thus more advanced than the later sowings over the winter and spring period. Winters were mild for Expts 1 and 2, but there were more frost periods during Expt 3.

The yield of winter peas was dependent on sowing date. Yields of Rafale sown in October were highest in Expt 1, but lower than November-sown peas in 1995 (Expt 2), as a result of damage from late frosts during flower initiation in April, and in 1996 (Expt 3) due to plant losses after a more severe winter, frost periods and very cold winds in March. In Expts 1 and 2, yields of December-sown peas were significantly lower than November-sown peas, probably because they were adversely affected by drought stress during the sensitive flowering period. Therefore the optimum time for sowing winter pea cv. Rafale to achieve reliable yields appears to be mid-November. In some years, however, conditions may be too wet for late drilling, particularly on heavier soils.

The highest plant population densities of 90 plants/m2 gave the highest yields in Expts 2 and 3, but there was little increase between 75 and 90 plants/m2. Bearing in mind financial return and seed costs, the optimum target suggested is 75–80 plants/m2.