Clomazone Treatments Research Articles

Pre-and post-emergence herbicide selectivity in peanuts at an early stage

Studies on herbicide selectivity to peanuts detected differences according to the evaluated active ingredient and genotypes. This study analyzed the herbicide selectivity of two genotypes at an early stage. Pre-emergence (trifluralin, pendimethalin, diclosulam, s-metolachlor, imazethapyr + flumioxazin, clomazone, sulfentrazone, and imazapic) and post-emergence (imazapic, bentazon, bentazon + imazamox, clethodim, quizalofop-p-ethyl, cloransulam-methyl, s-metolachlor, lactofen, 2,4-D, and carfentrazone) applications were assessed in 1253 OL and 2133 OL breeding lines. The effects of pre- (PRE) and post-emergence (POST) herbicides were the same for both genotypes, with PRE not affecting seedling emergence and shoot and root dry mass. Diclosulam was among the most selective PRE herbicides, while the clomazone treatment caused only mild damage. All tested POST herbicides caused damage for up to 14 days after application (DAA). At 28 DAA, most herbicides exhibited the same damage as the untreated control. Lactofen caused mild damage (11.8%) without reducing plant height and shoot and root dry mass. Diclosulam, clomazone, and lactofen are unregistered for peanut crops in Brazil, and further studies should test their selectivity for peanut cultivars. Screening studies on selectivity to imazapic, 2,4-D, and carfentrazone are also relevant to identifying sources of tolerance in peanut germplasm.

Effect of Different Herbicides on Development and Productivity of Sweet White Lupine (Lupinus albus L.)

White lupine (Lupinus albus L.) is a well-known green manure crop in Hungary, but the production of seeds can be badly impacted by weeds. The sweet white lupine ‘Nelly’ was grown on acidic sandy soil, and experimental plots were treated with different herbicides. Flumioxazin (0.06 kg ha−1), pendimethalin (5 L ha−1), dimethenamid-P (1.4 L ha−1), pethoxamid (2 L ha−1), clomazone (0.2 L ha−1), metobromuron (3 L ha−1), and metribuzin (0.55 L ha−1) were applied pre-emergence (1–2 days after sowing). Imazamox was also tested and applied post-emergence (1 L ha−1) when some basal leaves were clearly distinct (BBCH 2.3). In this paper, the weed control efficiency and the phytotoxicity of herbicides applied to lupine are examined. Vegetation index datasets were collected 12 times using a manual device and 2 times using an unmanned aerial vehicle (UAV). The phytotoxicity caused by herbicides was visually assessed on several occasions throughout the breeding season. The frequency of weed occurrence per treatment was assessed. The harvested seed yields, in kg ha−1, were analyzed after the seeds were cleaned. The herbicides metribuzin and imazamox caused extensive damage to white lupine. While pendimethalin, dimethenamid-P, pethoxamid, and clomazone were outstanding in several measured indicators, the final ranking which summarizes all the variables showed that only the pethoxamid and clomazone treatments performed better than the control. Metribuzin and imazamox were highly phytotoxic to white lupine. In the future, it would be appropriate to integrate more post-emergence active substances into trials, and the pre-emergence herbicides involved in this study should be further tested.

Impact of clomazone on bacterial communities in two soils.

Bacterial communities are important for soil functions, but the effect of clomazone on network complexity, composition, and stability is not well studied. In this study, two agricultural soils were used to test the impact of clomazone on bacterial communities, and the two soils were treated with three concentrations of clomazone (0, 0.8, 8, and 80 mg kg1) in an incubator. Bacterial network nodes, links, and average degrees were all decreased by 9-384, 648-829, and 0.703-2.429, respectively. Based on keystone nodes, the topological roles of the nodes were also influenced by clomazone. Bacterial network composition was also impacted based on the analysis of similarity (ANOSIM) and network dissimilarity. Compared with control and clomazone treatments in both soils, the ANOSIM between control and all clomazone treatments was higher than 0.6, network dissimilarities were 0.97-0.98, shared nodes were 131-260, and shared links were 12-100. The bacterial network stability was decreased by clomazone, with decreased robustness by 0.01-0.016 and increased vulnerability by 0.00023-0.00147 in both soils. There were fewer bacterial network modules preserved after clomazone treatment, and the bacterial network community functions were also impacted in both soils. Based on these results, soil bacterial species connections, modularization, and network stability were significantly impacted by clomazone.

