Weed Control and Crop Injury with Single or Sequential Herbicide Applications in Grain Sorghum

Kansas Agricultural Experiment Station Research Reports, Aug 2016

The preemergence application of Dual II Magnum (S-metolachlor) improved the overĀ­all weed control compared to single postemergence treatments. Excessive rainfall after preemergence application compromised all treatments, producing abnormally low weed control.

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Weed Control and Crop Injury with Single or Sequential Herbicide Applications in Grain Sorghum

Weed Control and Crop Injur y with Single or Sequential Herbicide Applications in Grain Sorghum R . Currie 0 1 Kansas State University 0 1 0 1 P. Geier 0 1 0 Kansas State University , USA 1 Kansas State University Agricultural Experiment Station and Cooperative Extension Service , USA Follow this and additional works at: http://newprairiepress.org/kaesrr Part of the Agronomy and Crop Sciences Commons, and the Weed Science Commons Recommended Citation Currie, R. and Geier, P. (2016) "Weed Control and Crop Injury with Single or Sequential Herbicide Applications in Grain Sorghum," Kansas Agricultural Experiment Station Research Reports: Vol. 2: Iss. 7. https://doi.org/10.4148/2378-5977.1271 - Thi s report is brought to you for free and open access by New Prairie Press. It has been accepted for inclusion in Kansas Agricultural Experiment Station Research Reports by an authorized administrator of New Prairie Press. Copyright January 2016 Kansas State University Agricultural Experiment Station and Cooperative Extension Service. Contents of this publication may be freely reproduced for educational purposes. All other rights reserved. Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. K-State Research and Extension is an equal opportunity provider and employer. Weed Control and Crop Injury with Single or Sequential Herbicide Applications in Grain Sorghum Creative Commons License Thi s work is licensed under a Creative Commons Attribution 4.0 License. Thi s Weed Science article is available in Kansas Agricultural Experiment Station Research Reports: http://newprairiepress.org/ kaesrr/vol2/iss7/26 Agricultural Research Weed Control and Crop Injury with Single or Sequential Herbicide Applications in Grain Sorghum R. Currie and P. Geier Summary The preemergence application of Dual II Magnum (S-metolachlor) improved the overall weed control compared to single postemergence treatments. Excessive rainfall after preemergence application compromised all treatments, producing abnormally low weed control. Introduction When conducting a weed control experiment focused primarily on broadleaf weed control, excessive grassy weed pressure will often compromise results. If one applies a full rate of any of several preemergence grass control compounds, they can often but not always produce a level of broadleaf weed control that defeats the original purpose of the experiment. Therefore, it was the objective of this experiment to compare a set of postemergence broadleaf weed control compounds with and without a preemergence application of a half rate of the grass control compound Dual II Magnum. Procedures An experiment at the Kansas State University Southwest Research-Extension Center near Garden City, KS, evaluated the crop response and efficacy of Huskie (pyrasulfotole + bromoxynil) tank mixtures in grain sorghum. Huskie treatments were applied either as stand-alone postemergence treatments or as sequential treatments following a preemergence application of Dual II Magnum. Preemergence applications were made June 10, 2015 and postemergence applications were made July 6, 2015, when sorghum was 6 to 10 inches tall and weeds were 2 to 7 inches in height. All treatments were applied using a tractor-mounted, compressed CO2 sprayer delivering 20 gpa at 3 mph and 30 psi. Soil was a Ulysses silt loam with 1.4% organic matter, pH of 8.0, and cation exchange capacity of 18.4. Plot size was 10 by 35 feet, and plots were arranged in a complete randomized block with four replications. Visual sorghum injury was taken on July 13 and July 30, 2015, 7 and 24 days after postemergence application (DAPT). Weed control was estimated visually on September 15, 2015, which was 71 DAPT. Grain yields were not determined. Results and discussion All Huskie treatments caused 5 to 10% sorghum necrosis at 7 DAPT (Table 2), but sorghum had completely recovered by 24 DAPT. Palmer amaranth control at 71 DAPT was greatest (78 to 81%) when Dual II Magnum preemergence was followed by Huskie at 13 oz/a, atrazine, Banvel (dicamba), NIS and AMS or with Huskie at 16 oz/a plus atrazine and NIS. Dual II Magnum applied preemergence increased Palmer amaranth control with Huskie at 13 oz/a plus atrazine and 2,4-D or Banvel or Huskie at 16 oz/a plus atrazine postemergence compared to the same treatments applied alone postemergence. Dual II Magnum alone preemergence controlled green foxtail 68%. When Dual II Magnum was applied preemergence and followed by any Huskie postemergence treatment, green foxtail control increased 34 to 65% compared to the postemergence-only Huskie treatments. Although it did improve broadleaf weed control, the application of a half rate of Dual II Magnum did not provide a level of control so high as to compromise the experiment. Results were dramatically influenced by excessive rainfall and subsequent irrigation after application. Many previous studies with these compounds have produced much higher levels of control. It is common for growers to apply a set of early preemergence treatments three months prior to planting, followed by postemergence applications. The use of very early preemergence treatments was not used because resulting control with preemergence and postemergence treatments often produces 100% control, defeating the purpose of the experiment. In hindsight, had this been done, it would have reduced the impact of excessive rainfall and produced more normal levels of weed control. 7 DAPTa 71 DAPT Sorghum Palmer Green necrosis amaranth foxtail ---------------------- % visual ---------------------0 50 68 6 43 72 Treatmentb a DAPT is days after postemergence application. b NIS is nonionic surfactant and AMS is ammonium sulfate. c PRE is preemergence, POST is postemergence. Kansas State University Agricultural Experiment Station and Cooperative Extension Service


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R. Currie, P. Geier. Weed Control and Crop Injury with Single or Sequential Herbicide Applications in Grain Sorghum, Kansas Agricultural Experiment Station Research Reports, 2016,