Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2005
Publication Date: 4/10/2006
Citation: Donald, W.W., Nelson, K. 2006. Practical changes to single-boom sprayers for zone herbicide application. Weed Technology. 20(2):502-510. Interpretive Summary: Throughout the Corn Belt, the herbicides atrazine and metolachlor persist in the soil and can contaminate surface and ground water. To minimize the chance of water contamination by herbicides, Corn Belt farmers need alternative ways to manage weeds in field crops, such as corn and sorghum (milo), that reduce herbicide use. One way to reduce total herbicide use is by zone herbicide application. Zone herbicide application does this by banding low herbicide rates between corn rows (< normal rate) and banding very low herbicide rates over crop rows (<< normal registered broadcast herbicide rate). In earlier reported research, the best zone herbicide application reduced total herbicide use to 53% of the broadcast normal rate averaged over three years. The objective of this research was to compare an older dual-boom ZHA sprayer with a newer single-boom ZHA sprayer for controlling giant foxtail and common waterhemp, major weeds, in field corn. Over two years in Missouri, these two ZHA sprayers were used to apply preemergence atrazine plus S-metolachlor, as Bicep II, between and over crop rows at different reduced rates. Based on weed ground cover and corn yield, the simpler and cheaper single-boom ZHA system was as effective as the more complicated and expensive dual-boom ZHA system. The new single-boom ZHA system is an inexpensive generic option for reducing herbicide rates, lowering input costs, and reducing the chance of surface water contamination by soil-residual preemergence herbicides. Using zone herbicide application through a single sprayer boom gives farmers a new way to reduce herbicide use and input costs while maintaining net returns. These applied results should interest farmers, extension agents, herbicide manufacturers, weed scientists, and environmentalists who wish to minimize herbicide contamination of surface water.
Technical Abstract: Reduced-rate zone herbicide application (ZHA) consists of banding reduced herbicide rates between corn rows (< full broadcast registered rate, 1X) and banding much reduced herbicide rates over crop rows (<< 1X). The objective of this research was to compare the mechanically complicated dual-boom ZHA sprayer with a much simpler, single-boom ZHA sprayer for controlling giant foxtail and common waterhemp in field corn in 2003 and 2004 in Missouri. The dual-boom ZHA sprayer employed two different herbicide solutions which were propelled through two booms on separate sprayer systems to apply different herbicide rates over in-row and between-row areas while maintaining similar carrier volumes and coverage through two booms. In contrast, the single-boom ZHA sprayer is a mechanically simpler system in which both herbicide rates and carrier volumes were varied across one boom over in-row and between-row areas. In single-boom ZHA, two different nozzle tips were alternated on one boom over in-row and between-row areas, the number of nozzles per boom was doubled, and the distance between nozzles was halved compared to a conventional sprayer boom. In a 2-yr study, these different ZHA sprayers were used to apply preemergence atrazine + S-metolachlor between and over crop rows at various reduced rates (1X = 2240 + 1750 g ai/ha, respectively). Among all single- and dual-boom ZHA sprayer treatments and the weed-free checks, corn yields and in-row total weed cover were statistically indistinguishable for both years and for between-row total weed cover in one of two yr. In both years, a single-boom ZHA system prevented yield loss from competing weeds as effectively as the dual-boom ZHA system. The new single-boom ZHA system is a mechanically simple, inexpensive, generic alternative for reducing herbicide rates and lowering input costs.