Trifluralin Residues Research Articles

Weed Control in Double Cropped Corn, Grain Sorghum, or Soybeans Minimum‐Till Planted Following Canning Peas1

AbstractDouble cropping involving minimum‐till planting has become popular in many parts of the USA. In Wisconsin, double‐cropping usually includes canning peas (Pisum sativum L.) as the spring crop. Trifluralin (a,a,a‐trifluoro‐2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine) is used for weed control in much of this pea acreage. Since effects of trifluralin residues alone or in combination with subsequent herbicide treatments on summer crops and weeds were unknown, experiments were conducted at the Univ. of Wisconsin Arlington Farm in 1977 and 1978 on a Plano silt loam (Typic Argiudoll, fine, silty, mixed mesic) with 3.5 to 4.0% organic matter. Corn (Zea mays L.), grain sorghum (Sorghum bicolor L. Moench), and soybeans [Glycine max (L.) Merr.] were minimum‐till planted following canning peas grown with or without preplant‐incorporated trifluralin. Effects of two herbicide combinations and an untreated control were compared in each of the summer crops.Trifluralin controlled both broadleaf and grass weeds in canning peas but did not increase shelled pea yield. Average weed growth in corn, grain sorghum, and soybeans following peas treated with trifluralin was reduced 52, 52, and 62%, and average grain yields of corn and soybeans were increased 10 and 28%, respectively, compared with the same crops following untreated. peas. Trifluralin residues reduced grain sorghum stands (44%) and yields (17%).Alachlor [2‐chloro‐2′, 6′‐diethyl‐N‐(methoxymethyl) acetanilide] + atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine] + paraquat (1,1‐dimethyl‐4,4′‐bipyridinium ion) was more effective in reducing weed growth in minimum‐till corn than alachlor + cyanazine [2‐chloro‐4‐(1‐cyano‐1‐methylethylamino)‐6‐ethylamino‐s‐triazine] + paraquat. There was no significant difference between the two combinations in terms of corn grain yield, however. Alachlor + cyanazine + paraquat following trifluralin in peas resulted in better weed control in minimum‐till corn than a similar treatment applied to corn planted following peas grown without trifluralin. Atrazine + paraquat and 2,4‐D [(2,4‐dichlorophenoxy)acetic acid] + paraquat also provided excellent weed control in grain sorghum, and alachlor + linuron [3‐(3‐4‐dichlorophenyl)‐1‐methoy‐1‐methylurea] + paraquat, and linuron + paraquat provided excellent weed control and increased grain yields in soybeans when both crops were minimum‐till planted after peas treated with trifluralin. Overall, soybeans appeared to be the most successful of the three crops when minimum‐till double‐cropped following peas under southern Wisconsin conditions.

Influence of Herbicides and Tillage on Sweet Corn Double Cropped After Peas1

AbstractDinitroaniline herbicides are widely used for production of canning peas (Pisum sativum L.). These are residual herbicides and the effects of residues has been long recognized to be influenced by tillage. Careful evaluation of these compounds was thus needed before growers could consider growing sweet corn (Zea mays L.) following peas in a double cropping system. Peas were therefore established in a field study (Typic Argindoll finesilty, mixed mesic soil), using various dinitroaniline herbicides for weed control. After pea harvest, half the area was plowed and planted to sweet corn, and the remaining area was planted with a minimum tillage method to the same crop. Observations were made of weed growth and pea and sweet corn performance.The tillage and planting systems alone influenced both weeds and sweet corn. Giant foxtail (Seteria faberi Herrm.) and velvetleaf (Abutilon theophrasti Medic.) populations were 63 and 87% higher, respectively, in the sweet corn check plots planted with conventional tillage than when planted minimum till. Sweet com population and yield were 15.6 and 14.4% higher, respectively, with conventional tillage than with minimum tillage.The dinitroaniline herbicides had a significant impact on the sweet corn crop only when it was planted using the minimum till system. Dinitramine [N4,N4‐diethyl‐α,α,α‐trifluoro‐3,5‐dinitrotoluene‐2,4‐diamine], fluchloralin [N‐(2‐chloro‐ethyl)‐2,6‐dinitro‐N‐propyl‐4‐(trifluoro methyl)aniline], pendimethalin [N‐(l‐ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitrobenzenamine], trifluralin (α,α,α‐trifluoro‐2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine), and a combination of oryzalin [3,5‐dinitro‐N4, N4‐dipropyl‐sulfanilamide] plus trifluralin residues were effective in reducing giant foxtail and velvetleaf populations in sweet corn. Ethalfluralin [N‐l‐ethyl‐N‐(2‐methyl‐2‐propenyl)‐2,6‐dinitro‐4‐(trifluoromethyl)benzenamine] was effective in controlling the velvetleaf population. Trifluralin residues caused the greatest carryover injury to sweet corn stands and the intensity of injury increased with higher application rates. Only fluchloralin, ethalfluralin, and trifluralin at 0.84, 0.84, and 0.42 kg/ha, respectively, did not cause sweet corn injury. The best sweet corn yields were obtained following treatments of dinitramine, ethalfluralin, and fluchloralin.

