KEEPING WEEDS IN CHECK Don’t Miss the Forest for the Trees

By Whitetail Institute Staff

 It’s often said that death and taxes are the only certainties in life. We hunters and managers, though, know that there’s a third certainty: No matter how well we prepare our seedbeds, and plant and maintain our food plots, grasses and other weeds are going to show up in them at some point.
When that happens, knowing how to deal with them can be confusing if you only focus on a particular method (a tree) instead of following an integrated approach (the forest). This article will hopefully clear up some of that confusion.

To get the most out of this article, you’ll first need to have a good, general understanding of a few preliminary matters:

Preliminary Understandings What is a weed? Scientists use the term weed when describing any plant that’s growing where it’s not wanted. In this article, we’ll use the same term when describing grasses and other weeds generally. When discussing specific general types of weeds, we’ll use common references such as grass for weeds that look like grass, woody weeds for weeds like briars that have a woody, hard stem, and broadleaf weeds as a catchall for most other types.

Weed Control Methods Cultural Weed Control: Any practice that enhances crop growth and uniformity is called cultural weed control. Examples including ensuring that soil pH and nutrient levels are, and remain, optimum for the forage to be grown on the site. “Uniform crop growth is the single most powerful form of weed control in any cropping system, including food plots.” — W. Carroll Johnson, III, Ph.D

 “Physical” or “Mechanical” Weed Control: Physically removing or destroying a weed or its seeds, rhizomes or roots. Examples include repeated ground tillage before planting, and periodically mowing perennials in the spring and summer.

“Chemical” Weed Control: Herbicides. For our purposes, there are two kinds of herbicides: non-selective and selective. Non-selective herbicides don’t discriminate between forage plants and weeds. Instead, they can kill or damage any plants they enter. Non-selective herbicides include glyphosate, the active ingredient found in many Roundup brand herbicides and generic equivalents. Selective herbicides, such as the Whitetail Institute’s Arrest and Slay, kill or damage some plants without harming others when used as directed — and be sure to use them as directed. Otherwise, you can get no activity from the herbicide, or worse, kill or damage your forage plants. So remember: Before using any herbicide, consult the herbicide label. The herbicide label is the only official source of correct information there is. (A detailed article about herbicides is available at this link: ex.php?topic=753.0.)

Integrated Weed Management: An approach to weed control that incorporates cultural, physical and chemical weed-control methods to the extent appropriate for the forage.

The Forest (Goal): Healthy, Vigorously Growing Forage In his article, “Integrated Weed Management” (available on-line at the Whitetail News Archives link at www.whitetailinstitute. com), Dr. Carroll Johnson explains that physical, cultural and chemical weed control methods should be considered a three-legged stool. When it comes to things that will help keep grasses and other weeds from negatively impacting the quality of your food plots, nothing is more important than making sure your forage plants are healthy and growing vigorously. Making sure your forage plants produce as they should throughout their intended life isn’t hard. You just need to be sure you know what the steps are, and then follow them. For purposes of this article, we’ll group the steps into two categories: seedbed preparation and forage maintenance.

Seedbed Preparation Cultural Weed Control Steps: Select the correct forage for each site: Different forage-plant types grow better in certain soil and slope conditions than others. Let’s use as examples Imperial Whitetail Clover and Imperial Whitetail Extreme, two Whitetail Institute perennial forage products designed for different soil conditions. Imperial Whitetail Clover is designed for “good soil” (soils that have the ability to retain some moisture) in flatter sites. In contrast, Extreme is designed for sites that are well drained—areas with lighter soils that tend not to retain as much moisture, and that can also be more highly sloped. Because these two products are at the opposite ends of the moisture-requirements spectrum, neither might perform as well as it should if planted in a plot with the soil type and slope for which the other is designed. It’s easy to determine what Whitetail Institute forage product is right for each of your plot sites. An article explaining the process in detail is available at under the “Products” link.

