Lack of seedling vigor is a serious limitation to obtaining adequate stands of birdsfoot trefoil (Lotus corniculatus L.). Slow seedling growth makes establishment difficult because competition from weeds or companion crop plants often eliminates the young legume seedlings soon after they emerge. Gist and Mott found that birdsfoot trefoil grows much more slowly than alfalfa and red clover under identical light intensities. Seedlings not eliminated are greatly reduced in size and are susceptible to injury during the winter.

Halogeton (Halogeton glomeratus) is an introduced, poisonous annual plant which is rapidly invading the salt-desert ranges of western North America. The poisonous constituent of this plant is water-soluble oxalic acid, which varies from 17 to more than 30 percent of the dry weight in its leaves during the growing season. Because of the poisonous property of halogeton and its dense population on disturbed site, it is of considerable importance to the livestock industry.

Alarge proportion of the commonly used herbicidal substances were derived from that class of organic compounds somewhat loosely known as the substituted phenols. Many of these compounds, as well as their close relatives, have been reported to affect cell division in a number of ways. Since there appeared to be some confusion as to the type or types of effect as well as to the similarities between the effects of different members of the group, comparative studies of a number of compounds were undertaken. Two questions were considered: 1. are the cytological effects such as to suggest subtle biological hazards to organisms apparently not affected morphologically; and 2. is there a family resemblance in the cytological reaction category? Although neither question has been answered satisfactorily, the results of our studies to date are sufficiently suggestive to warrant reporting.

Need for reliable information concerning the effects of environment on the response of plants to herbicides motivated the construction of the controlled environment system described herein. A unit suitable for such studies should have these general specifications: 1. a useful range of control of light, temperature, and relative humidity; 2. no recirculation of air, to avoid overall contamination of the unit by volatile herbicides; 3. capability of maintaining several sets of conditions simultaneously; and 4. a design which may be modified easily. The system described was constructed with these points in mind.

The efficiency of cotton production has been materially increased since 1949 through the use of several pre- and post-emergence herbicides. In the high-rainfall areas, combinations of a pre-emergence herbicide such as isopropyl N–(3–chlorophenyl)carbamate (CIPC) or 3–(3,4–dichlorophenyl)–1,1–dimethylurea (diuron) with one of several post-emergence oils have given more dependable control than the use of single herbicides. In the irrigated areas, early-season weeds have been less of a problem and more attention has been given to herbicides for the control of late-appearing grasses and vines. The substituted ureas, 3–(p–chlorophenyl)–1,1–dimethylurea (monuron) and diuron, have been the most successful herbicides for this use.

4–Chloro–2–butynyl N–(3–chlorophenyl)carbamate (S–847) has been reported to show promise for selective control of wild oats in wheat, barley, flax, sugar beets, and peas. This paper presents data on the influence of several treatment conditions on wild oat control.

In considering the interaction between microorganisms and herbicides applied to the soil, two effects may become of great practical significance. One involves the potential inhibition or even germicidal action of the chemical to the microscopic inhabitants of the soil. These organisms, chiefly the bacteria, fungi and actinomycetes, occupy a unique position in biological cycles in terrestrial habitats and are essential for plant growth and soil fertility. The microorganisms decompose root and crop residues, mobilize the reserve of organic nitrogen and phosphorus, carry out transformations involving a change of oxidation state and bring about many other reactions necessary for crop production. Any deleterious influence, even of a temporary nature, could have a profound effect upon crop yields.

The table briefly summarizes research findings involving the translocation of organic herbicides and certain selected growth regulators in higher plants. Gibberellic acid, indoleacetic acid, naphthaleneacetic acid and other “on-herbicide” growth regulators are for the most part not listed except when used in experiments with the more generally accepted herbicides. For tabular information on translocation of auxins and other growth substances, the reader is referred to the Handbook of Biological Data, mentioned later. Information in the table is based on techniques which primarily utilize foliar application and for the most part does not include application via root system, injection, or bark application. As a consequence, most substances listed may be assumed to be transported predominantly in the phloem, but in numerous cases the compounds also move into the xylem.

The cotton-producing industry today faces a real challenge in its attempt to control weeds in cotton. It is a problem with many facets. Differences in weed species, topography, soil type, scale of operation, rainfall, and many other factors make it difficult to develop single practices that work satisfactorily across large areas of the Cotton Belt.

The outstanding success of 2,4-D as a selective herbicide stems from the great susceptibility of many broadleaved (dicotyledonous) weeds to the compound. Applications of 2,4-D which will eliminate many dicots will leave most grass crops relatively unaffected. Several suggestions that have been made for the differences in susceptibility between grasses and broadleaved weeds, including differences in foliar absorption, restricted translocation of the compound in grasses, and differences in detoxification of the 2,4-D molecule.

Barnyardgrass (Echinochloa crusgalli (L.) Beauv.) is the most serious weed in rice in Arkansas and this and other species of Echinochloa are a serious problem throughout the rice-growing areas of the world. A limited field survey conducted in August 1957 in the Grand Prairie rice-growing region of Arkansas indicated that 27 percent of the rice fields were infested with barnyardgrass. Presumably the yield of rice on these fields could have been increased substantially by controlling the barnyardgrass.

Although Russian knapweed is not as widespread as some of the other deep-rooted perennial weeds, thousands of acres of farmland are infested and it is spreading. It is generally called Centaurea repens L., according to Fernald and Stevens, though it also is referred to as C. picris Pall. Stevens states that there is some question about the identity of C. repens.

The recognition of the herbicidal activity in the phenylacetic acids by Pybus et al. is a matter of particular interest to those whose work is concerned with weed control in crops unusually sensitive to 2,4-D (2,4-dichlorophenoxyacetic acid) and its derivatives.

The concept of reducing tillage operations with herbicides was first tested in California orchards in 1944. In 1949, Johnston and Sullivan gave a detailed discussion of chemicals and equipment needed for eliminating tillage in orchards. Over a 4-year period chemical weed control proved cheaper than cultural methods. Soil condition and water penetration were improved and soil erosion was reduced by chemical weed control.

The first step in a satisfactory forage-legume program on the farm is the establishment of the legume. Success or failure here can mean the difference between a continued efficient rotation system and a financial loss. Many farmers have been reluctant to plow up old seedings at the proper time because of the cost of new seedings and the possibilities of seeding failures. Also, new seedings may appear successful in the seeding year only to be lost during the first winter. This paper is a report of 3 years' study at Ithaca, New York, on the use of herbicides applied pre-emergence to aid in the establishment of forage legumes without a companion grain crop.