Weed control during the fallow year and yields of subsequent winter wheat (Triticum aestivum L.) were lower on unsprayed plots than on plots treated with 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) at 2 lb/A or 3-amino-l,2,4-triazole (amitrole) at 1/2 lb/A plus 3-(p-chlorophenyl)-l,l-dimethylurea (monuron) at 1 lb/A. The moldboard plow gave the most effective weed control in the winter wheat-fallow rotation followed by the oneway and the sweep plow. Sweep plow tillage left the greatest amount of plant residues on the soil surface to prevent wind and water erosion, but it did not consistently destroy shallow-rooted downy brome (Bromus tectorum L.) plants. Average downy brome stands in winter wheat on fallow plots tilled with the sweep plow, oneway, and moldboard plow were 331, 114, and 16 plants per 54 sq ft, respectively. Winter wheat yields averaged for the sweep plow, oneway, and moldboard plow treatments were 17, 18, and 20 bu/A, respectively. The most feasible method of controlling weeds in a winter wheat-fallow rotation, found in this study, was oneway tillage in combination with the lower herbicide rates.

Germination, growth, and potential phytotoxicity of sicklepod (Cassia obtusifolia L.) were studied. Seed germination occurred in the temperature range from 18 to 36 C, but rapid seedling growth occurred only between 30 and 36 C. Seed dormancy caused by a waxy coat resulted in only 15% germination in soil over a 12-month period. A 1:15 (g/ml) water extract of sicklepod tops inhibited germination of cotton (Gossypium hirsutum L.) and oat (Avena sativa L.) seed. Incorporation of sicklepod residues in soil reduced germination of cotton seed but increased persistence of sericea (Lespedeza cuneata (Dumont) G. Don.) and crimson clover (Trifolium incarnatum L.) because damping-off was almost eliminated. There was evidence in nutrient cultures that sicklepod released a phytotoxic residue from its roots, reducing growth of cotton but having no effect on soybeans (Glycine max (L.) Merr.). Sicklepod grew well in soils ranging from pH 3.2 to 7.9. Sicklepod response to N, P, and K levels was similar to cotton and higher than that of soybeans.

The development of amylase activity controlled by the embryo in the distal halves of intact barley (Hordeum vulgare L., var. Larker) seeds during the first 2 days of germination was prevented by the presence in the culture solution of 10−4 M 7-oxabicyclo-(2.2.1)heptane-2,3-dicarboxylic acid (endothall), 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil), 2,6-dichlorobenzonitrile (dichlobenil), or 3 amino-2,5-dichlorobenzoic acid (amiben) and was not overcome by the simultaneous addition of gibberellic acid. The aforementioned herbicides did not inhibit gibberellic acid-induced amylase synthesis in de-embryonated halved barley seeds. The amiben and bromoxynil inhibition of barley germination was slightly reduced by the simultaneous addition of 10−2 M glucose to the culture solution. Amiben and bromoxynil also inhibited the development of low levels amylase activity found in 2-day-old squash (Cucurbita maxima Duchesne, var. Chicago Warted Hubbard) cotyledons; however, added benzyladenine overcame the inhibition. In contrast to barley, benzyladenine was shown to induce the development of amylase activity in squash. Tolerance of squash and other seeds low in carbohydrates to amiben and bromoxynil during germination may be related to their independence from herbicide-inhibited carbohydrate degradation for energy and carbon source required for anabolic processes.

Excised leaves of Canada thistle (Cirsium arvense (L.) Scop.) ecotypes and bean (Phaseolus vulgaris L., var. Red Kidney) metabolized 3-amino-l,2,4-triazole-14C (amitrole) to the same radiolabeled products, but they were produced at different rates as shown by thin-layer and paper chromatography. Bean leaves metabolized amitrole to a metabolic product (Unknown II) probably β-(3-amino-1,2,4-triazolyl-1-) α-alanine approximately three times taster than Canada thistle leaves, while Canada thistle converted Unknown II to another product (Unknown I) about 10 times faster than did bean. Thus Unknown II accumulated in bean, and Unknown I in Canada thistle. This reaction sequence in Canada thistle was evidently an irreversible consecutive first order reaction. A difference in the rate of metabolism was observed between susceptible and resistant ecotypes of Canada thistle.

