Reduced Herbicide Use Through Improved Mechanical Cultivation and Banding of Herbicides

Reduced Herbicide Use Through Improved Mechanical Cultivation and Banding of Herbicides

Summary

Objectives

The overall goal of this project was to provide cotton growers in the southwestern United States with effective, commercially acceptable alternatives to extensive herbicide use for weed control.

1. Evaluate and demonstrate cultivator guidance technologies under Arizona field conditions.
2. Evaluate and demonstrate the potential for revitalizing old in-row and close-to-the-row cultivation technologies that were abandoned when herbicides were introduced.
3. Evaluate and demonstrate guidance systems in combination with herbicide banding.
4. Develop and evaluate at least one new cultivation system.
5. Compile operational and cost data on reduced herbicide vs. conventional weed control systems.
6. Disseminate information relative to the advantages of alternative weed control systems.

Abstract

Field trials showed that mounting the sensing wand on the second row, rather than on the first or outside row, increased a guidance system’s ability to follow a simulated row of cotton plants. A slide guidance system provided better accuracy than either of the two articulated systems tested, in that it kept the cultivator more closely aligned to the row as the tractor deviated from a path parallel to the row. A mechanical digger, designed to lift nutsedge tubers from depths of up to six inches to the soil surface where the sun could dessicate and kill them, proved functionally acceptable. Unfortunately tubers deeper than six inches were able to send shoots to the soil surface. Tilling deeper than six inches is considered energy inefficient, and hence this technique holds little commercial promise. A mechanical weeding system that utilized two heavy-duty weed eaters, one placed on either side of the row, showed promise in cotton. Additional work to develop the system is required, however. A precision-guided cultivator, equipped with beet hoes set to cultivate within two inches of both sides of the row, required three times the energy of a conventional system equipped with rolling cultivators spaced four inches from each side of the row. The increased energy requirements were not considered to be sufficiently negative to preclude the use of such systems, since the increased weed control and decreased field time possible with the precision system would more than compensate for the increased energy requirement.

Several large-scale research and demonstration field plots that combined the use of recently developed selective broadleaf herbicides (Buctril, Roundup, and Staple) and transgenic cotton varieties (BXN and Roundup Ready) with precision-guided cultivation were established in fields with annual morning glory.

The successful combination of herbicide and precision cultivator technologies to eliminate weeds was demonstrated in field days to cotton growers in all cotton-producing counties in Arizona (Graham, La Paz, Maricopa, Mohave, Pima, Pinal, and Yuma counties). In addition to direct information transfer to growers, the demonstrations and field days also led to popular magazine articles, several radio station interviews, and a TV station interview. Research was conducted on University of Arizona (UA) Experiment Stations, with the results published in the UA’s College of Agriculture Cotton Report. The trials showed that costs could be reduced by banding (10- to 15-inch bands on 40-inch beds) early season post-emergence herbicide sprays in both dry plant and plant to moisture (i.e., wet plant) cotton production systems without reducing weed control or cotton yield, when done in conjunction with precision cultivation. In dry plant systems preplant incorporated herbicides such as Prowl or Treflan could be incorporated in a band (18- to 20-inch bands on 40-inch beds) on the bed top prior to planting, without sacrificing weed control or yield.

The information, results, and experience obtained during the course of the project were integrated into several Cooperative Extension Bulletins and will aid in the preparation of additional research reports, Extension Bulletins, and the development of a cotton Web site at the UA. As a result of the information transfer, a number of articulated, precision guidance systems were purchased by farmers in Arizona for use with cultivators and other implements. Thus, precision cultivation technology has been successfully demonstrated in Arizona and has been adopted by a number of cotton farmers.

Potential Benefits

Adoption of mechanical weed control methodologies will have several benefits:

1. Reduction of hand weeding costs for annual morning glory and other broadleaf weeds from $50 to $100 per acre to zero.
2. Reduction in weed competition resulting in increased yield.
3. Reduction in chemical use through the elimination of preplant incorporated broadleaf herbicides such as prometryn for a reduction in chemical use of 1.2 to 1.6 pound of active ingredient (a.i.) per acre and a cost reduction of about $9.50 to $12.67 per acre.
4. Increase in farm profits as a 150 percent increase in cultivation speed and a corresponding savings of fuel, labor, and future capital costs, associated with needing fewer tractors to farm the same number of acres, can be realized.

Farmer Adoption

Articulated guidance systems, close cultivation, and in-row weeding technologies have been adopted as has the use of banded applications of post-emergence herbicides rather than broadcast applications of pre-emergence herbicides. Prior to 1996, there were virtually no Acura Trak hitches in use in Arizona. Since the project began, a number of articulated guidance systems for use with cultivators and other farm implements have been purchased. Currently approximately 50 Acura Trak hitches are in use on cultivators in Arizona, with another 20 used for other applications. In Yuma County, there are now more listers used with Acura Trak hitches than without. The use of Staple herbicide on conventional cotton varieties and Roundup Ultra on Roundup Ready cotton varieties is now widespread in the state, with a concomitant reduction in the use of preplant broadleaf herbicides.

Operational Recommendations: 1) placing band applications of dinituroaniline herbicides (Treflan and Prowl) on the bed top prior to planting, rather than broadcast applications in dry plant production systems. 2) Eliminate the use of broadleaf preplant herbicides in both wet and dry plant production systems. 3) Use early season over-the-top and post-directed herbicides to control weeds and establish a height and size differential between cotton and weeds. 4) Use precision guidance systems in combination with close cultivation and in-row weeding techniques to maintain fields weed free until layby. 5) Assess weed population pressures and apply postemergence and layby herbicides on an as needed basis.

Reactions from Farmers and Ranchers

Reaction from growers to the project and the concepts presented has been positive. A number of growers have purchased guidance systems as well as cultivators that permit close to the row and in row cultivation. The use of precision cultivators in combination with new herbicide technologies has become relatively common. Thus, it is considered that the project has been very successful. Use of new over-the-top herbicides and precision cultivation technologies does require more management skills, and the precision guidance systems require more proficient tractor drivers and supervisors to properly operate and maintain the equipment. In a few cases, this has been an impediment to continued use of precision cultivation.

Future Recommendations

Additional reductions in herbicide use can be achieved by using precision guidance systems for early season band applications of Buctril, Roundup Ultra and Staple herbicides. Standard band applications are usually about 15 inches wide. With close cultivation and accurate spray placement, this width can be reduced to about eight to ten inches, reducing herbicide use substantially.

Before cotton plants are large enough to be detected by the sensing wands, reference furrows, and furrow tracking devices must be used to guide the cultivator and permit mechanical eradication of weeds. The use of precision cultivation and application of narrow bands of herbicide could be improved by optically sensing the crop row, rather than mechanically sensing the furrow or crop rows.

This summary was prepared by the project coordinator for the 2000 reporting cycle.

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