Clomazone impact on fungal network complexity and stability.

Soil fungal network composition and stability are important for soil functions, but there is less understanding of the impact of clomazone on network complexity and stability. In this work, two agricultural soils were used to investigate the impact of clomazone on fungal network complexity, composition, and stability. The two soils were treated with clomazone solution (0, 0.8, 8, and 80 mg kg-1) and kept in an incubator. Under the influence of clomazone, the fungal network nodes were decreased by 12-42; however, the average degree was increased by 0.169-1.468 and fungal network density was increased by 0.003-0.054. The keystone nodes were significantly changed after clomazone treatment. Network composition was also impacted. Specifically, compared with control and clomazone treatments in both soils, the shared edges were fewer than 54 in all comparisons, and network dissimilarity was 0.97-0.98. These results suggested that fungal network composition was significantly impacted. The network robustness was increased by 0.0018-0.0209, and vulnerability was decreased by 0.00018-0.00059 in both soils, which indicated that fungal network stability was increased by clomazone. In addition, the functions of network communities were also changed in both soils. These results indicated that clomazone could significantly impact soil fungal networks.

Pretreatment with alternation of light/dark periods improves the tolerance of tobacco (Nicotiana tabacum) to clomazone herbicide

This work analyses the effects of alternation of light/dark periods pretreatment (AL) in tobacco plantlets (Nicotiana tabacum L. cv.Virginie vk51) growing in solution with low concentration of the clomazone herbicide. The experimentation has been carried out by exposing the plantlets to successive and regulated periods of light (16min light/8min dark cycles, PAR 50μmolm−2s−1) for three days. The photosynthesis efficiency was determined by mean of the chlorophyll fluorescence and JIP-test. The AL pretreatment improved the clomazone tolerance; this has been observed by the increase in the leaf area of the plant, the maximal photochemical quantum efficiency of PSII (Fv/Fm), the actual PSII efficiency (ФPSII), the performance index (PIabs), the electron flux beyond Quinone A (1−VJ), and also by the diminution of the energy dissipating into heat (DI0/RC). Furthermore, AL pretreatment led to low accumulation of hydrogen peroxide (H2O2) which proves that the scavenging enzymatic system have been activated before clomazone treatment. In the plantlets pretreated with AL, with regard to the ascorbate content, some of antioxidant enzyme whose function is associated with it have continued to scavenge reactive oxygen species (ROS) induced by clomazone, such as ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR). So, the observed photooxidative damages induced by clomazone herbicide were noticeably reduced.

Effects of lovastatin, clomazone and methyl jasmonate treatment on the accumulation of purpurin and mollugin in cell suspension cultures of Rubia cordifolia

AimTo determine the IPP origin of the naphthoquinones (NQs) in Rubia cordifolia, and to evaluate the effects of methyl jasmonate (MeJA) treatment, MEP, and MVA pathway inhibitor treatment on the accumulation of anthraquinones (AQs) and NQs in cell suspension cultures of R. cordifolia. MethodsCell suspension cultures of R. cordifolia were established. Specific inhibitors (lovastatin and clomazone) and MeJA were supplied to the media, respectively. Treated cells were sampled every three days. Content determination of purpurin (AQs) and mollugin (NQs) were carried out using RP-HPLC. The yield of the two compounds was compared with the DMSO-supplied group and the possible mechanism was discussed. ResultsLovastatin treatment increased the yield of purpurin and mollugin significantly. Clomazone treatment resulted in a remarkable decrease of both compounds. In the MeJA-treated cells, the purpurin yield increased, meanwhile, the mollugin yield decreased compared with control. ConclusionThe IPP origin of mollugin in R. cordifolia cell suspension cultures was likely from the MEP pathway. To explain the different effects of MeJA on AQs and NQs accumulation, studies on the regulation and expression of the genes, especially after prenylation of 1,4-dihydroxy-2-naphthoic acid should be conducted.

