Persistence Of Trifluralin Research Articles

Persistence of atrazine and trifluralin in a clay loam soil undergoing different temperature and moisture conditions.

Dissipation kinetics of atrazine and trifluralin in a clay loam soil was investigated in a laboratory incubation experiment under different temperature and moisture conditions. The soil was spiked with diluted atrazine and trifluralin concentrations at 4.50 and 4.25mg/kg soil, respectively, the moisture content adjusted to 40, 70, and 100% of field capacity (FC) and then incubated in three climatic chambers at 10, 20, and 30°C. For each of the herbicides, soil samples were collected at 0, 7, 21, 42, 70, and 105 days and analysed by Gas Chromatography-Electron Capture Detector (GC-ECD). A stochastic gamma model was used to model the dissipation of herbicides from the clay loam soil by incorporating environmental factors as covariates to determine half-life and days to complete dissipation. Results showed that temperature played a greater role on atrazine persistence than soil moisture; while the interaction effect of temperature and moisture was significant on the persistence of trifluralin over time. Atrazine dissipated more rapidly at 30°C compared to 10 and 20°C, with a half-life of 7.50 days and 326.23 days to reach complete dissipation. Rapid loss of trifluralin was observed at 70% moisture content when incubated at 30°C, with a half-life of 5.80 days and 182.01 days to complete dissipation. It was observed that the half-life of both herbicides tended to double with every 10°C decreases of temperature over the range tested. The model indicated that both atrazine and trifluralin have the potential to persist in clay loam soil for several years at temperature ≤20°C; which could potentially affect following crops in rotation.

Persistence of trifluralin in soil of oilseed rape fields in Western Greece

The persistence of trifluralin, a herbicide exhibiting persistent organic pollutant properties, was investigated in a clay loam (CL) type soil under conventional tillage of oilseed rape and in bare soil. Trifluralin residues were determined with high performance liquid chromatography (HPLC) with diode array detection (DAD) after extraction with acetonitrile using sonication. Trifluralin dissipation was followed for a time period of 150 days and it was characterised by a relative fast initial loss followed by slow dissipation. More rapid loss within the plots of conventional cultivation in comparison to bare soil was observed. The half-life of trifluralin calculated from first-order kinetics dissipation ranged from 53.3 to 56.8 days in the plots with oilseed rape while in bare soil it ranged from 67.9 to 71.4 days. One month after application a considerable loss of about 30% was observed in all fields. Two months later a loss of 40% was observed in bare soil and 60% in the plots cultivated with oilseed rape, indicating the role of crop in the dissipation of trifluralin. Sixteen to 23 per cent of the initial applied trifluralin still remained in soil 150 days after application.

Persistence and behavior of pesticides in cotton production in Turkish soils

Turkey is the sixth largest producer of cotton in the world. Two of the most commonly applied pesticides used in cotton production are trifluralin and endosulfan. Although both are very effective at controlling pests, their persistence in the environment poses risks to human health and the environment. Four loam soils and one silty-loam soil were studied to evaluate the persistence of trifluralin and endosulfan in relation to soil characteristics. Degradation with trifluralin reached as high as 70% of the applied doses. Soils with the highest organic matter content had the lowest degradation rate, indicating a tighter sorption of trifluralin. Endosulfan degradation was a function of soil type and the specific isomer, with beta-endosulfan depicting the highest degradation.

Fitotoxic effects of trifluralin to hybrid maize (zea mays l) and their persistance

The objective of the study was to analyze the susceptibility of three different types of hybrid maize to carryover potential of trifluralin using the bioassay, and persistence of trifluralin. Herbicide toxicity was analyzed by determining the inhibition of root and shoot length and fresh weight. In addition, using the bioassay trifluralin persistence in the leached chernozen soil type was studied applying two doses. Herbicide degradation was monitored over a period of one year following application during the two trial years. The hybrids tested showed a significant susceptibility to herbicide tested. The doses analyzed inhibited root length and fresh weight. Regression analysis was used to determine I50 values for the parameters tested thus proving fresh root weight reduction to be the most susceptible and accurately computed parameter. Hybrid ZPSC 633 was the most susceptible (with regard to the parameters tested). Higher herbicide doses provoked slower degradation of trifluralin, as confirmed by calculated DT-50 values. Trifluralin residues (applied at the rate of 960 g a.i.7ha) provoked no damage to ground parts. Root length and fresh weight inhibition was about 10% in the case of the most susceptible hybrid. However trifluralin (applied at the rate of 1920 g a.i./ha) residues one year following application provoked damage to ground parts (up to 20% in the case of the most susceptible hybrid), whereas root length and fresh weight inhibition was approx. 30%.

