weed science
BP-10-5
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • DEPARTMENT OF BOTANY AND PLANT PATHOLOGY LILLY HALL OF LIFE SCIENCES • WEST LAFAYETTE, INDIANA 47907

EQUIPMENT USED FOR INCORPORATING HERBICIDES T.N. Jordan, Extension Weed Specialist

Preplant incorporated herbicides are used on many acreages of agronomic cropland in the Midwest. Many of these herbicides are incorporated out of necessity, while others are incorporated to reduce their dependency upon rainfall for activation. The most widely-used tool for herbicide incorporation is the tandem disk. Its popularity stems from its availability and multifacet use as a conventional tillage tool. In recent years, tillage systems have changed, and also new and different kinds of tillage and incorporation equipment have been developed. With these factors to consider, a new look at the overall approach to herbicide incorporation should be made.
The choice of equipment and method of incorporation, like the choice of herbicides to use for a particular weed problem, must fit the overall production system. No one tool or method of incorporation is best for all situations. Factors such as roughness of the soil surface, soil moisture and soil type may play a bigger role in the success of herbicide incorporation than the tillage tool used for the incorporation. However, when used properly, most any tillage too can give adequate soil incorpora-tion of herbicide in a variety of soil and conditions.

The incorporation process involves two types of herbicide distribution:
horizontal and vertical. Both distribu-tion types must be achieved for uniform herbicide placement and adequate weed control without causing crop injury.

Two Pass Incorporation Tools

Tandem disk harrows invert soil similarly to a moldboard plow. They also tend to place herbicide deeper in the soil than most other incorporation tools.

Travel speed and operating depth have the greatest effect on vertical placement of herbicides that are incorporated with a disk. Increasing the speed incorporates to a shallower depth and increasing operating depth incorporates to a deeper depth. Large disks operated at 4 inches or less do not make sufficient soil contact to properly invert the soil and result in very little soil mixing. When operated at depths of 6 inches or greater, herbicides are incorporated too deeply. Disk blade spacing and depth of operation seem to be more important than blade diameter in determining soil mixing. Research at the University of Illinois has shown that small disks (blades less than 22 inches and 7	1/2 inches apart) work
better than large disks (blades 22 inches or greater and 9 inches or more apart). Herbicides are generally incorporated one-half to three-quarters, the operating depth of the disk, which is normally about 4 to 5 inches. The Illinois research, involving granules coated with a fluorescent dye, showed that 89 percent of the granules were in the top 3 inches of soil after one pass with a disk. After two passes, the granulars moved deeper with only 74 percent in the top 3 inches.
Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U.S. Department of Agriculture Cooperating. H.G. Diesslin Director, West Lafayette, IN. Issued in furtherance of the Acts of May 8 and June 30, 1914. It is the policy of the Cooperative Extension Service of Purdue persons shall have equal opportunity and access to its programs and facilities without regard to race, religion, color, sex or national origin.