Laboratory Soil Testing: If possible, have your soil tested by a qualified soil-testing laboratory. Only a qualified soil-testing laboratory can tell you exactly what your soil pH and soil nutrient levels are, and exactly what lime and fertilizer you might need to add to get the soil in optimum condition for your forage planting. If possible, try to decide what you’ll be planting so that you can note that on the soil-test submission sheet. That will allow the lab to tailor its recommendations very precisely for the particular soil type and forage. If possible, it’s also a good idea to have your soil tested at least several months in advance of planting so that you can work in any lime you need early to give it more time to work.

Addressing Soil pH if it is low: The most important factor you can control to make sure your soil is in ideal condition for your forage planting is to make sure that soil pH is neutral (between 6.5 and 7.5). When soil pH is acidic (lower than 6.5), then some of the nutrients in the soil are bound up in the soil and not available to the forage plants, and the lower soil pH is, the more nutrients are unavailable. Generally, if you plant in soil with a soil pH of 5.0, more than half of the fertilizer you put out can be wasted because the forage plants can’t get it. Having your soil tested by a qualified soil-testing laboratory is the only way to be absolutely sure you know whether you need to add lime to the seedbed, and how much and what blend of fertilizer you need to add to the soil for your seedbed to present optimum growing conditions to your forage plants. If your soil test report shows that your soil pH is acidic, don’t be surprised. Most fallow soils are acidic. If your report shows that your soil pH is acidic then it should also give you a recommendation for how much lime to add to the soil to raise soil pH to optimum levels. Add the lime as soon as you can, and disk or till it into the top few inches of the seedbed so that it can go to work as quickly as possible. This is extremely important if your forage plants are to flourish. Raising soil pH to neutral levels can also make it harder for weeds and grass to grow.

Fertilizing: Unlike lime, which should be applied a few months in advance of planting if possible, fertilize according to your soil test recommendations immediately before planting. The three numbers separated by dashes on the front of bags of blended fertilizer are (in order from left to right) nitrogen, phosphorous and potassium. Generally, nitrogen fertilizer dissipates more rapidly than phosphorous or potassium when the fertilizer is applied and exposed to the environment. Waiting to apply fertilizer until just before you plant will help you be sure your fertilizer is at full strength when the forage plants germinate and begin to grow.

Planting Depth: So far, we’ve talked about soil pH and soil nutrient levels. These are covered in the planting and maintenance instructions for each Whitetail Institute forage product, which can be found on the back of the product bags and also at www.whitetailinstute. com. Be sure that you also follow the instructions about whether to cover the seeds or not. Most Whitetail Institute food plot products are small seeds, which should be left on top of a smoothed, firm seedbed. The exceptions are Imperial Whitetail PowerPlant, Whitetail Oats Plus and Pure Attraction, which should be covered by a light layer of loose soil. If you’re not sure how to prepare your seedbed for seeding, contact the Whitetail Institute’s consultants for advice.

Physical or Mechanical Control Steps Repeated Ground Tillage (Optional): Does the soil in your food plot site contain lots of dormant weed seed? In most areas of the United States, fallow ground is heavily infested with dormant weed seed, so chances are, the answer is “yes”— and if you’ve ever tilled your soil and had weeds quickly sprout on their own, that answer is even more certain. In such cases, it can help to till the soil a few times at two-week intervals during the summer before planting. Doing so can bring dormant weed seeds to the surface, allowing them to sprout and start growing, only to be killed the next time you disk or till. A twoweek interval generally works well since any weeds that are going to sprout will usually have done so by then, and they won’t be old enough to flower and produce their own seeds within just two weeks. If you elect to incorporate this step into your seedbed preparation, try to till to the same depth each time.

Chemical Control Steps Non-selective Herbicides. (Optional): If your site is heavily infested with grass, consider performing your final tillage a month before your intended fall planting date, waiting two weeks for grass to return, spraying it with a strong glyphosate spray solution, and then planting two weeks later. If you elect to take this step, remember to not turn the soil again after you spray. It often helps to add an adjuvant such as the Whitetail Institute’s Surefire Seed Oil to the spray solution to help boost the effect of the herbicide.

