August 14, 2020
Fallow can be a rotational tool used in the western Great Plains for dryland fields. No-till fallow can improve water infiltration, reduce evaporation, and increase the amount of moisture in the soil at planting. However, failure to control weeds in a fallow period can reduce soil moisture and contribute weed seeds to the field seed bank.
Volunteer corn is a common weed found in fallow acres that should be controlled in order to realize the full potential of benefits. Weeds use large amounts of water, which defeats the purpose in a fallow situation. According to a study done by Kansas State University, for every 2,500 plants per acre of volunteer corn, available water was reduced by 1 inch.1 By no surprise, the impact of volunteer corn will be higher if followed by a time period of low precipitation.
The amount of volunteer corn will be higher if preceded by late season lodging along with significant kernel losses at harvest. Late season lodging in corn can be caused by a multitude of factors including stalk rot diseases, nitrogen deficiency, insect infestations, or hail damage. To minimize harvest losses, aim to harvest grain at the appropriate moisture content and adjust harvest equipment to minimize losses. The use of no-till can limit the germination potential of volunteer corn versus conventional till.
Producers have options to control volunteer corn. Grass herbicides, clethodim for example, can be applied to control glyphosate-tolerant volunteer corn. A post-emergence only option would be paraquat herbicide. To provide both pre-emerge and post-emerge control of volunteer corn, consider tank mixing atrazine and paraquat. This tank mix combination controls a wide span of weeds in addition to just volunteer corn. To have the most success, weeds should be controlled when small (4 inches in height or less). Be sure to check labels for specific size recommendations on weed height. Additional control methods include tillage and grazing.
To have a successful fallow period, aim to maintain as much residue on the soil surface as possible. This helps aid infiltration, while limiting evaporation losses. Greater residue may also limit weed germination rates. An effective fallow period can mean higher yield potential for your next crop.
Sources:
1Holman, J., Dumler, T., Maxwell, S., Olson, B., Roberts, T., Schlegel, A., and Thompson, C. 2011. Keeping up with research: Volunteer corn in fallow. SRL 141. Kansas State University Agricultural Experiment Station and Cooperative Extension Service.
Klein, R. 2012. Managing corn and grain sorghum residues during the pre-winter wheat fallow period. NebGuide. G1648. Nebraska Extension. University of Nebraska. http://extensionpublications.unl.edu/.
Websites verified 5/7/2020
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