Chromatographic procedures were developed for use in the laboratory studies of the breakdown of N-(p-bromophenyl)-N′-methoxy-N-methoxyurea (metobromuron) in soils. Both thin-layer and gas chromatographic procedures were developed to determine the known and/or suspected metabolic products occurring from the microbiological transformations in soil. Extraction of 3 soils, after 5 days of equilibration, yielded all the metabolites. Neither the gas chromatographic or thin-layer procedures were affected by soil extractives.

The gross morphological effects of the herbicide 4-methyl-sulphonyl-2,6-dinitro-N,N-dipropylaniline [nitralin] on roots of corn (Zea mays L., var. U. S. 13) suggested abnormal cytological behavior. Roots of corn plants treated preemergence with nitralin developed digitate to globose swelling in the region of active cell division of the root tip. Cytological examination of the affected area showed that the effects of the herbicide were prevention of cell wall formation, enlargement of cells, and extensive replication of nuclei, and suggests that a primary effect of nitralin is on cell division and that this may be a primary mechanism of action as a herbicide.

A 3-year ecological study of physical, chemical, and biological factors affecting the growth of submersed aquatic weeds was conducted in four irrigation and drainage canals in south Florida. Growth of aquatic vegetation was influenced by light intensity which decreased in a geometric ratio to water depth. The light penetration into the water was influenced by dissolved coloring matter and turbidity. A high concentration of nitrogen was found in three of the canals. Nitrogen entered the canals as sewage effluent discharged into the water and as fertilizer runoff from surrounding farmland. Density of aquatic vegetation harvested at intervals of 6 months from clipped plots varied from zero in a newly dug canal to 22,000 lb green weight/A in an old established canal. During the 3-year study, there was a complete shift of the vegetation from southern naiad (Najas guadalupensis (Spreng.) Magnus) to Florida elodea (Hydrilla verticillata Casp.) in two of the canals, but there was no change in plant species in two canals. No other chemical and physical factors evaluated in the study limited submersed aquatic weed growth in these canals.

Several factors were studied which influenced 3-amino-1,2,4-triazole (amitrole) metabolism in excised leaves of bean (Phaseolus vulgaris L., var. Red Kidney) and Canada thistle (Cirsium arvense (L.) Scop.) ecotypes. Amitrole metabolism in the leaves of both species held in the light was greater than in leaves held in the dark. Increasing the temperature from 15 C to 28 C also stimulated the rate of metabolism of amitrole. However, this effect was much less pronounced when the temperature was increased from 22 C to 28 C. Dipping the leaves in 10−2M ammonium thiocyanate reduced the metabolism of amitrole, whereas similar pre-treatment with 3.5 × 10−3M 6N-benzyladenine enhanced the metabolism of amitrole.

The Weed Science Society of America operates a placement office as a service to its members. Listings of “Positions Desired” and “Positions Available” received each 3 months by Orvin C. Burnside, Chairman, Manpower Placement Service of WSSA, Department of Agronomy, University of Nebraska, Lincoln, Nebraska 68503 are published in Weed Science. Once a listing is published it is then discarded. If one wants a listing rerun it will have to be resubmitted. One man from each state and province is asked to provide “Positions Available” and “Positions Desired” for his area once every 3 months. Individuals or companies also may send the necessary information directly to O. C. Burnside.

