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Title: STABILITY OF CORN (ZEA MAYS) - FOXTAIL (SETARIA SPP.) INTERFERENCE RELATIONSHIPS

Author
item LINDQUIST, JOHN - UNIVERSITY OF NEBRASKA
item MORTENSEN, DAVID - UNIVERSITY OF NEBRASKA
item WESTRA, PHILIP - COLORADO STATE UNIVERSITY
item LAMBERT, W - PURDUE UNIVERSITY
item BAUMAN, THOMAS - PURDUE UNIVERSITY
item FAUSEY, JASON - MICHIGAN STATE UNIVERSITY
item KELLS, JAMES - MICHIGAN STATE UNIVERSITY
item LANGTON, STEVEN - UNIVERSITY OF WISCONSIN
item HARVEY, R - UNIVERSITY OF WISCONSIN
item Forcella, Frank

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Weed scientists around the Corn Belt are attempting to develop information about weed and crop relationships so that better weed management decisions can be made. For instance, a logical assumption is that the level of weed management in a corn crop should depend, in part, on the level of weed infestation. For this to be true, then the amount of corn grain lost because of competition from a specific density of weeds should be the same regardless of the year or location. Weed scientists from nine locations and eight states throughout the Corn Belt tested this hypothesis using the same experiment at each site. The experimental plots contained corn at normal densities and weedy grasses (giant, green, or yellow foxtail, sometimes called pigeongrass) at several different densities. Corn yield losses could then be measured and compared across sites and years using a sophisticated mathematical procedure. The results showed that maximum corn nyield losses at very high foxtail densities were relatively consistent. However, at low foxtail densities, where the decision to apply or not apply herbicides is made, corn yield losses were highly variable across sites and years. That is, there was no single general relationship that adequately predicted corn yield loss based on weed densities commonly seen in farmers' fields. This information is very useful to weed researchers, extension weed scientists, and agri-chemical industry personnel. It tells us that corn yield losses due to weeds are very site-specific, probably depending more on local weather and soil conditions during the growing season than directly on weed infestation levels.

Technical Abstract: Variation in interference relationships have been shown for a number of crop-weed associations, and may have an important impact on the implementation of decision support systems for weed management. Multi-year field experiments were conducted at eight locations to determine the stability of corn-foxtail interference relationships across years and locations. Two coefficients (I and A) of a rectangular hyperbola equation were estimated for each data set using nonlinear regression procedures. The I and A coefficients represent percent corn yield loss as foxtail density approaches zero, and maximum percent corn yield loss, respectively. The coefficient I was stable across years at two locations and varied across years at four locations. Maximum yield loss varied between years at one location. Both coefficients varied among locations. Results do not support the use of common coefficient estimates to predict crop yield loss from foxtail interference between years or among locations within a region.