Prior to planting of birdsfoot trefoil (Lotus corniculatus L.), stony soils were sprayed with ethyl N,N-dipropylthiocarbamate (EPTC) at 0, 2.0, or 4.0 lb/A and were tandem-disked or harrowed 0, 1, 2, or 3 times or rotary-tilled to incorporate the herbicide. Rotary tillage was the best incorporation method where stones were not numerous. Tandem disking was the most practical. Annual grasses were controlled by 2.0 lb/A EPTC and one incorporation. Higher rates of EPTC and more incorporations resulted in better annual broadleaf weed control and increased yields of birdsfoot trefoil.

The herbicides 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), and 2-methoxy-3,6-dichlorobenzoic acid (dicamba) each labeled in the carboxyl position were sprayed on a pasture consisting of a mixture of silver beardgrass (Andropogon saccharoides Swartz.), little bluestem (A. scoparius Michx.), and dallisgrass (Paspalum dilatatum Poir.) and a sideoats grama (Bouteloua curtipendula [Michx.] Torr.) pasture over a 3-year period. Plant samples were harvested at intervals between 1 hr and 16 weeks after treatment and residues determined by radioassay. No important differences were found in the persistence of herbicides or of different formulations of the same herbicide. Rainfall was the most important factor influencing the persistence of the herbicides. The little bluestem-silver beardgrass-dallisgrass samples harvested 1 hr after treatment with the butoxyethyl ester of 2,4,5-T contained both this ester and the acid of 2,4,5-T. One week after treatment, the acid of 2,4,5-T and unknown metabolites were found but no ester.

Plots planted to corn (Zea mays L. var. Mo. 880) were treated with 0, 2.5, 5, and 10 lb/A of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) or 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) plus 0, 100, or 200 lb/A of nitrogen fertilizer. Yields of corn forage harvested 5 weeks after planting were significantly reduced by herbicidal treatments. Reductions were more pronounced on corn treated with simazine than with atrazine. In a given year, yields of corn forage from each successive harvest were reduced less, percentagewise, than the previous ones. Yields of corn grain generally were unaffected by herbicidal treatments, except when 10 lb/A of simazine were applied. Herbicides caused an increase in percent nitrate in forage approximately 5 weeks after treatment. Percent of nitrogen in corn forage rose sharply, approximately 5 weeks after planting, due to herbicidal treatments, especially on plots not treated with nitrogen fertilizer.

Selected clones of field bindweed (Convolvulus arvensis L.) differing in susceptibility to foliage applications of 2,4-dichlorophenoxyacetic acid (2,4-D) were used in testing some of the various mechanisms proposed for the selective action of this chemical. The differences found in external morphology, such as degree of pubescence and number of stomata, showed no relationship to the selective action of 2,4-D. Entry of the chemical into the plant and translocation within the stem also were not critical factors.

The most pronounced physiological differences between resistant and susceptible clones of bindweed occurred at the cellular level. When incubated in a nutrient agar containing 2,4-D, excised stem sections of both clones produced callus tissue, but the callus of the susceptible clone, as compared to the resistant, was approximately double in volume, dry weight, and degree of hydration. With increasing age, stem sections of the susceptible clone became even more responsive to 2,4-D; the reverse was true for the resistant. The differential response of the two clones was less pronounced when 2,4-D was applied to the roots than when it was applied to the foliage.

Damping-off of pea (Pisum sativum) seedlings in autoclaved soil subsequently inoculated with Pythium debaryanum ATCC 9998 grown in potato dextrose broth in presence of 75 ppmw O-(2,4-dichlorophenyl) O-methyl isopropylphosphoramidothioate (DMPA) was not different than in soil inoculated with the fungus grown in potato dextrose broth without DMPA. Damping-off of pea seedlings was less in autoclaved soil subsequently inoculated with Pythium debaryanum ATCC 9998 and to which DMPA (100 ppmw) had been added than in inoculated soil with no DMPA present. Damping-off of pea seedlings germinated in soil from plots that had received annual applications of DMPA, 15 lb/A, was nearly as great as that in the control plots.

Effect of 3,5-dimethyltetrahydro-1,3,5,2H-thiadiazine-2-thione (DMTT) on the growth of Monterey pine (Pinus radiata) seedlings was studied at constant levels of soil moisture maintained by capillary fringes. A high content of water depressed the growth of plants but preserved their normal morphological balance. A low content of water produced succulent seedlings with inferior root systems. The results suggest that DMTT is better adapted to fine-textured soils with restricted aeration. Maintenance of water supply at field capacity of the soil also may improve the balance of nursery stock and its survival potential.

Growth of Oxalis cernua Thunb. was determined in different temperature regimes. Growth occurred in the 55 to 75 F range. Temperature variation promoted growth. Bulbs sprouted more rapidly and uniformly after storage at 35 F than after storage at 95 F. The weed probably is best adapted to areas with winter soil temperatures between 55 and 75 F.

A truck sprayer for applying herbicides to brush is described. It consists of a three-section, hydraulically controlled boom capable of spraying about a 22-ft swath on brush up to 12 ft tall. The spraying system is mounted on a ⅓-T truck equipped with additional lights for night spraying. Plots 22 ft wide by 50 to 200 ft long are sprayed.