The amount of C14-labeled triazine herbicides absorbed by the upper and lower surfaces of peanut (Arachis hypogea) leaves was found to be significant with the exception of 2-methoxy-4,6-bis(isopropylamino)-s-triazine (prometone). Almost always a surface active agent increased the absorption of triazine herbicides by the leaves. The surface active agent did not play any role in diffusion of these herbicides. Among the four herbicides tested 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) and 2-methoxy-4,6-bis(isopropylamino)-s-triazine (prometone) were found to move both acropetally and basipetally, whereas 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) and 2-chloro-4,6-bis(isopropylamino)-s-triazine (propazine) moved only in the acropetal direction.

Direction and rate of translocation of sucrose* from urea* 2,4-D* (2,4-dichlorophenoxyacetic acid) and amitrole* (3-amino-l,2,4-triazole) were toward regions of active growth. In oak seedlings translocation was slower than in cotton seedlings. In oak seedlings growing leaves and shoots constitute active sinks toward which tracers move. Sucrose* from urea* translocates freely; 2,4-D* moves less freely because of accumulation enroute; amitrole* is intermediate between these. High humidity induces rapid and extensive uptake of tracers by oak seedlings; the increase over normal transport is mainly in the xylem.

Ford soybean yields and weed yields were studied under combinations of tillage treatments, 3-amino-2,5-dichlorobenzoic acid (amiben) applications, hand weedings, and row spacings on irrigated and non-irrigated locations in Nebraska during 1961 and 1962. Soybean yields increased and weed yields decreased with tillage, amiben applications, hand weedings, and narrow-row spacing of soybeans. Combinations of these weed control treatments gave more dependable results than any one alone. Each 86 lb/A of weeds present produced an average soybean yield reduction of 1 bu/A. Advantages of growing soybeans with amiben applications in 10-inch rows as compared to 40-inch rows are: (a) an average soybean yield increase of 39%, (b) elimination or reduction of tillage (c) a 50 to 75% reduction in amiben application rate, and (d) little or no soybean injury from the lower rates of amiben required in the 10-inch rows.

Seed of common cattail (Typha latifolia L.) germinated 100 percent when the blunt ends of the seed coats were ruptured. Seedlings developed primarily while submersed in water. Growth of the seedlings was rapid. A single plant in 6 months developed a network of rhizomes covering an area 10 feet in diameter. Pistil-late spikes 7 inches long produced an average of over 222,000 seeds.

Greenhouse experiments showed that monuron, 3-(p-chlorophenyl)-1,1-dimethylurea, uniformly applied to the soil surface immediately after planting, was about twice as toxic to seedling cotton as was diuron, 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Phytotoxicity was increased when either of these herbicides was applied with either of the systemic insecticides phorate, O,O-diethyl S-(ethylthio) methyl phosphorodithioate or Di-syston, O,O,-diethyl S-[2-(ethylthio) ethyl] phosphorodithioate.

A metabolite of swep [methyl N-(3,4-dichlorophenyl)-carbamate] was detected in the straw, hulls and bran layer of rice but not in the polished rice grain (endosperm) or bran oil, using microcoulometric gas chromatography (MCGC). This metabolite was identified as a swep-lignin complex which is quite stable and not extractable from plant tissues by common organic solvents. Upon extraction with HCl-dioxane, a portion of this complex is hydrolyzed to swep and soluble products of lignin. The swep was purified by adsorption chromatography and identified by infrared spectroscopy and microcoulometric gas chromatography retention times. The mechanism of swep-lignin complex formation is considered to be an example of a common detoxification mechanism by plants through immobilization.

Movement of 2-methoxy-3,6-dichlorobenzoic acid (dicamba) and N,N-dimethyl-2,2-diphenylacetamide (diphenamid) in Hagerstown silty clay was greater with either 5 or 10 surface inches of water when the water was applied in 0.25-inch increments rather than 1-inch. Upward movement of these herbicides occurred under sub-irrigation and when surface-applied water was allowed to evaporate freely from the soil surface. Dicamba always moved more readily than diphenamid. The results indicate that weather patterns may be important in addition to total rainfall in determining the movement of herbicides in soil.

