ARS | Publication request: Weed biomass and species composition as affected by an integrated crop-livestock system

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 9, 2009
Publication Date: August 13, 2009
Citation: Tracy, B.F., Davis, A.S. 2009. Weed Biomass and Species Composition as Affected by an Integrated Crop-Livestock System. Crop Science. 49(4):1523-1530.

Interpretive Summary: Integration of crop and livestock production, a formerly widespread practice that is rare in modern farming systems, has been shown to produce many agronomic and environmental benefits. In a field experiment near Pana, IL, we tested the hypothesis that an integrated crop-livestock system would reduce weed biomass, and shift weed community composition, compared to a continuous corn cropping system. The integrated system included two phases: 1) a corn and oat cash crop rotation. grown in summer; and 2) post-harvest grazing of corn stover with annual cover crops. Over a four year period (2004-2007), weed biomass was more than four times higher in the conventional system compared with the integrated system. Weed communities were disrupted by the integrated system, with reduced representation of summer annual weeds, usually dominant in north central field crops. Surprisingly, cattle grazing on cropland had little effect on weed biomass or species composition. Use of crop rotation and annual cover crops within the integrated system appeared to be the most important factors affecting weed management. Wider adoption of integrated crop-livestock systems, such as the one used in this study, should reduce reliance on herbicides to control weeds.

Technical Abstract: Crop and livestock production are rarely integrated together in modern farming systems. Re-integrating crops with livestock production has shown to produce many agronomic and environmental benefits. The objective of this study was to evaluate how an integrated crop-livestock system would influence weed biomass and weed species composition compared with a conventional, continuous corn cropping system. The experimental farming system used in this study was established on a 90 ha site near Pana, Illinois (USA) in 2002. The integrated system included two phases: 1) a corn and oat cash crop rotation. grown in summer; and 2) post-harvest grazing of corn stover with annual cover crops. Over a four year period (2004-2007), weed biomass was ~4.5x higher in the conventional system (8.4 g m-2 ) compared with the integrated system (1.8 g m-2). Weed species composition was affected by the integrated system and showed a temporal disjunction between the time of year and weed life history. Surprisingly, cattle grazing on cropland had little effect on weed biomass or species composition. The primary drivers that suppress weed biomass and change species composition appear to be use of crop rotation and annual cover crops within the integrated system. Wider adoption of integrated crop-livestock systems, such as the one used in this study, should reduce reliance on herbicides to control weeds.