Tillage Effects on Persistence and Distribution of Trifluralin in Soil

AbstractThe aim of this study was to investigate the effects of the substitution of plowing with harrowing—twice in a 3‐yr crop rotation—on persistence and distribution of a persistent herbicide such as trifluralin (α,α,α‐trifluoro‐2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine) to rate these two tillage systems for their environmental impact (e.g., regarding potential ground water contamination with pesticides). Therefore, studies have been performed in Germany at two sites, a clayey silt in Reinshof and a loamy sand in Eickhorst. The herbicide was applied to oilseed rape (Brassica napus L. var. napus), followed in consecutive years by applications to wheat (Triticum aestivum L.) or to wheat followed by rye (Secale cereale L.). The disappearance time of 50% of the initial concentration (DT‐50 value) decreased from >300 d after preplant incorporation of trifluralin to <150 d after pre‐emergence treatment, losses being greater due to volatilization resulting from the lack of soil incorporation. No influence of different tillage systems on trifluralin persistence could be observed. Distribution of the herbicide in the top 30 cm of the soils, however, was significantly influenced by the soil cultivation systems. Reduced tillage (harrowing) in two consecutive years resulted in trifluralin concentrations in the soil layers 10 to 20 cm and 20 to 30 cm under the limit of determination (0.005 mg kg−1). In contrast, plowing led to trifluralin residues of up to 0.019 mg kg−1 in these soil layers. Although no trifluralin residues could be found in the 30‐ to 45‐cm and 45‐ to 60‐cm soil layers under either soil cultivation system, our results imply an increased risk of ground water contamination after plowing.

Degradation of trifluralin in three Victorian soils —long-term field trials

Summary. The persistence of trifluralin was investigated at 3 sites in southern Australia over 8 years. Persistence varied from year-to-year, with the highest persistence being recorded at all sites in the dry year of 1984. Trifluralin persistence (expressed as a percentage of the initial measured concentration) 1 year after application was lowest at Rutherglen (7–22%), followed by Dooen (7–26%) and Walpeup (13–120%). Trifluralin degradation at Walpeup in 1984 was negligible. The resultant high residue concentrations would have posed a threat to subsequent crops. However, 1 year later after the subsequent fallow, the residue concentration had dropped to more typical levels. Trifluralin did not accumulate after repeated application (either 1 or 2 years apart) at all 3 sites. It was found important to measure the amount of trifluralin in the soil immediately after application because the trifluralin concentration could not be assumed from the rate. Soil concentrations immediately after application ranged from 32 to 138% of that expected from the nominal application rate. Therefore, measuring initial concentrations when comparisons were to be made between treatments, years and sites, was essential. In addition to studies of 1 year persistence, trifluralin concentration was also measured 2 years after application at Walpeup and Dooen. There was evidence to suggest that the rate of degradation over the same 1 year period, was different for a recent application when compared with weathered trifluralin residues from a previous application. Correlations between persistence and various weather factors indicated that the most influential factors were those that occurred in the first 60 days after application. These included total rainfall, effective rainfall (rainfall minus evaporation) and average maximum temperature.

Environmental fate of trifluralin.

