Weeds are plants that grow along with cultural plants, both groups making up a community. The prevalence of weed species becomes adjusted to cultural management practices and often, they are not able to survive without their cultivated counterpart. In this way, some weeds become more or less domesticated plants (e.g. Bromus secalinus L.).

Recently sodium trichloroacetate (TCA) has come to the front as a useful herbicide for the control of annual or perennial grasses. The object of this paper is to report the persistence of the chemical in different types of soils as related to time and rates of applications.

The current widespread use of ester and amine formulations of 2,4–dichlorophenoxyacetic acid (2,4–D) and/or 2,4,5–trichlorophenoxyacetic acid (2,4,5–T) has made apparent the potential vapor hazard of these herbicides in their injury to susceptible crop plants growing nearby. A method used for evaluating the volatility of proprietary formulations was reported previously (1,2) using temperatures of 70° to 75° F. At this “normal” temperature eighty commercial ester preparations representing thirty-one different formulations of 2,4–D and/or 2,4,5–T showed, conclusively, that esters such as the isopropyl, butyl, ethyl, amyl, and pentyl individually or in mixture were volatile; and the iso-octyl, butoxyethanol, tetrahydrofurfuryl, polypropylene glycol, and propylene glycol butyl ether esters were low volatile. These formulations do not comprise all the commercial preparations tested but are given only to indicate the extent of volatility found for 2,4–D and 2,4,5–T ester herbicides commonly available on the market.

The synthesis of C14 carbonyl labeled 3–(parachlorophenyl)–1, 1–dimethylurea (CMU) was undertaken to provide a supply of the herbicide for use in studies of its mode of action and of its retention in the soil.

Water, especially water used for irrigation, has been adjudged for many years an important agent in the dissemination of weed seeds. Egginton and Robbins (7) found a total of 81 different species of weeds in 156 weed seed catches from three different ditches during 1918 and 1919 and determined that the number of weed seeds passing a given point on a ditch which averaged 12 feet in width during a period of 24 hours may reach several millions. Hope (11) analyzed a considerable number of weed seed catches from irrigation channels during 1924 and 1925. He computed that 1,674,030 seeds of 13 different weed species which occurred on the surface and to a depth of 1.57 inches in one 10-foot ditch passed during a 24-hour period on September 2, 1925. Further computations illustrated that the flow of weed seeds would amount to a deposition of 170,800 seeds per acre of land in one 6-inch irrigation. The latter computations were based on the assumption that the seeds were distributed uniformly over the cross section of the ditch at the point of catch.

Sugar cane appears to be suitable for the use of 2,4–D sprays for selective weed control. According to Young (1952) this is a regular commercial practice on some of the large plantations in Puerto Rico. The operators of certain plantations in Peru have found the application of 2,4–D to be economically practicable for broad-leaved weed control. Best and Gibbens (1951) have reported the value of 2,4–D sprays for sugar cane in Louisiana.