Crop rotation benefits in current sugar beet production – What can we learn from the crop rotation experiment Harste after 12 years?

The crop rotation (CR) trial at Harste was set up in 2006 to investigate the influence of varying CR (mustard (Mu)_sugar beet (SB)-winter wheat (WW)-WW, SB-WW-Mu_silage maize (SM) and Mu_SB-WW-winter oilseed rape (WOR)-WW-WW-phacelia (Ph)_grain pea (GP) on sugar beet (SB). SB yield increased in the order SB-WW-Mu_SM, Mu_SB-WW-WW and Mu_SB-WW-WOR-WW-WW-Ph_GP. However, the differences were not statistically significant in any investigation period. Main causes for high SB yield in CR Mu_SB-WW-WOR-WW-WW-Ph_GP were a high N-binding and N-supply potential as well as an improvement of soil fertility. Thus, the mineral N-fertilizer amount could be reduced and energy- and N-efficiency increased. In addition, CR SB-WW-Mu_SM was superior compared to Mu_SB-WW-WW in terms of energy- and land use efficiency as well as greenhouse gas emission. This was due to the high biomass production. However, it was not possible to ensure adequate soil organic matter supply via the crop and root residues remaining on the field in CR SB-WW-Mu_SM. For future research, there are pending issues regarding the economic viability of the entire CR and the CR impact on biodiversity.