Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2001
Publication Date: 5/31/2002
Citation: Reddy, K.N. 2002. Impact on rye cover crop and postemergence herbicides on weed control yieldand net return in narrow row glyphosate-resistant glufosinate-resistant andconventional soybean (glycine max). Weed Technology.
Interpretive Summary: Cover crops have several benefits, including protecting soil from erosion loss and suppressing weed growth. Declining profit margins in soybean production required assessments of the economic benefits of changing to a cover-crop-based system. A 3-year field study was conducted by the Southern Weed Science Research Unit, Stoneville, MS to determine the effects of a rye cover crop and postemergence herbicide applications on weed control and net return in narrow row transgenic and conventional soybean systems. Weed control and net return between herbicide resistant conventional soybean systems were similar. One postemergence herbicide application was more profitable than two postemergence applications regardless of soybean and cover crop systems planted in narrow rows. Rye residue reduced total weed density and biomass compared to no-cover crop systems, but additional input costs resulted in lower net returns.
Technical Abstract: A field study was conducted during 1999, 2000, and 2001 at Stoneville, MS, on a Dundee silty clay loam to determine impact of rye cover crop with one or two postemergence (POST) herbicide applications on weed control, yield, and net return in narrow row glyphosate-resistant, glufosinate-resistant, and conventional soybean systems. Cover crop systems include rye, no-cover rcrop conventional tillage (CT), and no-cover crop no-tillage (NT), all wit early POST (EPOST), EPOST followed by late POST (LPOST), and no-herbicide weed management. In glyphosate- and glufosinate-resistant soybean, one or two POST applications of glyphosate and glufosinate, respectively, were used, whereas in the conventional soybean, acifluorfen plus bentazon plus clethodim EPOST were followed by chlorimuron LPOST. Weed control and net return among glyphosate-resistant, glufosinate-resistant, and conventional soybean systems were similar. One POST ($111/ha) application of herbicides swas more profitable than two POST ($79/ha) application regardless of soybean and cover crop systems planted in narrow rows. Rye residue reduced total weed density by 9 to 27% and biomass by 19 to 38% compared to no-cover crop CT and NT. In rye cover crop, input costs were high due to additional cost of seed, planting, and desiccation. The additional cost resulted in lower net return with rye cover crop ($29/ha) compared to no-cover crop CT ($84/ha) or NT ($87/ha) system, even though rye cover crop system provided soybean yield comparable to that from the no-cover crop CT and NT system. These results showed that due to additional cost, rye cover crop-based soybean production was less profitable compared to existing no-cover crop-based production systems.