Economics of Postemergence Johnsongrass Control in Cotton

E.P. Webster, M.G. Patterson, and Bobby Norris


 
ABSTRACT

Field research was conducted in 1987 through 1989 at the Tennessee Valley Substation, Belle Mina, Ala., to determine the cost and control provided by various grass herbicide systems for cotton (Gossypium hirsutum). A randomized complete block design with four replications was used. Plot size was four rows wide (40" between rows) and 20 ft long. Five pounds of johnsongrass (Sorghum halepense) seed per acre were spread and lightly incorporated before planting, and one rhizome per 6 ft of row was planted before the cotton (DPL 50) emerged. All treatments except the weedy-check and the hoed-check received fluometuron (1.5 lb/A) preemergence, and cyanazine plus MSMA (0.75 + 1.5 lb/A) post-directed, for general weed control. Johnsongrass control treatments included trifluralin PPI alone or trifluralin plus one postemergence application of either fluazifop, sethoxydim, or quizalofop, and trifluralin plus two applications of either of the three aforementioned herbicides. All postemergence herbicides were applied on a 16" band at recommended rates and times. Cultivation was used in all plots except for weedy and hoed-check.

Johnsongrass control in 1987 was comparable across all treatments (80-90%). Likewise, seed cotton yields were statistically equivalent across grass herbicide treatments, averaging 2166 lb/A. In 1988 and 1989, johnsongrass control differed due to the more extensive rhizome production that developed from the previous year. Trifluralin alone at 0.5 lb/A ($3.00/A) provided 80 and 20% control, and yielded 1594 and 0 lb/A in 1988 and 1989, respectively. Trifluralln plus a single application of any grass herbicide (average cost of $13.90/A) provided 94 and 92% control, and yielded 1848 and 3173 lb/A In 1988 and 1989, respectively. Trifluralin and two postemergence grass herbicide applications (average cost of $22.28/A) provided 95 and 96% control, and yielded 1815 and 3188 lb/A in 1988 and 1989, respectively. In conclusion, trifluralin and one application of any postemergence grass selective herbicide provided a cost effective treatment.



Reprinted from 1990 Proceedings: Beltwide Cotton Production Research Conferences pg. 356
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998