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Texas Agricultural Experiment Station and Texas Cooperative Extension
Principal Investigator: Peter Dotray, Texas A&M University Agricultural Research and Extension Center, Route 3, Box 219, Lubbock, TX 79403-9757. E-mail: p-dotray@tamu.edu
Cooperators: Mike Schubert, Wayne Keeling, Eduardo Segarra, and Alan Brashears
Graduate Research Assistant: Alan Peters
Primary Research Location: Texas Tech Research Farm near New Deal and the Western Peanut Growers Farm near Denver City. Satellite studies were conducted at Ropesville, at AG-CARES near Lamesa, and at the Texas Agricultural Research and Extension Center in Lubbock.
Project Title: Weed Mapping and the Economic Benefit of a Light-Activated Weed Sprayer in Texas Southern High Plains Peanut and Cotton Production
Project Objectives: 1) Compare conventional weed control systems to one using a light-activated hooded sprayer; 2) determine the economic benefit of using a light-activated hooded sprayer; and 3) map the presence of weeds in a field and relate to yield and long-term weed control over time.
Reporting Period: January 1, 2000 to December 31, 2001
Field experiments were conducted in 2000 and 2001 near New Deal, TX to compare weed control in a glyphosate-tolerant cotton production system using mechanical cultivation, a conventional hooded sprayer, and a light-activated hooded sprayer. Treatments included trifluralin at 0.75 lb/A applied preplant incorporated (PPI) followed by prometryn at 1.2 lb/A applied preemergence and mechanical cultivation as needed; trifluralin PPI followed by a postemergence topical (PT) broadcast application of glyphosate at 1 lb/A at the four leaf growth stage, and glyphosate applied at 1 lb/A with a conventional hooded sprayer (HS) as needed; trifluralin PPI followed by glyphosate PT broadcast and glyphosate applied at 1 lb/A with a light-activated hooded sprayer (LAS) as needed; and trifluralin PPI followed by a PT application of glyphosate at 1 lb/A on a fourteen inch band over the row at the four leaf stage and glyphosate applied at 1 lb/A with LAS as needed. ‘Paymaster 2326 RR’ cotton was planted at a seeding rate of 15 lb/A on 40 inch rows on May 9, 2000 and May 10, 2001 and harvested November 20, 2000 and December 10, 2001. Experimental design was a randomized complete block consisting of four replications. Plots were 8 rows by 600 feet. Preplant incorporated treatments were applied February 29, 2000 and March 2, 2001, and incorporated with a springtooth harrow. Preemergence applications were made on May 10 both years. Postemergence treatments were applied on June 9, July 3, and July 18 in 2000 and June 9 and July 5 in 2001. Weeds were 1 to 6 inches in height at the time of application. Control of Palmer amaranth (Amaranthus palmeri S. Wats), common cocklebur (Xanthium strumarium L.), and silverleaf nightshade (Solanum elaeagnifolium Cav.) was visually rated on June 17 (early season), July 28 (mid season), and August 14 (late season) in 2000 and June 23, July 19, and August 2 in 2001. The amount of spray solution used by the LAS was determined by subtracting the volume remaining after spraying a single plot from the initial volume in the tank. Percent herbicide savings was calculated based on the amount of solution required to apply a broadcast treatment.
In 2000, control of Palmer amaranth ranged from 83-88% for all treatments at the early rating (see graphs below). At the mid and late season ratings, the LAS treatments provided at least 88% control and were similar to HS and greater than cultivation. Common cocklebur control with LAS was similar to HS and greater than cultivation at all rating dates. Silverleaf nightshade was controlled 31-40% by all treatments at the early rating. At the mid and late season ratings, LAS provided control similar to HS and greater than cultivation.
In 2001, Palmer amaranth and common cocklebur control at all rating dates was similar to HS and ranged from 75-93% for both weeds when LAS was used following a PT broadcast application of Roundup Ultra (see graphs below). However, when LAS was used following a band application, Palmer amaranth control at the mid and late season ratings was reduced when compared with LAS following a broadcast application. At the early and late season ratings, silverleaf nightshade control with LAS was similar to HS, but mid season control was greater for HS (80% vs 68%).
Herbicide savings in 2000 were 85% for the June application, 63 and 67% for the July 3 application, and 56 and 71% on July 18. In 2001, observed herbicide savings were 73% for the June application and 84 and 62% for the July application (see graphs below).
