Cotton Response to Preplant Applications of Quinchlorac

H. R. Hurst


Quinchlorac (Facetr) is a rice herbicide first available to growers in 1993. Because of the residual nature of this compound and the close proximity with which cotton is grown in some portions of the Mississippi Delta, an experiment was conducted in 1991 and 1992 to evaluate the residual effects from the application of this herbicide on land subsequently planted to cotton. The experiment was a three by two by four factorial arrangement on a randomized complete block design with three replications. Factor A was three application timings: early, 35 days before planting in 1991 and 26 days in 1992; intermediate, 19 days before planting in 1991 and 16 days in 1992; and late, 4 days before planting in 1991 and at planting in 1992. Factor B was tillage immediately before the application of Facet using a hipper and the operation of a bed conditioner immediately afterward or Facet application on a previously hipped bed. Factor C was the rate of Facet. The use rate range is 0.25 to 0.5 lb ai/Acre. The rates utilized were 0.375 lb ai/A, 0.1875 lb ai/A, 0.09375 lb ai/A, and a no treatment control. The entire area was subsoiled in late November 1990 and was hipped on March 11, 1991 and March 4, 1992. The entire area was rehipped on the day of planting and a bed conditioner was operated just afterward. DES 119 cotton was planted with a John Deere 7100 planter on May 7, 1991, and May 1, 1992. The area was treated preemergence with Cotoranr 85DF at a broadcast rate of 1.25 lb ai/A applied to a 20-inch band centered over the row. The quinchlorac treatments were applied to the same plots in 1991 and 1992. Information was obtained on the treatment effect on cotton plant height, cotton stand, visual cotton injury, and seed cotton yield. The reaction to the various treatments was different each year, therefore the information obtained was not pooled over years. In 1991, Factor B involving tillage before the application of quinchlorac had a minor and inconsistent effect on cotton height. An early reduction was experienced (1.4 cm) but a later height determination showed an increase of 4.4 cm where no tillage was performed before the application of quinchlorac when averaged over the three dates of application. The estimated visual injury in June and in late July resulted in 10% and 13% increased injury when the application of quinchlorac was made immediately after tillage. The injury ratings, however, were not high enough to suggest permanent injury. Tillage before the application of quinchlorac did not affect yield in 1991.

Cotton plant height was reduced with the application of Facet from the earliest to the latest application time (Factor A) when averaged over tillage and application rates. The number of cotton plants per acre was also reduced significantly by each of the application timings as they approached planting. However, the lowest plant count on July 1 was 38,100 plants/acre which is not considered to be low enough to affect yield. Visual crop injury also increased as the time to planting was decreased. However, the injury by the last of July was only 7% for the early and intermediate application timings, and 23% for the late timing. A visual estimate of crop maturity was made in mid-September (at a value of 5 indicating maximum boll opening whereas 0 equals no opening) resulting in less open cotton by each of the planting dates from early to late. The seed cotton yield on first pick was not different with the early and intermediate application timings but was less with the late application timing. The total crop yield was higher for the intermediate plant timing than for either the early or late timing of quinchlorac application. Percent first harvest was lower with the late application timing.

In 1991 when the Facet rate (Factor C) increased from 0 to 0.375 lb/A, the plant height was decreased when application was above the 0.1875 rate, the visual injury was increased, the cotton stand was decreased, the crop maturity was decreased, and the crop yield at first harvest was decreased. The total yield and percent first harvest were not decreased except with the 0.375 rate.

Again in 1992 there was very little affect from the application of quinchlorac applied immediately after tillage of preformed seedbeds vs. no tillage of the beds. On August 3, the visual estimate of cotton injury was only 16 and 10% respectively for treatments were quinchlorac was applied to beds with or without tillage.

When the time of application before planting was reduced from early to late in 1992, cotton plant height was reduced by each of the timings when evaluated in late May but were not different when evaluated in late June. The cotton stand was reduced with the late application as determined in mid-May but there was no difference in any of the timings on plant stand by late June. The cotton stand was above that which would be considered to influence yield. The visual estimate of cotton injury in May and June of 1992 resulted in less injury with the late application. By August 3, the highest injury was only 18% with the early application date. On August 31, 1992, visual estimate of maturity was less with the medium and late applications before planting. The seed cotton yield was lower from the late application date than from the early application date.

When the affect of quinchlorac rate was evaluated on cotton height in late May, cotton plants were shorter with the lowest and intermediate rates of quinchlorac than when no quinchlorac was used. The highest rate of quinchlorac resulted in increased shorter cotton plants. This same relationship resulted from late June measurements, however, the lowest rate of quinchlorac was no different statistically than where no quinchlorac was used even though numerically it was slightly less. The cotton stand was evaluated in mid-May, late-May, and late-June. In mid- and late-May the highest rate reduced stand compared to no quinchlorac. When stand was determined in late-June, the intermediate and high rates of quinchlorac were different from the low rate and no quinchlorac application. The visual estimate of cotton injury in May and June was greater as the rate was increased. By August 3, the highest rate of quinchlorac resulted in an estimated injury rating of 33% which was higher than the intermediate rate which in turn was higher than the lowest rate or no quinchlorac. The visual estimate of cotton maturity on August 31 indicated that plots with the highest rate had less open cotton as compared to the other three application rates. The highest rate of quinchlorac produced a significantly lower yield of seed cotton (450 lb/A) in 1992.

Reprinted from Proceedings of the 1994 Beltwide Cotton Conferences pg. 1701
©National Cotton Council, Memphis TN

[Main TOC] | [TOC] | [TOC by Section] | [Search] | [Help]
Previous Page [Previous] [Next] Next Page
Document last modified Sunday, Dec 6 1998