Trifluralin, a preemergence, soil-applied and soil-incorporated herbicide, has been in agricultural use since 1963. The environmental chemistry and fate of dinitroaniline herbicides, including trifluralin, has been studied extensively in agricultural soils. Probst et al. (1975) and Helling (1976) have summarized pre-1975 data on the mobility, persistence, and degradation or metabolism of dinitroaniline herbicides as a group. Since then, numerous studies have been carried out on the fate of dinitroanilines, especially trifluralin, in the environment to understand further their degradation in soil, potential for mobility and persistence, and environmental concentration in water and air. The present review, while summarizing briefly earlier data, concentrates primarily on the post-1975 data on degradation, mobility, and persistence of trifluralin in soils and its potential concentrations in water and air. Trifluralin is readily degraded under sunlight in all media, with half-lives (t1/2) of minutes to several months, depending on the substrate. In addition, other dissipation processes, such as microbial and chemical, are also operative in soils, water, and sediments. Several degradation products of trifluralin have been identified and characterized, both under photolysis and following aerobic and anaerobic metabolism in soils and water-sediment systems. The differences between various degradative pathways of trifluralin appear to be more quantitative than qualitative in nature, leading eventually to the same end products that are subject to binding or mineralization with time. The general lack of accumulation of the breakdown products of trifluralin suggests that these are also subject to the same degradative mechanisms as the parent compound. Trifluralin has low water solubility and is strongly bound to soil components; mean Koc values range from 4,000 to 13,000. Once applied and incorporated into the soil, trifluralin remains relatively immobile with minimal or no potential for contamination of groundwaters under or near the treated zones. Trifluralin residues in soil surface layers are subject to loss via transport in runoff water or volatilization into the air. Seasonal losses in surface runoff are consistently less than 0.5% of the amounts applied, with concentrations in edge-of-the-field run-off water typically < 1.0 microgram L-1. Consequently, trifluralin is infrequently detected in surface waters and, if present, usually occurs below levels of quantification. Seasonal trifluralin losses into the atmosphere can be as high as 25% of that applied. Maximum trifluralin residues in the air above treated fields are in the 2-3 micrograms m-3 range following application, decreasing to < 100 ng m-3 in ambient air of intensive use areas, indicating its rapid dissipation in air. Trifluralin residues at < 100 pg m-3 in the atmosphere of remote nonuse regions have been reported, suggesting its potential for long-range transport. However, there is a general lack of understanding of the mechanisms controlling its potential for long-distance transport, especially considering its rapid photodegradation in vapor and solution states. The persistence of trifluralin in agricultural soils following incorporation is highly variable, depending on several factors such as depth of incorporation, soil moisture, soil temperature, soil air, and soil organic matter content. Estimated half-lives under a variety of agronomic conditions range from 25 to > 201 d, thus categorizing its persistence from 'moderate' to 'persistent'. The estimated half-life data for trifluralin under agronomic conditions, however, cannot be extrapolated to other potential scenarios, such as its dissipation in nontarget areas where trifluralin residues, if any, are essentially deposited on surfaces. Surface deposits on nontarget areas, unlike soil-incorporated residues, would be subject to volatilization and photolysis and thus more short lived. (ABSTRACT TRUNCATED)

Carry-over of granular and emulsifiable concentrate formulations of trifluralin in Saskatchewan

The field persistence of trifluralin from fall treatments of both emulsifiable concentrate (EC) and granular formulations was investigated at two sites in Saskatchewan over a 2-yr period. At both locations, there were no significant differences (P = 0.05) in trifluralin persistence from fall applications of either formulation. In addition, the carryover of trifluralin residues in farmers’ fields following fall and spring applications of EC and granular formulations was monitored at several Saskatchewan locations to determine their persistence under typical farming practices. Trifluralin residue data indicated that following fall applications, the percent carry-over to the first spring was 83 ± 21(15 fields sampled) and 37 ± 15 (28 fields sampled) to the second spring; and that following spring applications, the percent carry-over to the next spring was 33 ± 12 (14 fields sampled). Key words: Field studies, persistence, formulations, trifluralin, herbicide

Degradation of trifluralin in three Victorian soils under field and laboratory conditions

