Spatio-temporal analysis of crop rotations and crop sequence patterns in Northern Germany: potential implications on plant health and crop protection

Crop sequence patterns are considered as those schemes farmers apply within a single field to succeed crops over time, regardless of whether the same crop is grown continuously or a diverse rotation is used. This study aimed at identifying these patterns for a large and representative area in Northern Germany during a six-year period from 2005 to 2010. The analysis was carried out for the entire federal state of Niedersachsen (Lower Saxony) which has 1.8 million hectares of arable area. Field data was obtained by the Integrated Administration and Control System (IACS), which was developed for the administration of the European agricultural direct payments. So far, German IACS has not been exploited in the light of agronomical practice. In total, the available data comprised about 990 000 records for each year, each representing a single field out of the study region. Throughout the analysis, different agronomic and temporal scopes resulted in a different number of fields being accessible for evaluation. Ten major arable crops and crop groups were considered for the study; 184 701 fields representing 645 870 ha of arable area could be analyzed to identify crop sequence patterns over the six years. Thus, 16 836 combinations of the 10 major crops occurring in time and space could be described. Thereof, 12 crop sequence patterns were found covering 55.6% of arable area. For 2010, 619 447 fields representing 1 730 564 ha of arable area, were analyzed with regard to their respective crops and pre-crops. Maize, winter wheat, sugar beet, oilseed rape and potatoes were studied with special emphasis. On average, 46.9% of maize area were cropped following maize as a pre-crop. For winter wheat, self-sequences were identified on 30.0% of arable area. Oilseed rape and sugar beet are generally grown in typical rotations. However, 24.6% of arable crop area were considered as having a pre-crop which might be disadvantageous for crop health. Due to a rapid increase of maize area in the region, crop sequence patterns are undergoing a dramatic shift. It is concluded that a large proportion of arable area is potentially threatened by risks of pest and disease outbreaks as well as by economical over-reliance in a few cash crops. We demonstrate, that administrative data could offer many insights in agronomical trends and practices and should, therefore, be analyzed in more detail.