Chemical-fallow experiments were initiated as a possible means of improving summer-fallow procedures for seedbed preparation and rehabilitation of abandoned croplands subject to wind erosion. Red threeawn (Aristida longiseta Steud.) and sand dropseed (Sporobolus cryptandrus (Torr.) Gray) are pioneer perennial grasses that have stabilized these sandy loam soils but are undesirable forage plants. Dimethylarsinic acid (cacodylic acid), 2-tert-butylamino-4-ethylamino-6-methylthio-5-triazine (GS-14260), and a mixture of 3-amino-l,2,4-triazole (amitrole) plus ammonium thiocyanate were ineffective, but 2,2-dichloropropionic acid (dalapon) applied at 6 lb/A or more reduced these pioneer perennial grasses 80 to 100%. Follow-up treatments, either mechanical or chemical, are needed to maintain control of competing vegetation while seeded species become established.

Degradation of 3-amino-l,2,4-triazole-5-C14 (amitrole-5-C14) in autoclaved, potassium azide, ethylene oxide, and dry-heat sterilized soil was compared with that observed in nonsterile soils by measuring evolved C14O2. Amitrole degradation occurred in azide and ethylene oxide-sterilized and nonsterile soils but not in autoclaved soils. Only slight degradation occurred in autoclaved soil re-inoculated with mixed cultures of soil microorganisms isolated from soil in which amitrole had been rapidly degraded. Addition of EDTA-Na to nonsterile and ethylene oxide sterilized soils reduced amitrole degradation. Addition of organic amendments to amitrole treated soil stimulated microbial activity but reduced amitrole degradation. Addition of specific metallic salts to certain soils increased the rate of amitrole degradation. Amitrole degradation occurred rapidly in several free radical generating chemical systems. These results and additional observations indicate that amitrole degradation, at least in three soils examined, was largely a chemical process, and that microbial involvement was only indirect.

Dr. F. L. Timmons, of the USDA Agricultural Research Service, was in Somalia, Africa, March 21 to April 17, 1968 on an assignment with the Wyoming University USAID Program in that country. While in Somalia, he surveyed weed problems in irrigation canals and irrigated cropland, initiated several control experiments with herbicides, and conferred with Wyoming and Somali scientists and specialists on a program for weed control.

Research Biologist to do field research on agricultural chemicals. Maintain liason with research scientists in southern U.S.A. Travel time 20%. Living area Little Rock, Arkansas. Salary open. Ph.D. in one of biological sciences and 2 to 5 years experience. Age 25 to 35. Ability to establish research programs and assume direction of research establishment with cooperating institutions. New position. Contact K. L. Hill, Air Products 8c Chemicals, Inc., P. O. Box 538, Allentown, Pa. 18105.

We studied the uptake of ethyl N,N-dipropylthiocarbamate (EPTC) by barley (Hordeum vulgare L.), wheat (Triticum aestivum L.), oats (Avena sativa L.), sorghum (Sorghum vulgare Pers.), and giant foxtail (Setaria faberii Herrm.) using a double plastic pot technique that allowed separate exposure of the shoot and root zones to treated soil. Barley was more tolerant than wheat, whereas oats, sorghum, and giant foxtail were the most susceptible to EPTC at 1/4 to 1 1/2 lb/A-inch. The roots were the major site of uptake in barley, but injury to the other species from root exposure was equal to or slightly less than that from shoot exposure. The seed, or first 2 to 4 mm of shoot or both, were more sensitive in wheat than in barley. Such differential sensitivity was not evident in the shoot zone of the other species. These experiments, coupled with 14C-EPTC studies, indicated that differences in tolerance can be associated with the sites of uptake.

The fundamental unit of the metric system is the METER (the unit of length) from which the units of mass (GRAM) and capacity (LITER) are derived; all other units are the decimal subdivisions or multiples thereof. These three units are simply related, so that for all practical purposes the volume of one kilogram of water (one liter) is equal to one cubic decimeter.

Dr. S. Robert Colby, formerly of the Agronomy Department, University of Maryland, now is located at the Crop Protection Institute, Durham, New Hampshire. In his new location, Dr. Colby is in charge of the herbicide screening and development program conducted there.