Publication Date

4-1980

Advisor(s) - Committee Chair

James Worthington, W.C. Normand, Ray Johnson

Degree Program

Department of Agriculture

Degree Type

Master of Science

Abstract

The lack of adequate weed control is one of the major problems encountered in soybean production. Johnsongrass presents one of the most serious weed control problems in the Southeastern United States. numerous herbicides are used in an effort to control johnsongrass, and research is still being conducted to find new herbicides for this purpose. Two of these herbicides are BAS 9021 [6,6-dimethyl-2,4-dioxo- 3[1-[2-(propenyloxy)amino]butylidene]-cyclohexane] and BAS 9052 [2-(n-ethoxybutyrimidoyl)-5-(2-ethylthiopropy1)-3- hydroxy-2-cyclohexen-1-one].

In 1978, johnsongrass control with BAS 9021 at 1.1 and 1.7 kg/ha in sim-le early postemergence or late postemergence applications, or in each of two split applications, was evaluated using the herbicide alone, with a nonionic surfactant, or a nonphytotoxic crop oil. The split applications gave johnsongrass control ranging from 49, to 81,. Late postemergence applications of 1.7 kg/ha of BAS 9021 were as Food as split applications. As a group, the addition of oil or surfactant gave increased control over the herbicide alone.

In 1979 BAS 9021 and BAS 9052 were compared with mefluidide [N-[2,4-dimethyl-5[[(trifluoromethyl)sulfonyl]amino]phenyl]acetamide]and alachlor (2-chloro-2'6'-diethyl-N-(methoxymethyl)acetamide] for seedling johnsongrass control. The BAS materials were compared with mefluidide, trifluralin]α, α, α trifluoro-2,6-dinitro-N,N-dipropyl-p-toliuidine], fluchloralin [N-(2-chloroethyl)-2,6-dinitro-n-propyl- 4-(trifluoromethyl)aniline] and trifluralin plus vernolate [S-propyl dipropylthiccarbamate] for rhizomic johnsongrass control.

In both experiments BAS 9021 was applied at 1.1 and 1.7 kg/ha in each of two applications. BAS 9052 was applied at rates of 0.6 to 1.1 kg/ha early postemergence, late postemergence or in split applications. Mefluidide was applied at rates of 0.3 to 0.6 kg/ha either early postemergence or in split applications. All postemergence herbicide applications contained an oil concentrate at a rate of 2.4 L/ha.

Alachlor for seedling control was applied preemergence at 3.4 and 4.5 kg/ha. Preplant incorporated applications of trifluralln and fluchloralin were made at rates of 2.2 kg/ha and vernolate at 2.8 kg/ha was combined with —1 and 2.2 kg/ha of trifluraiin for rhizomic johnsongrass control.

In the seedling area, all BAS treatments gave 88% or better johnsongrass control. In the rhizomic area split applications of BAS 9052 tended to result in the best johnsongrass control. Ratings were taken both 8 and 11 weeks after planting. Soybean yields were generally better with higher johnsongrass control.

Mefluidide caused apparent soybean injury, resulted in poor johnsongrass control and lowered soybean yields. All preplant incorporated treatments gave poor johnsongrass control and low soybean yields. Alachlor gave fair johnsongrass control but resulted in high soybean yields.

Disciplines

Agriculture | Agronomy and Crop Sciences | Life Sciences | Plant Sciences | Weed Science

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