ABSTRACT
This study provides current data on plant nitrogen (N) uptake required for maximum sugar yield (PNUpmax) and the corresponding fertilizer N dose (ND) (optimum N dose [NDopt]) for high-yielding beet crops (sugar yield up to 20 Mg ha−1). In 2010 and 2011, field experiments were conducted with four cultivars from Beta genus differing in dry matter composition, and six mineral NDs (0–200 kg N ha−1) at three sites (The Netherlands, Germany, Denmark). Differences between cultivars in PNUpmax and NDopt were small; however, environments (defined as combination of site and year) substantially differed from each other: highest PNUpmax 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 PNUpmax (200–270 kg N ha−1) nor to NDopt. However, N dose and plant N uptake required for 95% of maximum sugar yield was 50–80 kg N ha−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.
Acknowledgements
We gratefully acknowledge the excellent technical work of the staff of our institutes IRS, IfZ and NBR in the field and lab. ‘Thank you’ to Dr. Christian Kluth for calculating the inverse polynomial functions. This work was conducted as a COBRI project (Coordination Beet Research International).
Disclosure statement
No potential conflict of interest was reported by the authors.