QUESTION: I'm attempting to recover a four-acre food plot that hasn't received herbicide for 30 years. I don't even plan to plant a summer crop, but am devoting all efforts to weed control. This plot is invaded by joint grass and yellow nut sedge. Will Roundup and Atrazine be adequate to kill the weeds if used in repeated doses, along with disking? If not, can SedgeHammer or similar post-emergents be used effectively? - Joseph W.
ANSWER: They say true knowledge is not knowing the answer to every question, but knowing where to find it.
Among the best sources available is Craig Harper's "A Guide to Successful Wildlife Food Plots: Blending Science with Common Sense." Appendix 3 to his book, which is adapted from the Weed Control Manual for Tennessee and includes data collected by University of Tennessee Agricultural Experiment Station and UT Extension personnel, lists the response level of weeds to various specific herbicides.
According to Harper's appendix, Dual Magnum or Eptam are among the most effective pre-plant incorporated herbicides for most grasses and for nutsedge.
Roundup, Select and Poast Plus are the most effective post-emergent herbicides for grasses.
For nutsedge, effective options include Pursuit applied as a pre-emergent or Basagran, Roundup and Atrizine as post-emergents.
Given that your weed crop is already established, and that nutsedge can be difficult to eradicate, you have your work cut out for you.
A good first step might be to disk the area prior to first plant emergence, and while doing so apply Dual Magnum or Eptam and incorporate it into the soil. This could be followed by an application of Pursuit. Though you might be better off waiting until plants emerge, then apply Roundup or Atrizine.
Don't get discouraged. It might take several applications and even several seasons to get where you want to be. Bear in mind that temperature and soil moisture and pH can affect herbicide performance; another reason why soil testing is important.
Check recommendations and follow directions for any herbicides you choose, or consult your county extension agent.