Crop production on most lands of the western United States requires the use of supplemental water which is delivered through established irrigation canal distribution systems. These systems frequently support heavy growths of aquatic plants which prevent or impede the passage of water. Because a reduction in the carrying capacity of a canal makes it necessary to deprive potential productive land of the water required to grow a satisfactory crop, it is imperative to keep the waterways open.

The following table of chemical and physical properties of some herbicides was compiled as an aid to agricultural research workers.

When wheat seedlings are injured by trichloroacetate (TCA) the leaves turn yellow in much the same manner as do those on plants growing in media where the nutrients are unbalanced. Accordingly, there is the possibility that TCA may have some effect on the intake of plant nutrients, and that injury was actually the result of nutrient starvation.

The fate of herbicides in the soil is of great importance to both research workers developing chemical weed control methods and to growers employing these newer techniques. It is desirable to know whether herbicides applied to the soil will persist and be cumulative so that subsequent crops will be affected, if a short period of residual activity can be expected, or if the compounds are rapidly dissipated. In case of pre-emergence applications where timing is critical and results vary with such factors as soil type, moisture and temperature, the activity and persistence of a herbicide are of great importance. Thus it seemed pertinent to study the effects of soil type, exchange capacity, temperature and amount of rainfall on breakdown, leaching and retention of certain herbicides in the soil. The herbicides used were 2,4–dichlorophenoxyacetic acid (2,4–D), N–1 naphthyl phthalmic acid (NPA), trichloroacetic acid (TCA), 3–(p–chlorophenyl)–1, 1–dimethylurea (CMU) and isopropyl N–(3–chlorophenyl) carbamate (CIPC).

The action of trichloroacetate, a herbicide of grass-type plants such as quack grass and Johnson grass, has been studied for several years by observing the morphological responses of treated plants. Its presence in such plants has been indicated by analyses for the trichloromethyl group with a colorimetric test using pyridine and sodium hydroxide (1, 10). A review by Barrons and Hummer (1) indicates that root absorption is a much more important avenue of entry than foliar absorption. They also report differences in TCA content in the expressed sap of several species of treated plants. At 20 lbs. per acre they found “very little” TCA in corn and beans (both TCA-susceptible). At 10 lbs. per acre, they found “not a trace of TCA” in corn, “very little” in beans, but “a relatively high concentration of TCA” in peas (a relatively TCA-tolerant plant). However, Tibbitts and Holm (10) found 100 to 500 μg. of TCA per g. of fresh snap bean tissue from plants whose culture solutions contained 15 mg. of commercial grade 80% TCA as sodium salt per 150 ml. of nutrient. In order to check these observations, and to see whether TCA itself is present in the plants, and if so to determine the pattern of its distribution within the plants, as well as to look for possible metabolic products, C14-labeled TCA was synthesized and used in tracer experiments with corn and pea plants.

During the course of investigation of the activity of some organic compounds selected for potential herbicidal effects (5), many candidates appeared to have activity equal to that of the standard 2,4–dichlorophenoxyacetic acid (2,4–D), while a few appeared to be more active. One of the latter was p–fluoro–o–toloxyacetic acid, which was first prepared by M. S. Newman (3).

One of the most important of the numerous difficulties involved in the successful production of cotton is that of controlling weeds. The fertile soils and humid seasons generally occurring in the Delta, provide optimum conditions for abundant weed growth. During 1951, Missouri cotton producers spent approximately $10,000,000 for hand-labor alone in the production of a $69,000,000 crop. With the exception of Johnson grass (Sorghum halepense L.) and some perennial vines, annual weeds (particularly grasses early in the season), are most troublesome. By far the worst offender under the conditions of the 1951 through 1953 experiments was crabgrass (Digitaria sanguinalis L. (Scop.).