Dual Boom Versus Single Boom Zone Herbicide Application (ZHA) In Field Corn

What is Reduced Rate-Zone Herbicide Application (ZHA)? Reduced-rate ZHA uses: 1) crop management to enhance crop competitiveness with weeds, 2) soil residual herbicide banded over crop rows at reduced rates (Figure 1) and 3) the same herbicide banded between rows at higher rates than in rows, but less than the maximum registered rate. The net result is that ZHA reduces total herbicide use per acre and herbicide input costs for farmers.

What Can Reduced Rate-Zone Herbicide Application Do for Farmers?
Economics:

• ZHA reduces total preemergence, soil residual herbicide use and herbicide input costs in competitive field crops without compromising net returns. For example in Missouri research, atrazine + s-metolachlor (e.g., Bicep II herbicide) use in field corn was reduced up to 47%, without reducing net returns.
• ZHA is best done at planting with special sprayer booms mounted on planter boxes. Cost savings on herbicides with ZHA quickly pay for spray boom construction. Spray boom construction is cheap, and sprayer parts are commercially available. ZHA sprayer calibration is simple.
• Reduced rate-ZHA of soil residual herbicides makes them be no more costly to farmers than herbicide-resistant GMO crops technology, without technology fees or restrictions on replanting saved seed.

• ZHA is an additional, alternative way to manage weeds which keeps decision making for weed management in the farmer’s control, not commercial custom applicator.
• ZHA can be used on land with terraces, grassed waterways, or center pivot irrigation
• ZHA is a generic herbicide application method and can be used with many preemergence, soil residual herbicides in many row crops. It isn’t limited only to atrazine + smetolachlor (Bicep II) in corn.
• ZHA does not require major or expensive change to current weed management and crop production practices.
• Reduced-rate ZHA may slow selection and evolution of herbicide-resistant weeds.
• ZHA reduces the chance of herbicide damage to crops.

• By reducing herbicide use, ZHA helps reduce herbicide movement in runoff from fields and minimizes the chance of surface and ground water contamination by herbicides.
• By reducing water contamination by herbicides, public drinking water suppliers don’t have the added cost of herbicide cleanup to comply with E.P.A. drinking water standards.

• By reducing reports of atrazine (Aatrex 4 L and numerous commercial herbicide mixtures containing atrazine) and other herbicides in drinking water, ZHA will reduce public fear of drinking water contamination by herbicides.
• In turn, this may help prevent these herbicides from being banned by government regulatory agencies. Thus, ZHA may help keep some herbicides on the market and available to farmers for weed management.

Even flat spray nozzle tips (all the same) (e.g., Tee Jet TP 4001 E)
	Band application Premergence herbicide is banded over the crop row followed by field cultivation between rows later	This older herbicide spray system was used for banding preemergence herbicides in the 1950’s and 1960’s.
Standard flat spray tip (all the same) (e.g. Tee Jet TP 8002)
	Broadcast application Preemergence herbicide is broadcast both over and between crop rows	This conventional broadcast herbicide spraying system is used now.
In Zone Herbicide Application (ZHA) different herbicide rates are applied between rows (BR) and in row (IR) using even nozzle tips and one spray boom so that the total amount applied is reduced up to 50% compared to broadcast treatments.
Different even flat spray nozzle tips with different output alternate in row and between row (e.g., Tee Jet TP 4001 E in row and TP 4003 E between row)
	Zone herbicide application (ZHA) with premergence herbicide rates between rows greater than in rows so that less total herbicide is applied less than broadcast treatments	This new adaptation of older banding methods has potential to reduce herbicide inputs preemergence treatments up to about 50% without reducing $ returns
	Zone herbicide application of preemergence herbicide is best made at planting. Spray nozzles can be attached to planter boxes so that herbicide is applied at different rates in row and between row. This approach means that zone herbicide application can be made on farmland with terraces.
Herbicide is non-uniformly applied relative to the crop row, so that less is applied (up to 50% less) than when broadcast.

The characteristics of zone herbicide application with either dual booms or a single boom are compared with standard flat fan broadcast herbicide application in Table 1. The rate of herbicide application with broadcast or dual boom ZHA is determined by herbicide concentration in the spray tank after calibration, and other factors (e.g. carrier volume, speed, etc.) are held constant. Calibration procedures are the same for either broadcast application or dual boom ZHA systems. Coverage should be similar with either application method because they both use one type of nozzle, although there may be a greater chance for coverage problems with improper ZHA (Table 1). In contrast to dual boom ZHA, the herbicide rate for single boom ZHA is regulated by both (a) herbicide concentration and (b) carrier volume of application with different nozzles. Carrier volumes in-row (IR) are less than between row (BR) for single boom ZHA, so coverage will vary in these two row positions. This should not reduce weed control efficacy with PRE soil-residual herbicides. POST translocated herbicides should perform better than POST contract herbicides with single boom ZHA (e.g., glyphosate versus glufosinate) (i.e., less dependence on spray carrier volume and coverage for good efficacy), but this remains to be researched.

Research objectives:
The objectives of this research are to (1) determine whether dual boom and single boom ZHA systems perform alike with PRE soil residual herbicides (e.g., atrazine / metolachlor in corn).
(2) verify that the single boom ZHA has the same advantages over broadcast application as the dual boom ZHA.

Results:
This experiment is a repeat of one conducted at Greenley in 2003. Results for the two trials are comparable and successfully establish the objectives of the study.

Table 1. Comparison of reduced rate broadcast versus dual and single boom zone herbicide application.