The effects of soil moisture and temperature on trifluralin degradation were investigated in 3 Australian soils under field and laboratory conditions. For the field trials, the amount of trifluralin persisting over 1 year into the next cropping season varied from 9 to 24%. From laboratory experiments, separate relationships were derived for the effects of temperature and moisture 1 on trifluralin degradation. Trifluralin degradation I increased with both increasing moisture and increasing temperature. The results indicate potential for unusually long persistence of trifluralin in years of low rainfall when the soil becomes very dry. It is therefore recommended that analysis for trifluralin residues or activity be undertaken if a sensitive crop such as oat, sorghum, or millet, or a sensitive pasture species such as phalaris or ryegrass, is sown after very dry climatic conditions following trifluralin application. The wheatbelt regions of Australia do not experience cold conditions for long enough periods for low temperatures to be a major factor contributing to trifluralin persistence. Degradation was compared for trifluralin applied as a formulation of the herbicide and as the active ingredient alone, to determine the validity of results obtained using the pure herbicide. In half of the 6 field and laboratory studies, there was a statistically significant difference between degradation of trifluralin as the active ingredient and as the formulation. This indicates a need to use the formulated compound in laboratory experiments if results are to reflect normal agricultural practices.

The relative persistence of trifluralin (545 EC and 5 G) and ethalfluralin in prairie soils

The persistence in soil of trifluralin 545 EC, trifluralin 5 G, and ethalfluralin 360 EC was studied over a 2-yr period at three different sites in Saskatchewan. At two of the three sites both formulations of trifluralin were more persistent than ethalfluralin when a canola crop was grown in the treated soil. In the high organic matter soil at the third site the persistence of trifluralin and ethalfluralin was similar under both fallow and cropped conditions. Crop response data gathered from wheat, oat and millet stands plus gas chromatographic analysis of soil extracts indicated that trifluralin 545 EC and trifluralin 5 G persisted in soil for comparable lengths of time when applied at rates between 0.85 and 1.40 kg a.i. ha−1. At recommended application rates to summerfallowed fields, the amount of herbicide remaining in the different soils at seeding time the following season was least for ethalfluralin 360 EC. The average amount of trifluralin 545 EC, trifluralin 5 G and ethalfluralin 360 EC which remained in the soil at the three field locations the year following application was 13, 13 and 6%, respectively. Key words: Trifluralin, ethalfluralin, herbicide persistence

EFEITO DA TRIFLURALINA SOBRE A ATIVIDADE BIOLÓGICA EM DOIS SOLOS

A influência da Trifluralina 600 CE sobre a atividade microbiana e taxa de liberação de CO2 foi estudada com amostras de solos da Unidade de Mapeamento São Pedro e Cruz Alta, incubados a 80% da capacidade de campo ou saturados, com tratamentos equivalendo a 2 e 4 litros por hectare, com cinco repetições, durante 140 dias. A cada sete dias foram efetuadas titulações de CO2 liberado. Posteriormente foi executado bioensaio com Sorghum bicolor L. Moench para análise da persistência do produto no solo. O herbicida nas dosagens usadas não afetou a atividade microbiana. A persistência do herbicida mostrou diferença significativa entre plântulas anormais para os dois solos em capacidade de campo, o mesmo não ocorrendo quando a germinação foi em solos saturados.

Mathematical Description of Trifluralin Degradation in Soil

Degradation of trifluralin in four soils, each represented at four sites, under field conditions was determined quantitatively and described mathematically. A biexponential equation that resulted from integration of first-order and second-order differential rate equations described degradation data better than the first-order kinetic model for 15 of 25 soil-site combinations. Biexponential model regression coefficients indicated extent of degradation and that degradation is rapid at initially high trifluralin concentrations but slows as concentration decreases. The first-order kinetic model initially underestimated but ultimately overestimated degradation of trifluralin, thereby inferring that a first-order half-life is inadequate for predicting trifluralin persistence.

Trifluralin persistence under two different soil and climatic conditions

SummaryAn investigation of the persistence of trifluralin was conducted as field experiments over a two year period at latitudes 60°N and 70°N respectively, paying special attention to the soil and climatic conditions. These experiments included glasshouse bioassays with Lolium multiflorum. gas‐chromatographic residue analyses and qualitative and quantitative studies on soil bacteria. Special attention was devoted to clay minerals as well as to the soil organic matter. 100 g or 500 g of trifluralin a.i. ha−1 were applied in the spring 1978 with a reapplication on half of the area the following spring (1979).The phytotoxicity of trifluralin appeared more severe on re‐treated plots compared with single applications even at approximately equal residue levels. Trifluralin did not seem to have any real influence on the total number of soil bacteria. A qualitative change of the bacterial flora was however observed as a relative increase of non‐sporeformers, Gram negatives and Actinomy‐cetes and a relative depression of the Coryneform bacteria/Arthrobacter group.Even at a recommended dosage, a carry‐over phytotoxicity the following year may occur, especially when the content of organic matter in the soil is low. Care should therefore be taken when using this herbicide on the same field in two successive years. The properties of the soil seemed to exert a greater influence than the climatic factors on the persistence of trifluralin.

