Handweeding sugarbeets (Beta vulgaris L. ‘Mono Hy D2’) for 8 weeks after planting prevented sugarbeet yield losses. Weeds invading sugarbeet plots at the two-leaf stage (4 weeks after planting) reduced sugarbeet yields 26%. Cycloate (S-ethyl N-ethylthiocyclohexanecarbamate) caused more visual sugarbeet injury and stand reduction than did ethofumesate [(±)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate]. Broadleaf and grass weeds differed in their response to cycloate and ethofumesate, but overall, total weed yields were lower in plots treated with cycloate. Ethofumesate injured sugarbeets more when applied before planting and incorporated into the soil than when applied preemergence. Herbicides applied when sugarbeets had four to six leaves generally injured sugarbeets less, but controlled weeds less effectively, than when sugarbeets had two to four leaves. None of these herbicide treatments were as effective as handweeding in providing season-long weed control. Every 1120 kg/ha of oven dry weeds present in sugarbeet fields corresponded to a decrease in sugarbeet root yields of 10 000 to 11 500 kg/ha.

Metribuzin [4-ammo-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] at 0.4 kg ai/ha controlled rape (Brassica hitra Moench. # SINAL) when applied 2.5 to 10 cm deep in a horizontal layer or in lines 1 to 4 cm apart. Trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 0.8 kg ai/ha did not control ‘Rox Orange’ forage sorghum [Sorghum bicolor (L.) Moench. # SORVU] satisfactorily when applied in a subsurface layer, in lines, or in vertical bands 1, 2, and 3 cm apart up to 10 cm deep. Applications of trifluralin at 1.1 kg ai/ha in vertical bands followed by 0.6 kg ai/ha mixed in the surface 2.5 cm controlled forage sorghum as well as or better than surface application followed by incorporation. The combined subsurface and surface trifluralin placement systems were effective for application depths up to 7.5 cm and band spacings up to 2 cm wide. The development of effective subsurface herbicide injection systems would make the use of herbicides requiring incorporation feasible in reduced tillage crop production systems.

In field studies conducted in 1971 through 1977 weed yields were higher in EPTC (S-ethyl dipropylthiocarbamate) and alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide]-treated areas as compared to handweeded plots. Weeds present in EPTC-and alachlortreated areas did not result in a significant field bean (Phaseolus vulgaris L. ‘Great Northern 59’) yield reduction as compared to hand-weeded plots. For every 1000 kg of dry weeds present in field beans there was a corresponding decrease in field bean yields of 208 kg/ha. Weed yields produced in plots treated with alachlor, dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine), EPTC, metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), and profluralin [N-(cyclopropylmethyl)-α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine] were significantly less when herbicides were incorporated with the rotary tiller as compared to incorporation with the spike-tooth harrow. Incorporation method was not as critical with butralin [4-(1,1-dimethylethyl)-N-(1-methylpropyl)-2,6-dinitrobenzenamine], with spike-tooth harrow incorporation of herbicides providing similar weed control to that obtained with the rotary tiller. Weed densities and yields were higher in plots seeded with field bean determinate variety ‘Great Northern 1140’ than in plots seeded with indeterminate variety ‘Tara’, when either EPTC or alachlor were applied preplant and incorporated. Neither field bean variety competed well with weeds when no herbicide was used.

Field studies were conducted in 1978 and 1979 on broadleaf signalgrass [Brachiaria platyphylla (Griseb.) Nash] management in peanuts [Arachis hypogaea (L.) ‘Florigiant′]. In both years, preplant incorporated applications of benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine), alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] provided better than 75% initial control of broadleaf signalgrass. Preemergence applications of alachlor and metolachlor provided 90% or better initial control. Vernolate (S-propyl dipropylthiocarbamate) and diphenamid (N,N-dimethyl-2,2-diphenylacetamide) provided less than 45% initial control. An at-cracking application of dinoseb (2-sec-butyl-4,6-dinitrophenol) plus naptalam (N-1-naphthylphthalamic acid) plus either alachlor or metolachlor increased control over that provided by at-planting herbicides alone and maximum yields were obtained. No at-planting herbicide alone provided better than 60% control at harvest and consequently yields were lower. In three of four experiments, sequential applications of at-planting and at-cracking herbicides provided better than 75% control at harvest. In the fourth experiment, only benefin and metolachlor followed by at-cracking applications provided better than 70% control at harvest.

