Research Accomplishment Reports 2007

Weed Management Strategies for Sustainable Cropping Systems

L.J. Grabau
Department of Plant and Soil Sciences

 

Project Description

Our field work has emphasized the influence of cover crops, tillage systems, and soybean planting rates on control of grassy weeds in organically-managed corn and soybean.  Without the possibility of invoking synthetic herbicides to control grassy weeds in such crops, producers must resort to other techniques.  Grassy weeds can cause severe yield limitations, particularly in soybean production.  A key cropping system for our project has been a two-year, two-crop, two-cover crop plan.  In this cropping system, we plant winter rye in the fall, till it into the soil in the spring, and then plant soybean.  After soybean, we plant hairy vetch in the fall, then till in the hairy vetch in the spring before planting corn.  Weed control has generally been quite good for corn in this system; however, weed control has been an issue for soybean.  Higher planting rates have been helpful, especially when conditions for soybean emergence resulted in good soybean stands. 

This year, we are planning to use a laser guided cultivation system; this technology will allow us to cultivate within 7 cm of either side of each 75 cm row, and we expect to achieve much better weed control.  Further, we are also looking at a no-till organic system using a front-mounted roller to kill hairy vetch and winter rye.  The residual cover crop, left on the soil surface, and the absence of tillage is anticipated to cut down on problems with annual grassy weed species. 

We have already made two presentations on this work at the 2007 New Orleans meetings of the American Society of Agronomy, and a producer-oriented field day will be held on June 12, 2008 to discuss our findings and to demonstrate the technology and techniques we are using.

Impact

Kentucky grain producers have been somewhat reluctant to embrace organic systems.  Therefore, we believe it is our obligation to demonstrate that such systems can be successful by addressing some of the most salient problems in organic cropping systems.  That is why we have chosen to emphasize weed control in organic systems as a key research priority.  What we have learned to date is that cover crops appear to help with control of perennial weeds, but not to have a strong effect on control of annual weeds, especially grassy weeds.  Increased soybean planting rates do tend to reduce weed competition. 

We anticipate that the laser-guided cultivation system will further help in controlling weedy plants in soybean and corn crops.  The primary and direct benefit of such enhanced weed control will be improved grain crop yields.  Over time, as weed seed production declines, we anticipate that weed effective weed control will result in a continuous decline in weed pressure in organically-managed grain cropping systems.

Publications

Mroz-Barrett, M., Harris, L., Grabau, L. J., Pena-Yewtukhiw, E. M., and Grove, J.  2007.  Organic grain cropping systems and soil physical properties.  Annual Meeting Abstracts, American Society of Agronomy, New Orleans, LA.

Bruner, E., Harris, L., Grabau, L. J., Schwab, G. and Lee, C.  2007.  Cover crop influences on organic grain crop production.   Annual Meeting Abstracts, American Society of Agronomy, New Orleans, LA.