AVAILABILITY OF THE HERBICIDE TRIFLURALIN FOR CONTROL OF WILD OATS AS INFLUENCED BY SOIL CHARACTERISTICS IN FOUR MANITOBA SOILS

The effects of soil properties on available phytotoxic residues and total extractable residues of the herbicide trifluralin were investigated in four Manitoba soils. The four soils, Red River heavy clay, Gladstone clay loam, Newdale loam, and Almasippi loamy sand, were treated with trifluralin at levels in the range 0.2–3.0 ppmw (dry weight soil), and the soils maintained at or near field capacity in the growth chamber. Available residues were determined at 0, 2, and 5 wk using a wild oat (Avena fatua) bioassay. Total residues were measured at regular intervals to 16 wk using ultrasonic extraction and gas–liquid chromatography analysis. Biological results showed that wild oat control expressed as ED50 required much less applied or residual trifluralin in Almasippi loamy sand than in Red River heavy clay, with the other two soils being intermediate. Total residues, on the other hand, remained highest in Red River heavy clay, although the differences between soil types were not great. Net loss of trifluralin was best explained by a first-order kinetic expression. Availability of phytotoxic residues was related mathematically to clay content of the soils in combination with time from application. It was further shown that bioassay is inadequate for determination of total residues in soils unless time from application is held constant.

FIELD PERSISTENCE AND MOVEMENT OF TRIFLURALIN IN TWO SOIL TYPES

Trifluralin (α, α, α-trifluoro-2, 4, dinitro-N, N-dipropyl-p-toluidine) was applied in 1973 to Egam loam and Beason clay field plots, which differed in slope and texture of the surface 12 in. of soil. Recommended (1×) and excessive (1.5× and 2×) rates of trifluralin were applied, and the herbicide was incorporated to a depth of 4 in. Movement of trifluralin below the 8-in. depth was essentially nil in both soils, but considerable movement occurred to the 8-in. depth in both. Trifluralin longevity in each soil was essentially the same, although higher rates were applied in the clay soil. On the average, less than 1% of the herbicide remained 5 months after application; an increasing trend of trifluralin residues with 1.5× and 2× rates was discerned, however. No herbicide was found in the soil the following spring (11 months after application). There was some evidence of upward movement of trifluralin in both soils. Trifluralin degradation followed first-order kinetics with half-life values of 35.8 and 25.7 days for Egam and Beason soils, respectively. Five weeks after herbicide application, control of two broad-leaf weeds and one grass weed was poor, being consistent with low herbicide concentrations (0.06 ppm) remaining in the soil at that time. The growth of oats (Avena sativa L.), a species sensitive to trifluralin, was also not significantly affected in the greenhouse at 0.05 ppm of trifluralin concentration.

Persistence of terbacil and trifluralin under different soil and climatic conditions

Summary:Soil samples were collected from forty‐three field trials conducted on ten soil types to investigate the residual activity of terbacil and trifluralin at the end of the cropping season, approximately 6 months after application. The soil was bioassayed in a glasshouse using soya beans and German millet for terbacil and trifluralin respectively. At 1 kg/ha terbacil phytotoxic residues occurred in a majority of the trials, while at 2 kg/ha such a carry‐over could be found in every case. Trifluralin doses of up to 1 kg/ha did not persist in toxic amounts in most soils, while application of 2 kg/ha showed residual activity in 74% of the trials and application of 4 kg/ha killed German millet in all instances. Results are also presented from the time‐rate dissipation studies conducted on both herbicides by assaying soil samples collected at monthly intervals.Both organic matter and clay content of the trial sites affected the persistence of terbacil, while trifluralin residues were influenced only by the soil organic matter content. Trial sites receiving high rainfall showed considerably less residues of terbacil, but the persistence of trifluralin was not affected by rainfall to any appreciable extent.

Determination of benefin and trifluralin residues by quantitative gas-liquid chromatography/mass spectrometry.

Determination of benefin and trifluralin residues by quantitative gas-liquid chromatography/mass spectrometry.

Movement and Persistence of Bensulide and Trifluralin in Irrigated Soil

Bensulide [0,0-diisopropyl phosphorodithioateS-ester withN-(2-mercaptoethyl)benzenesulfonamide] and trifluralin (α,α,α-trifluroro-2,6-dinitro-N,N-dipropyl-p-toluidine) were incorporated to a depth of 2.5 and 7.5 cm in sandy loam soil on the same plots in three annual applications to study the effect of incorporation depth on movement and persistence of the herbicides in furrow-irrigated soil. Bioassays and gas-liquid chromatographic assays indicated that, regardless of rainfall, both herbicides remained within the original soil zones of incorporation. Trifluralin persisted longer in soil as depth of incorporation was increased. Neither bensulide at 4.5 or 9.0 kg/ha nor trifluralin at 1.1 kg/ha persisted in appreciable amounts 12 months after treatment. At these rates, significant residues of bensulide and trifluralin were detected after 6 months only when tillage was restricted. Herbicide concentrations that persisted 6 months as determined in laboratory assays caused severe reduction in growth of field-grown sorghum [Sorghum bicolor(L.) Moench].

Nitralin and Trifluralin Persistence in Soil

Analysis of soil samples taken periodically from field plots on Dundee silty clay loam treated with single or dual annual applications of 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin) or α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) at 0.84 or 1.68 kg/ha indicated dissipation of the herbicides to a low residual level within 3 to 4 months following each application. No accumulation was noted with either herbicide regardless of frequency or rate of application. Nitralin phytotoxicity to sorghum (Sorghum bicolorL. ‘Dekalb 57E’) decreased more rapidly in soil that had received prior treatment with nitralin than in soil with no previous treatment. A microbiological influence is suggested because this effect was nullified by autoclaving the soil prior to herbicide treatment. This effect was not apparent with trifluralin. A survey of 250 fields indicated a significant, inverse correlation between nitralin and trifluralin residue level and soil pH. Nitralin persistence was greater in acid than in neutral soil.