Masters Theses

Date of Award

12-1967

Degree Type

Thesis

Degree Name

Master of Science

Major

Agronomy

Major Professor

Henry Andrews

Committee Members

Larry Skold, H. D. Swingle

Abstract

Johnsongrass (Sorghum halapense L. ) was first introduced into the United States from Turkey in 1830 hy Governor Means of South Caro-lina. Colonel William Johnson was the first to cultivate the grass extensively and it was named for him (27). Although some economic uses have been found for Johnsongrass, it has become one of the most serious weeds in row crops in the southern states. Johnsongrass is usually found on the better farmland in Tennessee and is usually in direct competition with corn (Zea mays L.), cotton (Gossypium hirsutum L.), and soybeans (Glycine max B.), the major agronomic crops of this state. The rapid rate of seed production and the persistence of viable seed in the soil enable Johnsongrass to spread by seedlings even after rhizomes have been almost eradicated (29). This unique character of Johnsongrass has made it one of the most despised weeds in the South. Another characteristic of Johnsongrass which makes it trouble-some in crop production is that it usually emerges early in the spring and grows at the same time as corn and cotton. Since both corn and cotton must be planted early in order to obtain high yields, Johnson-grass competes directly with them. Studies by Overton and Andrews (28) indicated that repeated diskings of fallow soil reduce the number and vigor of Johnsongrass rhizomes; however, these practices do not allow for the growth of a crop. Either mechanical or chemical fallow will prevent any crop from being grown concurrently in the treated area, thus eliminating income from the area. The objective of this experiment was to determine the possi-bility of controlling Johnsongrass effectively by chemical or mechanical means or by a combination of the two and, at the same time, producing corn, cotton, and soybeans economically.

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