Enzyme Inhibitor Studies Reveal Complex Control of Methyl-D-Erythritol 4-Phosphate (MEP) Pathway Enzyme Expression in Catharanthus roseus

In Catharanthus roseus, the monoterpene moiety exerts a strong flux control for monoterpene indole alkaloid (MIA) formation. Monoterpene synthesis depends on the methyl-D-erythritol 4-phosphate (MEP) pathway. Here, we have explored the regulation of this pathway in response to developmental and environmental cues and in response to specific enzyme inhibitors. For the MEP pathway entry enzyme 1-deoxy-D-xylulose 5-phosphate synthase (DXS), a new (type I) DXS isoform, CrDXS1, has been cloned, which, in contrast to previous reports on type II CrDXS, was not transcriptionally activated by the transcription factor ORCA3. Regulation of the MEP pathway in response to metabolic perturbations has been explored using the enzyme inhibitors clomazone (precursor of 5-ketochlomazone, inhibitor of DXS) and fosmidomycin (inhibitor of deoxyxylulose 5-phosphate reductoisomerase (DXR)), respectively. Young leaves of non-flowering plants were exposed to both inhibitors, adopting a non-invasive in vivo technique. Transcripts and proteins of DXS (3 isoforms), DXR, and hydroxymethylbutenyl diphosphate synthase (HDS) were monitored, and protein stability was followed in isolated chloroplasts. Transcripts for DXS1 were repressed by both inhibitors, whereas transcripts for DXS2A&B, DXR and HDS increased after clomazone treatment but were barely affected by fosmidomycin treatment. DXS protein accumulated in response to both inhibitors, whereas DXR and HDS proteins were less affected. Fosmidomycin-induced accumulation of DXS protein indicated substantial posttranscriptional regulation. Furthermore, fosmidomycin effectively protected DXR against degradation in planta and in isolated chloroplasts. Thus our results suggest that DXR protein stability may be affected by substrate binding. In summary, the present results provide novel insight into the regulation of DXS expression in C. roseus in response to MEP-pathway perturbation.

Controle químico de arroz-vermelho na cultura do arroz irrigado

A ocorrência de arroz-vermelho (Oryza spp.) em áreas de arroz irrigado reduz a produtividade de grãos da lavoura e a qualidade do produto colhido. Em vista disso, desenvolveu-se um experimento com o objetivo de comparar duas ferramentas para controle do arroz-vermelho: uma usando o Sistema Clearfield e outra utilizando doses elevadas de clomazone em sementes tratadas com protetor para supressão de arroz-vermelho. Os tratamentos constituíram-se de uma testemunha, sem aplicação de herbicida, três referentes à aplicação da mistura formulada (75 g i.a. ha L-1 de imazethapyr + 25 g i.a. ha L-1 de imazapic) e outros três referentes à aplicação do herbicida clomazone. O tratamento mais eficiente no controle de arroz-vermelho foi a aplicação da mistura formulada de imazethapyr + imazapic em pré-emergência, seguido da mesma dose em pós-emergência. Este tratamento proporcionou 100% de controle de arroz-vermelho, além de não prejudicar o estande inicial de plantas e proporcionar alto rendimento de grãos do arroz irrigado.

Control de malezas en arroz de temporal con clomazone, propanil y 2,4-D.

