Influence of sowing and harvest dates on production of two different cultivars of sugar beet

Small-plot trials conducted in 2013-2015 studied the impact of longer vegetation periods (by means of earlier drilling and/or later harvest) on production results of two sugar beet cultivars -one nematode-tolerant cultivar and one cultivar without such tolerance. The trials took place at two sites with different Heterodera schachtii infestation levels. In all trial seasons, root yield was significantly higher in the earlier drilled plots. On average, prolongation of the vegetation period in spring by 13 days increased root yield by 10.9%. Therefore, each day by which drilling is postponed represents a 0.7-0.8% loss of yield. As to sugar content, no statistically significant benefit of vegetation period prolongation by early drilling was found. The spring gain was slightly higher for the non-tolerant cultivar than for the tolerant one on average over all trial seasons. This result confirms the theory that nematodes impact the crop mainly in later stages of vegetation, and early drilling can thus help eliminating, to a certain degree, the risk of nematode damage. In the autumn, root yield increased by 14.3% on average over 39 days. The autumn daily gain was about half of the rate found in the spring. The increase in sugar content was between 0.6% and 1% (abs.) on average. Autumn growth achieved at the non-infested site was much higher than at the infested site.