The influence of several environmental and edaphic factors on alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] selectivity in snap bean (Phaseolus vulgaris L.) was examined. Crop safety was consistently improved when alachlor was applied preplant incorporated as compared to surface preemergence treatment. Under field conditions, maximum injury occurred either when temperatures during germination were cool and rainfall was minimal, or when temperatures approached or exceeded 27 C and the soil was saturated. In the growth chamber, more damage occurred under low temperature regimes, although volatilization of alachlor from moist soil also produced injury under higher temperatures. Injury was less severe in soils high in organic matter content. Alachlor injury decreased after 5 cm of simulated rainfall were applied on a loamy sand.

Experiments were conducted in the greenhouse and in the field to determine the influence of flax (Linum usitatissimum L.) seeding depth on tolerance to trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine]. Flax stand and fresh weight generally decreased as flax seeding depth increased within or below trifluralin-treated soil. Seeding flax below a trifluralin-treated soil layer did not increase tolerance to trifluralin. Although 0.8 kg ai/ha of trifluralin reduced stand when flax was seeded 3 to 6 cm deep in the field, seed yield remained constant.

Woolly cupgrass control with acetochlor, alachlor, and metolachlor in corn was evaluated at Stratford, IA from 1985 through 1990. Averaged over application techniques, acetochlor at 3.4 kg/ha controlled more than 85% of woolly cupgrass five out of six years, whereas alachlor at 4.5 kg/ha and metolachlor at 3.4 kg/ha controlled more than 85% of this weed one and two years out of six, respectively. Herbicide incorporation did not consistently improve woolly cupgrass control. PRE applications were more effective than incorporated treatments in years with greater than 7 mm rainfall occurring within 3 d after application.

A 4-yr study (1985, 1987, 1988, 1989) was conducted on the same field plots at Shafter, CA to evaluate the efficacy of prometryn in controlling black nightshade on planting beds of cotton. Two rates (1.7 and 2.2 kg ai ha–1) were applied at two times (mid March before the preplant irrigation and early April at cotton planting) each year. Incorporation of prometryn into moist planting beds with a powered rotary tiller operated at 10 cm deeper resulted in excellent control of black nightshade under low to moderate weed pressure in 1985 and 1987. Control of nightshade with early and late applications of 1.7 kg ha–1 of prometryn under high weed pressure in 1988 was only 70% at harvest, and yield losses of cotton averaged 25%. Yields of cotton treated with 2.2 kg ha–1 of prometryn in 1988 were not significantly different from weed-free plots. Only the late application of 2.2 kg ha–1 of prometryn prevented significant cotton losses under extreme weed pressure in 1989. Cotton yield losses with the other prometryn treatments ranged from 78 to 100%. Losses of cotton in weedy-check plots that received only cultivation ranged from 22% in the absence of rain or irrigation at cotton planting in 1987 to as much as 100% when rain fell in 1988 or plots were irrigated at planting in 1989. Plots hoed one time 4 wk after cotton planting yielded an average of 84% as much seed cotton as weed-free plots. In an attempt to determine why the efficacy of prometryn declined between 1985 and 1989, several experiments were conducted in 1988 to 1990 to discover reasons for this poor control of nightshade. Because efforts failed to provide evidence for the movement of the herbicide with water, the development of weed resistance to prometryn, or accelerated degradation of this herbicide in soil, increasing weed seed populations in soil were believed to have contributed greatly to the declining nightshade control from prometryn. The fact that prometryn applied and incorporated into flat soil provided excellent control of nightshade in 1990 under sprinkler irrigation indicated that both soil moisture and incorporation techniques limited activity of prometryn in planting beds in 1988 and 1989. Incomplete control of nightshade plus good soil moisture at planting contributed to the high weed populations in 1988 and 1989.

The methyl ester of diclofop {2-[4-(2,4-dichlorophenoxy)phenoxy] propanoic acid} applied at 0.8 to 1.4 kg ai/ha and incorporated prior to seeding winter wheat (Triticum aestivum L.) controlled downy brome (Bromus tectorum L. ♯ BROTE) better than when applied preemergence at 1.7 kg/ha in 2 of 4 yr. The emulsifiable concentrate and a granular formulation of diclofop performed similarly. Controlling downy brome improved wheat yields 3 of 4 yr. However, preplant-incorporated applications of diclofop at 1.4 kg/ha reduced wheat yield 1 of 4 yr. Greenhouse data indicated that diclofop dissipated more rapidly in moist soil than in air-dry soil.