Forage Maintenance Cultural Weed Control Steps: Soil pH and Soil Nutrient Levels:When soil pH has been raised to neutral by incorporating lime into the soil, it will stay in neutral range for a while. How long, though, varies because of a number of factors, including soil type, how much lime was added, and how thoroughly the lime was initially tilled into the soil, fertilizer, organic matter and even acid rain. Since soil pH is so important to forage health and vitality, it’s a great idea to perform a laboratory soil test any time you’re even considering buying lime and fertilizer. That way, you can be sure that you’re buying all the lime and fertilizer you need to keep the soil pH and nutrient levels in the plot optimum for your forage (and to be sure you don’t waste money buying lime and/or fertilizer you don’t really need).

Mowing: Periodic mowing is a step recommended for the maintenance of Imperial perennial stands. Generally, the Whitetail Institute’s maintenance instructions suggest that perennials be mowed a few times in the spring and summer, and if possible once again in early fall. Mowing in a timely manner can stimulate new growth as well as prevent the forage plants from flowering to produce seeds. The flowering process robs plants of huge amounts of nutrients and energy. Imperial perennial forages are designed to keep producing for years without reseeding, and by mowing to prevent flowering, you’ll keep nutrients and energy in the forage plants where they’ll be available to your deer. Note: Don’t mow when conditions are excessively hot and dry.

Physical or Mechanical Control Steps (More on) Mowing: Many of the weeds we face in our food plots are annual, upright weeds that rely on flowering (reseeding) to maintain their presence in our plots. Giant ragweed is an example most food plotters have experienced. In addition to the cultural weed control benefits mentioned above, periodic mowing can prevent these weeds from having the chance to reproduce. To get the full weed-control effect, though, be sure to mow these weeds before they flower. Again, mowing a couple of times in spring and summer, and again in early fall is usually sufficient. Try not to mow too much off at once — taking off only a few inches is best. If you take off more than that, then you may take off too much foliage and/or expose more of the soil to sun and wind, allowing accelerated loss of soil moisture. Also, don’t mow when your forage plants are stressed, for example when conditions are excessively hot or droughty as we mentioned above.

Hand Pulling: How often have you walked into a plot early in the season and seen just one or two weeds growing? In such cases, take the time to pull the weed, roots and all. Consider carrying a plastic bag with you anytime you’re heading to your plots. That way, you can immediately put the pulled weed into the bag and prevent any seeds it may still have on-board from dropping into your food plot.

Chemical Control Steps Unlike glyphosate, a non-selective herbicide (kills or damages any plant it enters), selective herbicides such as the Whitetail Institute’s Arrest and Slay products are tailor- made for keeping grasses and other weeds at bay in established food plots. However, not every herbicide is OK to spray on every forage. Generally, Arrest is for controlling most kinds of grass in any Imperial perennial forage and in any other clover or alfalfa, and Slay is for controlling broadleaf weeds in established stands of Imperial Whitetail Clover, and any other straight clover or alfalfa plot. To be certain Arrest, Slay or any other herbicide will control the grasses or other weeds you’re facing, and do so without harming your forage plants, the first step is to specifically identify the unwanted plants. Then, check the herbicide labels to make sure (a) that herbicide will control or suppress that specific weed or grass, and (2) that it is safe to use on the forage that’s growing in your plot. Again, the official herbicide label is the only 100 percent reliable source of information about the use, mix rates, storage, disposal, and other vital information about the herbicide. If you’re not sure whether Arrest or Slay is OK to spray on your forage, or whether it will control or suppress the weeds or grass you’re facing, call the Whitetail Institute’s inhouse consultants before you spray.

Closing Thoughts If you’ve struggled with weeds and/or grass in your food plots and haven’t known how to approach controlling them, I hope this article has given you a new vantage point. An integrated weed-control plan can keep your plots as weed-free and grass-free as possible. In most others, it will help you keep grasses and other weeds suppressed, meaning sufficiently in-check to minimize negative effects on the quality of your food plot. Either way, the practical result is the same: keeping your food plots as attractive and nutritious as possible.