Between 1996 and 1997, three experiments were carried out in order to evaluate the effect of the herbicide clomazone, alone and mixed with propanil and 2,4-D on weed control and toxicity to rice cv. Milagro Filipino, growing under upland conditions. All the experiments were established in Los Naranjos, in the Municipality of Tres Valles, in the state of Veracruz. The dominant weed species in the experimental plots were Cyperus iria, Echinochloa colona, Cyperus rotundus, Scleria setuloso-ciliata and Malachra fasciata. Clomazone applied preemergent, efficiently controlled E. colona at 0.72 and 0.96 kg a. i./ha, but its effect was partial and temporary on S. setuloso-ciliata and it had no effect on C. iria and C. rotundus. The mixture of clomazone + propanil + 2,4-D efficiently controlled E. colona and C. iria from 0.60 + 1.44 + 0.24 kg a. i./ha and had a good initial control of C. rotundus, but its effect disappeared 45 to 60 days after the application. Rice yields obtained from clomazone treatments, alone or mixed with propanil and 2,4-D were statistically similar to those of the regional controls.

Bensulfuron and Halosulfuron Alter Clomazone Activity on Rice (Oryza sativa)

A laboratory study was conducted in 2003 at Louisiana State University in Baton Rouge, LA, to evaluate the interactive effects of bensulfuron or halosulfuron on clomazone in terms of rice foliar bleaching and chlorophyll content. Clomazone was applied alone at 0 and 1.227 μg/ml (672 g/ha) or in combination with bensulfuron at 0.0276 μg ai/ml (42 g ai/ha) or halosulfuron at 0.0345 μg ai/ml (53 g ai/ha) in a hydroponic solution. Bensulfuron and halosulfuron were also applied alone. Rice cultivars evaluated included short-grain ‘Pirogue’, medium-grain ‘Bengal’, and long-grain ‘Cocodrie’. Bensulfuron and halosulfuron, applied in a hydroponic solution, safened medium-grain Bengal, long-grain Cocodrie, and short-grain Pirogue at 21 d after treatment (DAT) from foliar bleaching caused by clomazone. Chlorophyllaandband total chlorophyll content of all three rice cultivars decreased when treated with clomazone treatment. Only chlorophyll content of Cocodrie was increased by the addition of bensulfuron and halosulfuron compared with a single application of clomazone.

The basis for the safening of clomazone by phorate insecticide in cotton and inhibitors of cytochrome P450s

Clomazone may be safely used in cotton to manage weeds when applied following treatments of the organophosphate insecticides phorate or disulfoton. The loss of chlorophyll and carotenoids with 6 days of 100 nM clomazone treatment of cotton seedlings was partially prevented with phorate in hydroponic solution in a rate-dependent manner. In a study to examine the timing of safening from a one-day clomazone (100 nM) treatment, maximum safening was achieved when phorate (50 μM) was applied the same day as clomazone. Phorate decreased metabolism of 14C-clomazone to polar metabolites in excised cotton shoots and shoots of intact cotton plants. Microsomal studies of corn shoots showed an NADPH-dependent/cytochrome P450 reaction was inhibited by phorate. Additional studies with corn microsomes, corn seedlings and cotton seedlings supported the basis of clomazone safening is the inhibition of toxic clomazone metabolism by P450 inhibitors.

The Potential for Clomazone Use in Rice (Oryza Sativa)

Clomazone was applied preplant incorporated, preemergence, delayed preemergence, or postemergence and compared to pendimethalin, quinclorac, and thiobencarb for control of barnyardgrass in rice. Seven days after the clomazone postemergence application, all clomazone treatments except those applied postemergence controlled barnyardgrass ≥ 86%. At 49 d after the postemergence application, control of barnyardgrass with 0.56 and 0.67 kg/ha clomazone postemergence improved to 92 and 93%, respectively. Clomazone and quinclorac applied delayed preemergence generally controlled barnyardgrass less than 70%. Visible injury to rice was ≤ 18% 7 d after emergence and had declined to less than 10% when evaluated 7 d after postemergence treatments. Rice yields were higher with all treatments compared to the nontreated control.