The toxicity of 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) and 2-chloro-4-ethylamino-6-isoproylamino-s-triazine (atrazine) to eight crops was determined. The crops in order of increasing tolerance to these herbicides were Southern Giant Curled mustard (Brassica juncea (L.) Coss.), Missouri 0-205 oats, Straight Eight cucumbers (Cucurbita sativa L.), Knox wheat, Clark soybeans, RS610 grain sorghum, GT-112 inbred corn, and F-6 inbred corn. Inactivation of simazine and atrazine applied at 2 lb/A on field plots, as determined by soybean and oat bioassay, was most rapid when the soil environment was favorable for the growth of microorganisms. Very little inactivation occurred between September, 1960, and June, 1961, following a May, 1960 application. One year after application, 0.16 lb/A of atrazine and 0.31 lb/A of simazine were detected, but neither was detected after 16 months.

In two experiments beans were kept weed-free for various periods early in the season, and in a third, weeds were allowed to grow with beans for various periods before being removed. Weeds which emerged soon after planting caused extensive reductions in bean yields, but the actual yield-reducing competition occurred considerably later in the season. For 5 to 7 weeks after planting, the grower must control weeds by chemical or other means; for the remainder of the season, bean competition provides weed control.

All horizontal underground structures were roots and not rhizomes. The small, light-colored feeder roots are short-lived and consist mainly of primary tissue. Only one transition zone per clone was found. This was found in the collet (lower hypocotylary swelling). The transition from exarch, radial stele of the root, to endarch, collateral stele of the upper collet, was complete in approximately 2500 microns. All root primordia examined had endogenous origin from pericycle and pericyclic tissues. Buds arose endogenously in roots but exogenously in the region of the hypocotyl with endarch protoxylem. Primordia were often identified as roots or shoots prior to their emergence from the main axis.

The alkanolamine salt of 2,4-dichlorophenoxyacetic acid (2,4-D), the dimethylamine salt of 2,3,6-trichlorobenzoic acid (2,3,6-TBA), and the sodium salt of 2,3,6-trichlorophenylacetic acid (fenac), were evaluated in controlling witchweed and toxicity to corn on germinating seed in petri dishes, as preplan ting, preemergence, and postemergence treatments in the greenhouse and as preplanting, soil-incorporated treatments in the field. Corn roots were affected more than the shoots by each herbicide. Fenac and 2,4-D inhibited root growth of corn seedlings in petri dishes more than 2,3,6-TBA. Fenac was the most effective herbicide for control of witchweed and weedy grasses when applied as a preplanting, soil-incorporated treatment and controlled witchweed at rates which significantly increased corn yields. Applied preplanting, 2,4-D did not control witchweed and 2,3,6-TBA at rates which gave witchweed control equivalent to that obtained with fenac was toxic to corn.

The postemergence herbicidal activity and specificity of 16 s-triazines on 8 test species were determined at 3 application rates and the influence of various substitutions discussed.

Sorghum grain yield losses in Northwest and Central Texas caused by uncontrolled weed growth varied from 8 to 41%. Under high moisture conditions, sorghum competed best with weeds when planted thickly in narrow rows. With less moisture, seeding in wide rows resulted in more effective competition. If rains produced weed germination immediately after planting, competition with the sorghum was more severe than when weeds germinated 1 or 2 months after sorghum planting. Several mechanical weed control methods were very successful.

The most promising of 13 herbicides for the control of southern naiad (Najas guadalupensis (Spreng.) Magnus) were acrylaldehyde (acrolein), mono-N,N-dimethylcocoamine and di-N,N-dimethylcocoamine salts of 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid (endothall), 6,7-dihydrodipyrido[1,2-a:2’,1′-c] pyrazidiinium salt (diquat), and 1,1′-dimethyl-4,4′-bypyridinium salt (paraquat). Acrolein and the 2 alkylamine salts of endothall gave the most rapid kill of southern naiad but retreatment was necessary at the end of 16 weeks. Diquat and paraquat were the 2 most promising materials evaluated. Large scale applications of acrolein, di-N,N-dimethylcocoamine salt of endothall and diquat confirmed these results. Diquat and paraquat were the only herbicides of the 13 that were not toxic to fish.

