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Fall applied atrazine works well on winter annual grassesBy David G. Hallauer Meadowlark District Extension agent, crops and soils/horticulture If you've ever had a weed control problem, you know that the earlier you get on it the better. That's where a product like atrazine can work really well on winter annual grasses like cheat and volunteer wheat, or winter annual broadleaves like henbit or marestail plus have a little residual left for some early spring germinating summer annuals. On marestail for instance, some programs miss it, or have developed some resistance. A tank-mix of atrazine plus 2,4-D in the fall, however, has shown enough residual to get spring germinating plants. A thorough discussion of atrazine use could fill a book, but there are a few things to consider when looking at an application. Start with the label. Atrazine is labeled in Kansas for fall application over wheat stubble or after fall row crop harvest anytime before December 31, as long as the ground isn't frozen. Corn or sorghum can be planted next spring. Understand the necessary rates. One to two pounds/acre of atrazine, usually with 1 pint/acre of 2,4-D LV4 or LV6 added, can give good burndown of the aforementioned weeds. But where one pound has done the trick for some weeds, two pounds may be needed for things like downy brome or volunteer wheat. Again, 2,4-D seems to enhance atrazine effectiveness on most all broadleaf weeds and the LVE formulation should be given strong consideration. Be aware of the proper use of atrazine containing products or tank mixes. When 2,4-D is in the mix, be aware of drift considerations, though application after fall frost have much reduced drift potential. Further, we've been granted a fall atrazine label because of our small precipitation events that tend to result in less surface water runoff. Other areas to our east aren't so lucky. We need to be cognizant of our usage so we can keep this valuable product at our disposal. To optimize foliar burn, atrazine should always be applied with either COC (when atrazine is applied alone) or with nonionic surfactant (NIS) when atrazine is tank-mixed with 2,4-D LVE. Furthermore, atrazine with NIS may be applied in nitrogen fertilizer carrier, or with paraquat (Gramoxone) herbicide, both of which further enhance foliar burn. Fall tree planting We usually think of planting trees in the spring rather than now, but fall may have advantages. During the spring, soils are cold and may be so wet that low oxygen levels inhibit root growth. The warm and moist soils associated with fall encourage root growth that helps trees better stand summer stresses. Certain trees do not produce significant root growth during the fall months and are better planted in the spring (birch, redbud, magnolia, tulip poplar, willow oak, scarlet oak, black oak, willows and dogwood). Fall-planted trees require some special care. Roots are actively growing even though the top is dormant so make sure the soil stays moist (not soggy). This may require watering not only in the fall but also during the winter months if we experience warm spells that dry the soil. Mulch also is helpful because it minimizes moisture loss and slows the freezing of the soil so root growth continues as long as possible. Evergreens should be moved earlier in the fall than deciduous plants as they need at least six weeks before the ground freezes for root establishment. 10/13/08 Date: 10/10/08
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