Weed Management in Transplanted Bell Pepper (Capsicum frutescens) with Clomazone and Rimsulfuron

In field studies, in 1993, 1994, and 1995, clomazone at 390 g ai/ha and rimsulfuron at 35 g ai/ha were evaluated preplant incorporated (PPI) and postemergence (POST), respectively, for weed control and crop response in transplanted ‘Keystone RG3’ bell pepper. Clomazone did not injure bell pepper. Common lambsquarters and jimsonweed control was 77 to 95% by clomazone treatments but was variable by rimsulfuron treatments at 41 to 93% common lambsquarters control and 42 to 68% jimsonweed control; common ragweed control by both herbicides was unacceptable. Injury by rimsulfuron to bell pepper in the field was 19 to 47% at 21 DAT. In the greenhouse, injury to Keystone RG3 and three additional bell pepper varieties, ‘Camelot,’ ‘Jupiter,’ and ‘Memphis’ was similar at 44 to 62% by rimsulfuron at 17 to 35 g/ha POST, and bell pepper had lower height and dry weight than untreated controls. In the greenhouse, jimsonweed control was below 49% and black nightshade control was below 23% by 17 to 35 g/ha rimsulfuron. In these studies, clomazone controlled common lambsquarters and jimsonweed without injury to bell pepper. The solanaceous weeds treated in this study were not well controlled by rimsulfuron, and bell pepper was not sufficiently tolerant to rimsulfuron to permit its use in this crop.

Efficacy of Clomazone Applied at Various Timings in Soybean (Glycine max)

Field studies conducted in 1991 to 1993 evaluated the efficacy of clomazone applied at various timings for weed control in soybean. Clomazone applied 45, 30, 15, or 0 days prior to planting (DPP) provided season-long control of velvetleaf and giant foxtail. In 1991 and 1992 clomazone alone 30 and 45 DPP failed to control redroot pigweed. Clomazone alone 45 DPP failed to control common lambsquarters. In 1991 and 1992 clomazone at 0.84 kg/ha plus metribuzin applied 45 DPP failed to control redroot pigweed. The addition of metribuzin plus chlorimuron to the above clomazone treatments resolved these weed control deficiencies. Weed control in 1993 was nearly complete across all clomazone treatments. In 1993 clomazone treatments which included metribuzin or metribuzin plus chlorimuron applied PPI or PRE reduced yield. Herbicide injury is the likely cause of this reduction because most treatments in 1993 provided 99% control of all weed species.

Clomazone volatilization under varying environmental conditions

Velvetleaf ( Abutilon theophrasti Medik.) was used as a bioindicator to examine factors (temperature, soil moisture, soil incorporation) which might influence clomazone {2-[(2-chlorophenyl)methyl] -4,4-dimethyl-3-isoxazolidinone} volatilization. Young plants were periodically exposed to atmosphere inside boxes containing clomazone-treated soil. Exposed plants were returned to the greenhouse for 5 to 7 d, and new leaves were assayed for chlorophyll. Maximum chlorophyll inhibition occurred in velvetleaf exposed during the first 2 wk after clomazone application. Reductions in degree of bleaching were first observed in plants exposed in the treatments with lower soil moisture (2% moisture at 19 days after clomazone treatment, DAT; 9% at 42 DAT). The least amount of clomazone was measured in soils incubated in the 35 °C treatment, indicating elevated temperatures enhanced volatilization, and may have contributed to the increased chlorophyll content observed observed earlier than other temperatures. The effect of herbicide incorporation was not conclusive.

