Yield potential of non-bolting winter sugar beet in Germany

Abstract Autumn-sown, non-bolting winter beets may show a faster canopy formation in spring. In order to estimate their yield potential, a dynamic model for winter beet was used to compare growth and yield of conventional, spring sown sugar beet (CB) with two non-bolting winter beet types at five representative sites across Germany. Non-bolting winter beets (WB) were parameterized according to available experimental data and hypothetical, whereas more frost-sensitive, non-bolting winter beets (WBfs) were assumed to show higher frost-induced leaf losses during winter. The simulation results (harvest years 1998–2010) revealed an earlier leaf area formation for both winter beet types compared to CB, resulting in an average potential yield benefit of 27 % for WB and 23 % for WBfs. However, at 2 out of 5 sites, frost completely killed the winter beets in at least one year. Simulated evapotranspiration of both winter beet types clearly exceeded that of CB. Winter beets showed an increased water use efficiency (WB: 3.8 g l−1; WBfs: 3.7 g l−1) compared to spring sown CB (3.4 g l−1), whereas the transpiration use efficiency was similar for all beet types. For the growth period of April till October, the ratio of potential to actual transpiration indicated a higher drought stress for the winter beet types. Our results reveal that growing non-bolting winter beets may enhance potential beet yields, but the increasing water demand and the risk of frost-killing have to be taken into account.