Nitrogen requirement of fodder and sugar beet (Beta vulgaris L.) cultivars under high-yielding conditions of northwestern Europe

This study provides current data on plant nitrogen (N) uptake required for maximum sugar yield (PNUp(max)) and the corresponding fertilizer N dose (ND) (optimum N dose [NDopt]) for high-yielding beet crops (sugar yield up to 20Mgha(-1)). In 2010 and 2011, field experiments were conducted with four cultivars from Beta genus differing in dry matter composition, and six mineral NDs (0-200kgNha(-1)) at three sites (The Netherlands, Germany, Denmark). Differences between cultivars in PNUp(max) and NDopt were small; however, environments (defined as combination of site and year) substantially differed from each other: highest PNUp(max) and lowest NDopt occurred at environments supplying high amounts of N from soil resources, and vice versa. The level of maximum sugar yield (SYmax) was related neither to PNUp(max) (200-270kgNha(-1)) nor to NDopt. However, N dose and plant N uptake required for 95% of maximum sugar yield was 50-80kgNha(-1) lower than for maximum sugar yield. To conclude, accepting a slight reduction in sugar yield might allow for a substantial decrease in the ND. Cultivar choice and yield level need not to be taken into account at present.