PERSISTENCE AND PHYTOTOXICITY OF DINITROANILINE HERBICIDES IN MANITOBA SOILS

The persistence and phytotoxicity of dinitramine (n4, N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine), fluchloralin (N-(2-chloroethyl)-2, 6-dinitro- N-propyl-4- (trifluoromethyl)aniline), profluralin (N-(cyclopropylmethyl)α,α,α-trifluoro-2, 6-dinitro-N-propyl-p-toluidine), and trifluralin (α,α,α-trifluoro-2,6-dinitro-N-N-dipropyl-p-toluidine) were compared in three Manitoba soils: sandy loam, clay loam and clay. The phytotoxicities of all chemicals decreased with increased organic matter. The phytotoxicities of the dinitroanilines were: dinitramine &gt; trifluralin &gt; profluralin = fluchloralin. Increased organic matter increased the persistence of trifluralin and fluchloralin. Profluralin and dinitramine persistence increased with increased clay and organic matter content. Profluralin was the most persistent chemical over all soil types. Under environmental conditions that retard dinitroaniline loss from Manitoba soils, residues of some of these herbicides may cause crop injury the year after application.

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.

Soil Persistence of Trifluralin, Benefin, and Nitralin

Trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline], and benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine) were applied at two rates for five consecutive years (1966 through 1970) as soil-incorporated treatments to cotton (Gossypium hirsutumL. ‘Acala SJ-1’) before the preplanting irrigation. Repeated applications did not significantly affect stand or yield of cotton. Soil samples taken to depth of 120 cm showed that herbicide residues were confined to the tilled zone of soil (upper 30 cm), and about 80% of the residue was in the upper 15 cm of soil. The amount of herbicide residue found annually in the upper 15 cm of soil varied with herbicide and with season. Residues 15 months after final application had been reduced markedly, but were still sufficient to injure sensitive crops. Residues at 30 months had been reduced to innocuous amounts.

