The discovery of the herbicidal properties of the phenoxyalkylcarboxylic acids created an impetus in research on the development of new herbicides. A number of these compounds are now being used commercially as pre-planting, pre-emergence, and post-emergence treatments for the control of dicotyledonous and monocotyledonous, annual and perennial weeds in a variety of weed-crop situations.

The toxicity of the substituted urea herbicides may persist in the soil for considerable periods following treatment. Consequently, they have been used extensively as pre-emergence and post-emergence herbicides and as soil sterilants. In the drier regions of the western states injury to cereals may occur when they are seeded in the fall following cotton which has been treated with the substituted ureas to control weeds. Because of the nature of these compounds and because of their rapid acceptance as herbicides, much interest has developed in relation to their breakdown in the soil.

Studies with plant growth-regulators are severely handicapped unless methods are available for quantitative determinations of these chemicals. Beginning with the classical work of Went, several techniques have been developed to obtain a quantitative measure of plant growth-regulating chemicals. Brown and Weintraub, Hitchcock and Zimmerman and Frankton have discussed the use of biological assays as quantitative tests for various hormone-type chemicals. Thus far, the only biological methods developed beyond the semi-quantitative stage are those depending on cell elongation in shoots, inhibition or elongation of roots, and the stimulation of ovary development.

The granular herbicide distributor described here was devised to satisfy the need for equipment that would spread the clay type of granular carrier with a high degree of accuracy in small plot field trials. Performance data and construction details are presented for the benefit of others doing research on granular herbicides.

The moisture content of soils is frequently reported to have an important effect upon the phytotoxicity of herbicides. Yet, specific experimental results establishing such relationships are, for the most part, lacking. Most moisture studies with herbicides have been designed to evaluate the effect of applied water on leaching and its indirect effect on volatilization and breakdown by exposure to sunlight. Some studies have shown the effect of moisture content on the rate of herbicide breakdown. Research on the fate of herbicides in soils has been summarized by Hill et al. and Ogle and Warren. The experiments reported here were designed to establish the effect of soil-moisture content per se upon the response of cotton to 3–(3,4–dichlorophenyl)–1,1-dimethylurea (diuron), isopropyl–N–(3–chlorophenyl) carbamate (CIPC) and 4,6–dinitro ortho secondary butylphenol (DNBP) as the alkanolamine salts.

Bear oak (Quercus ilicifolia Wang.) is widely recognized as difficult to eradicate. Burning, cutting, and routing, while killing the original stems to the ground, have caused dormant buds on the root collar to become active and produce fast growing sprouts which soon replace the original plant. In fact, single-stemmed plants so treated can produce as many as 40 or more new stems. Moreover, this species has been difficult to control chemically owing to resurging growth from the root collar and lower stem after a kill of original stems. Bear oak is widely distributed as an understory tree in the eastern United States extending from Maine to North Carolina and from the Atlantic Coast to Ohio and Kentucky. Often it develops into dense thickets on burned-over forest land or abandoned fields so that it monopolizes the site, crowding out other more desirable species and making planting of other trees an expensive operation. One hundred and fifty to two hundred thousand acres of such “scrub oak barrens” occur in Pennsylvania.