Double-crop (DC) systems are receiving serious consideration as cropping alternative for agricultural biomass production in Germany. In this study the productivity and economics of DC and sole-crop (SC) systems were compared from 2007 to 2009 at three climatically diverse sites of Germany. The warm season crops maize (Zea mays L.), forage sorghum [Sorghum bicolor (L.) Moench] and sorghum-sudangrass [S. bicolor (L.) Moench × S. sudanense (Piper) Stapf] were either grown as sole crops or as second crop following winter rye (Secale cereale L.). The winter rye first crop was harvested premature at early-to-mid May (early) or early June (late). While the winter rye was grown under rainfed conditions, maize, forage sorghum, and sorghum-sudangrass were grown with or without irrigation. Winter rye produced an aboveground dry matter yield (DMY) of 5.2 t ha–1 at early harvest and 9.0 t ha–1 at late harvest. The highest yielding DC system (rye-maize) out-yielded the most productive SC system (maize) by 3.6 t ha–1 (23%) under rainfed conditions and by 5.2 t ha–1 (24%) with irrigation. Irrigation increased DMY of sole crops by 5.3 t ha–1 (37%), of early sown second crops by 5.6 t ha–1 (43%), and of late sown second crops by 6.8 t ha–1 (77%). Under rainfed conditions, the higher DMY of the DC as compared with the SC systems did not compensate the higher production costs. With irrigation, however, the rye-maize DC achieved higher contribution margins than SC maize at two of the three experimental sites.

Journal of Cultivated Plants, Vol. 63 No. 11 (2011): Biannual issue crop science