Suppressing Weeds with Rolled-Crimped Cover Crops In the Northern Great Plains.

Crop performance benefits result when conservation-tillage practices are incorporated into conventional farming systems.  Our objective was to determine if similar benefits resulted when an Organic Zero-till (OZ) system was adopted for the production of grain and seed crops.  Buckwheat, corn, and pinto bean were grown following hairy vetch, winter rye, winter wheat, and cereal-legume cover crop combinations that were killed using a roller blade in an OZ system, a tandem disk in a clean-till system, and a wide sweep in a reduced-till system during a 3-yr period in southwestern North Dakota, USA. Cereal cover crops produced more above-ground dry matter than hairy vetch cover crop (P < 0.05), and weeds were suppressed by the rolled cereal, cover crop mulch in OZ plots. However, the need to delay rolling cover crops until advanced growth stages so killing was effective resulted in late seeding of subsequent grain crops.  As a result, little if any grain was harvested in OZ plots.  These results demonstrate that weeds can be suppressed in an OZ system in the northern Great Plains, but the proportion of growing season left after cover crops are rolled prevents production of grain and seed crops.