Generally, 2,4–Dichlorophenoxyacetic acid (2,4–D) has performed well as a selective herbicide for sweet corn. Sometimes, however, applications of 2,4–D presumably at recommended dosages have resulted in abnormal plant behavior. In certain instances reduced yields have resulted.

The research worker who attempts the application of herbicides to a small area in such a way as to simulate general practice, is faced with a unique problem. The ultimate objective is to apply the chemical to as small an area as is feasible but in such a way that it will correctly represent what the activity on both weeds and crop plants would have been had the application been made on an acreage basis. Small plots are desirable if land or labor are limited, if expensive crops in farmers’ fields are being used, and particularly when the chemicals may be highly toxic, or the activity is unknown.

With the advent of herbicides, a new tool has been made available for studying the effect of soil physical properties on crop growth. This new tool may be used for solving such problems as “What are the beneficial effects, if any, accruing from cultivation for the control of weeds?” “Is cultivation necessary for maximum production?”

Zimmerman has summarized the plant hormone activity of trichlorobenzoic acid and various substituted derivatives. The effects have been found to be formative in nature.