Volunteer wheat and downy brome (Bromus tectorum L.) were consistently controlled by aerial applications of granular 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) without supplemental tillage. Injury to winter wheat seeded in the fall 13 and 14 months after application of atrazine has occurred. Plots aerially treated with 2 lb/A atrazine produced yields comparable to the check but plots treated with 4 lb/A atrazine produced no wheat. Use of persistent herbicides for chemical fallow must be restricted until further knowledge is obtained.

Flat pea (Lathyrus sylvestris L.), previously investigated as a forage plant in the United States, is a perennial legume with undesirable qualities of low palatability, difficulty of establishment, and a toxic principle. Characteristically aggressive and tolerant to a wide range of growth conditions, it is a potentially serious weed in its area of adaptation. A related species, everlasting pea (L. latifolius L.), has similar characteristics. A 2-lb/A rate of 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), 2-(2,4,5-trichlorophenoxy)propionic acid (silvex), or 2,3,6-trichlorobenzoic acid (2,3,6-TBA) followed by 2-lb/A of silvex a year later gave complete control of established plants and seedlings of flat pea.

Experiments were conducted at Lincoln, North Platte, and Alliance, Nebraska, during 1961 and 1962 to determine the effect of tillage, atrazine, hand-weeding, and row spacings on RS 501 sorghum and weed yields. Combinations of tillage, narrow row spacings, and preemergence 2-chloro-4-ethylamino-6-isoproplyamino-s-triazine (atrazine) treatments gave more dependable weed control than any one alone. Sorghum yields increased and weed yields decreased with tillage and atrazine treatments. Preemergence atrazine applications as low as 1 lb/A gave higher sorghum yields and lower weed yields than postemergence atrazine applications of 2 to 4 lb/A. Preemergence atrazine applications should be reduced on lighter soils because atrazine gives more effective weed control and increased sorghum injury on such soils. There was a 1 bu/A decrease in sorghum yield for each 50 lb/A of weeds present.

Saltcedar (Tamarix pentandra Pall.) and Woods rose (Rosa woodsii Lindl. var. ultramontana [Wats.] Jeps.) were sprayed with systemic herbicides at frequent intervals over a 2-year period. Root samples were collected at each spray date and analyzed for “total available carbohydrates.” Food reserve levels in the roots and response to herbicides were not correlated.

2-chloro-4-isopropylamino-6-ethylamino-s-triazine (atrazine) applied at 3 lb/A to wheat stubble shortly after harvest in 1961 and 1962 controlled all vegetation for the remainder of the season. 2-chloro-4,6-bis(isopropylamino)-s-triazine (propazine) was nearly as effective as atrazine in 1962. Grain sorghum was planted in the spring of 1962. No preplanting tillage was used, and no weed control measures were needed in sorghum during the growing season on the treated plots, and crop stands, vigor, and grain yields were superior to those on the cultivated checks.

The adsorption of herbicides from aqueous solution by muck (organic soil), bentonite, an anion exchanger, and a cation exchanger was studied. The nature of the adsorbent, pH, and temperature all influenced adsorption, and different herbicides responded differently to changes in these factors. Lowering of the pH resulted in increased adsorption by bentonite of all of the herbicides studied, except 6,7-dihydrodipyrido (1,2-a: 2’, 1′-c) pyrazidiinium salt (diquat) which was completely adsorbed at both a high and a low pH. The influence of pH was greatest for 4,6-dinitro-o-sec-butylphenol (DNBP) and 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine). The DNBP was adsorbed by an anion exchanger, but not by a cation exchanger, while isopropyl N-(3-chlorophenyl)carbamate (CIPC), 3-(p-chlorophenyl)-1,1-dimethylurea (monuron), and atrazine were adsorbed by both. Diquat was completely adsorbed by the cation exchanger and only slightly by the anion exchanger. All were adsorbed by muck but to varying extents as follows: diquat > CIPC > DNBP > monuron > atrazine. No relationship was found between water solubility and adsorption. Adsorption by bentonite (pH 8.5) was much greater at 0C than at 50C, but adsorption by muck was the same at both temperatures.

Desorption studies were conducted using C14-labeled atrazine, monuron, 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine), 3-amino-2,5-dichlorobenzoic acid (amiben), and 2,4-dichlorophenoxyacetic acid (2,4-D). Repeated extractions with distilled water desorbed these herbicides from bentonite and muck and their desorption was more readily accomplished from bentonite than from muck.