Behaviour and persistence of trifluralin in soil

Summary: Résumé: ZusammenfassungThe growth response of sorghum to trifluralin, on various soils and soil mixtures, was significantly correlated with organic matter (ranging from &lt;0–1% to 20–4%) but not with clay content (ranging from 3% to 63%). However, in soils with a similar, low organic matter content, the activity of trifluralin increased with increasing clay content. No correlation was found between phytotoxicity of trifluralin and lime content of soils.The persistence of trifluralin incorporated in soil was examined by repeated reseedings of sorghum. Phytotoxicity lasted longer in soil dried and mixed at each interval between seedings than in soil left undisturbed; after 2 months about 50% of the original 4 ppm trifluralin remained in undisturbed soil vs 60 % in repeatedly mixed soil. The rate of degradation, after 2 months of incubation at 50% field capacity, increased with temperatures from 10°to40° the concentration of trifluralin required for a given growth reduction was approximately eight times greater after incubation at 40° than at 10°C.Comportement et persistattce de la trifluraline dans le solLes effets de Ia trifluraline sur la croissance du sorgho cultivé dans divers sols ou mélanges de sol se sont révlés être en corrélation significative avec la matiere organique (entre &lt; 0,1 % et 20,4 %) mais pas avec la teneur en argile (de 3 % A 63 %). Toutefois dans les sols contenant un taux analogue et faible de matiére organique, l'activité de la trifluraline s'est accrue en même temps que Ia leneur en argile. Aucune corrélation n'a été constatée entre la phytotoxicité de la trifluraline et la teneur en calcaire des sols.La persistance de la trifluraline incorporée dans le sol a été examinée au moyen de ressemis répétés de sorgho. La phytotoxicité dura plus longtemps dans le sol séché et remuéà chaque intervalle entre les semis que dans le sol non travaillé; au bout de 2 mois, 50% environ des 4 ppm de trifluraline apportés à. I'origine restaient dans le sol non remué contre 60% dans le sol plusieurs fois remué. Le taux de degradation, aprés deux mois d'inciibation à 50% de la capacityé au champ, augmenta avec la température de 10°à 40°C; la concentration de trifturaline nécessaire pour obtenir une réduction de croissance donnée fut approximativement huit fois plus grande aprés incubation. à 40° qu'aprés incubation à 10°C. Verhalten und Perststenz von Trifluralin im Boden Die Wachstumsreaktion von Hirse gegenubcr Trifluralin in verschiedenen Böden und Bodenmischungen war signifikant mit dem Gehalt an organischer Substanz (&lt;0–1 %–20–4%) korreliert, nicht aber mit dem Tongehalt (von 3%‐63%). Jedoch nahm in Böden mit annähernd gleich niedrigen Gehalten an organischer Substanz die Wirksamkeit von Trifluralin mit steigendeni Tongehalt zu. Zwischen der Phytotoxizität von Trifluralin und dem Kalkgehalt der Böden wurde keine Korrelation gefunden.Die Persistenz von in den Boden eingearbeitetem Trifluralin wurde durch wiederholte Einsaat von Hirse untersucht. Die Phytotoxizität dauerte im Boden, der jeweils zwischen den Einsaaten getrocknet und gemischt worden war, langer an als im nicht derartig behandelten Boden. Nach 2 Monaten waren im letzteren Boden ungefähr 50% der ursprüinglichen 4 ppm Trifluralin verblicben gegenüber 60% im wiederholt durchmischten Boden. Nach 2 Monatlen Inkubation bei 50% Feldkapazität stieg die Abbaurate, wenn die Temperatur von 10° auf 40°C stieg; die für eine gegebene Wachstumsreduktion benötigte Trifluralinkonzentration war bei 40° annShernd achtfach grösser als bei 10°C.

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.

Persistence of trifluralin in small field plots as analyzed by a rapid gas chromatographic method

Persistence of trifluralin in small field plots as analyzed by a rapid gas chromatographic method

Effect of Soil Incorporation on Selectivity, Movement, and Persistence of Herbicides in Watermelon Plantings1

Abstract A combination treatment of preemergence O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide (bensulide) at 5 kg/ha plus postemergence a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) at 0.6 kg/ha gave outstanding weed control when applications were incorporated 2.5 cm in soil. The treatment controlled redroot pigweed (Amaranthus retroflexus L.) and barnyardgrass [Echinochloa crusgalli (L.) Beauv.] without reducing the yield of ‘Charleston Grey’ watermelon (Citrullus vulgaris Schrad.). High rates of application of bensulide alone reduced yields. Isopropalin (2,6-dinitro-N,N-dipropylcumidine) and methyl-(4-amino-benzene)sulfonyl carbamate (MB-9057) were promising, but N-butyl-N-ethyl-a,a,a-trifluoro-2, 6-dinitro-p-toluidine (benefin), 2-chloroallyl diethyldithiocarbamate (CDEC), dimethyl tetrachloroterephthalate (DCPA), and 4-(methylsulfonyl)-2, 6-dinitro-N,N-dipropylaniline (nitralin) were less effective. Several herbicides controlled weeds more efficiently when soil-incorporated 5.0 cm rather than 1.3 cm. Deep incorporation of preemergence applications of benefin and trifluralin reduced the yields. Oversprays of a petroleum mulch had no effect on preemergence applications of bensulide but increased soil temp, soil moisture, and crop yields. Laboratory bioassays showed that under high temp, furrow irrigation, and low rainfall, trifluralin moved upwards in sandy clay loam and had a half-life of 1 and 3 weeks with 1.3- and 5.0-cm incorporation in soil, respectively. Persistence of trifluralin increased with rate of application and depth of incorporation. Traces of trifluralin activity were found 5 months after treatment only with the 1.1 kg/ha application soil-incorporated 5.0 cm. Field bioassays showed that whereas bensulide, benefin, and trifluralin reduced the growth of German millet [Setaria italica (L.) Beauv.], only bensulide reduced the growth of sorghum (Sorghum vulgare L.). Crop injury increased with rate of application and depth of incorporation.