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Lint yields ranged from 380 to 430 lb/A in 2000 and 500 to 940 lb/A in 2001. No differences in yield were observed from the glyphosate treatments (HS vs. LAS) in either year (see graphs below).
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In summary, weed control by the LAS was more effective in 2000 than 2001. We look forward to our final year of yield testing in 2002 to better predict the utility of using a LAS in west Texas.
In addition, fields were weed mapped in 2001 to determine whether weeds were randomly distributed over the field and to observe population changes over time. As previously stated, no significant yield differences were observed, so no correlation could be made between weed population and yield reduction. Field maps, however, will still provide a snap shot of weed distribution at a given point in time. One can use these maps to see if weed patches are changing in a field over the course of a growing and, more importantly, if they are changing over seasons. Below is an example of a weed map that was generated using the LAS. Weed populations were monitored by determining where and when the LAS was working in a field.
Information regarding the equipment and observations collected were shared by numerous turn row meeting in 2000 and 2001. On August 1, 2000, a Precision Agriculture meeting was held in Ropesville. A classroom discussion and field demonstration took place. Information was also exchanged at the Beltwide Cotton Conferences in Anaheim, CA (2001) and Atlanta, GA (2002), and at the Southern Weed Science Society meeting in Biloxi, MS (2001) and Atlanta, GA (2002).
A light-activated sprayer was purchased in spring, 2000 and tested in numerous location and times in the 2000 and 2001 growing seasons. Initial weed data collected looked very promising, but the equipment was less effective in 2001. Moreover, this technology is still very expensive. Because the 2000 and 2001 data were somewhat different, we are anxious to see what results we will find in 2002 in both cotton and peanut production systems.
Peters, D.A., P.A. Dotray, J.W. Keeling, and J.A. Bond. 2001. Weed management in Roundup Ready Cotton using a light-activated sprayer. Proceedings of the Beltwide Cotton Conferences. P. 1223.
Peters, D.A., P.A. Dotray, J.W. Keeling, and J.A. Bond. 2001. Comparison of glyphosate applied with standard and light-activated hooded sprayers. Proceedings of the Southern Weed Science Society. 54:138.
Peters, D.A., P.A. Dotray, J.W. Keeling, J.B. Wilkerson, and H. Moody. Light-activated hooded sprayer: A two-year evaluation in High Plains cotton. Proceedings of the Beltwide Cotton Conferences. (In Press).
Peters, D.A., P.A. Dotray, J.W. Keeling, T.A. Murphree, and J.B. Wilkerson. Site specific weed management in Roundup ready cotton. Proceedings of the Southern Weed Science Society. (In Press).
Dotray, P.A., J.W. Keeling, and A.D. Brashears. 2000. Economic analysis of a light-activated weed sprayer for cotton production on the Texas Southern High Plains. International Cotton Research Center. $22,000/Funded.
Dotray, P.A. and J.W. Keeling. 2000. Economic benefit of a light-activated weed sprayer in Texas cotton production. State Support Committee. Cotton, Incorporated. $15,000/funded.
Dotray, P.A., J.W. Keeling, and A.D. Brashears. 2001. Economic analysis of a light-activated weed sprayer for cotton production on the Texas Southern High Plains. International Cotton Research Center. $25,902/Funded.
Dotray, P.A. and J.W. Keeling. 2001. Economic benefit of a light-activated weed sprayer in Texas cotton production. State Support Committee. Cotton, Incorporated. $20,000/funded.
Dotray, P.A. 2000. Cotton precision agricultural principles and equipment for weed control. District 2 Precision Agricultural Training. Ropesville, TX. August 1.
Peters, D.A. Weed management in Roundup Ready Cotton using a light-activated sprayer. Weed Science Conference of the Beltwide Cotton Conferences. Presented on January 12, 2001 in Anaheim, California.
Peters, D.A. Comparison of glyphosate applied with standard and light-activated hooded sprayers. Southern Weed Science Society. Presented on January 24, 2001 in Biloxi, Mississippi.
Peters, D.A. Light-activated hooded sprayer: A two-year evaluation in High Plains cotton. Weed Science Conference of the Beltwide Cotton Conferences. Presented on January 12, 2002 in Atlanta, Georgia.
Peters, D.A. Site specific weed management in Roundup ready cotton. Southern Weed Science Society. Presented on January 28, 2002 in Atlanta, Georgia.
Additional equipment was tested in preliminary greenhouse and field trials in 2000 and 2001. This new equipment has the potential to differentiate between plants.