Clomazone for Weed Control in Transplanted Cole Crops (Brassica oleracea)

Experiments were conducted at Lexington and Quicksand, KY, in 1989 and 1990 to determine the effect of preplant incorporated clomazone on weed control, crop injury, and yield of broccoli, cauliflower, green cabbage, red cabbage, and pak choi. Oxyfluorfen and trifluralin were included as standard treatments. Greater than 80% weed control was observed at both locations with 0.8 kg ai ha−1clomazone, with the exception of smooth pigweed at Lexington. All clomazone treatments caused crop injury 2 WAT. Injury was still evident 8 WAT at clomazone rates of 1.7 and 3.4 kg ha−1, but was minor with rates of 0.8 kg ha−1or less on broccoli, cauliflower, and red cabbage. Injury was less at Quicksand in both years and seasons over all clomazone rates, most likely due to higher soil organic matter content Yields of broccoli and cauliflower treated with 0.8 kg ha−1clomazone were similar to yields with oxyfluorfen on a 3% organic matter soil at Lexington in 1989. However, clomazone at 0.8 kg ha−1at Lexington reduced 1989 spring yields of green cabbage, red cabbage, and pak choi and 1990 spring yields of all cole crops as compared to oxyfluorfen. Clomazone at 0.8 kg ha−1at Quicksand reduced yield of green cabbage and pak choi in spring 1990 only on a 5.2% organic matter soil. Fall yields of broccoli and cauliflower in both years were not reduced by clomazone at 0.8 kg ha−1or less at either location. Our studies indicated potential for utilization of clomazone on cole crops in higher organic matter soils, especially if some early season crop injury and occasional yield loss can be tolerated.

Site of Clomazone Action in Tolerant-Soybean and Susceptible-Cotton Photomixotrophic Cell Suspension Cultures

Studies were conducted to determine the herbicidal site of clomazone action in tolerant-soybean (Glycine max [L.] Merr. cv Corsoy) (SB-M) and susceptible-cotton (Gossypium hirsutum [L.] cv Stoneville 825) (COT-M) photomixotrophic cell suspension cultures. Although a 10 micromolar clomazone treatment did not significantly reduce the terpene or mixed terpenoid content (microgram per gram fresh weight) of the SB-M cell line, there was over a 70% reduction in the chlorophyll (Chl), carotenoid (CAR), and plastoquinone (PQ) content of the COT-M cell line. The tocopherol (TOC) content was reduced only 35.6%. Reductions in the levels of Chl, CAR, TOC, and PQ indicate that the site of clomazone action in COT-M cells is prior to geranylgeranyl pyrophosphate (GGPP). The clomazone treatment did not significantly reduce the flow of [(14)C]mevalonate ([(14)C]MEV) (nanocuries per gram fresh weight) into CAR and the three mixed terpenoid compounds of SB-M cells. Conversely, [(14)C]MEV incorporation into CAR and the terpene moieties of Chl, PQ, and TOC in COT-M cells was reduced at least 73%, indicating that the site of clomazone action must be after MEV. Sequestration of clomazone away from the chloroplast cannot account for soybean tolerance to clomazone since chloroplasts isolated from both cell lines incubated with [(14)C]clomazone contained a similar amount of radioactivity (disintegrations per minute per microgram of Chl). The possible site(s) of clomazone inhibition include mevalonate kinase, phosphomevalonate kinase, pyrophosphomevalonate decarboxylase, isopentenyl pyrophosphate isomerase, and/or a prenyl transferase.

Growth and physiological responses of normal, dwarf, and albino corn ( Zea mays) to clomazone treatments

The effects of the bleaching herbicide clomazone (2-[(2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxazolidinone) on the growth of selected mutants of corn ( Zea mays L.) were evaluated. A normal hybrid (“Dekalb XL67”), a gibberellin-deficient dwarf-5 mutant, and a chlorophyll- and carotenoid-deficient albino ( lw 3 ) mutant of corn were exposed to clomazone applied preemergence at rates of 0.0, 0.3, 0.6, and 1.1 kg/ha under greenhouse conditions. Normal corn was very sensitive to clomazone treatments and was severely bleached. Shoot height, shoot dry weight, and chlorophyll content of normal corn were strongly inhibited by all application rates of clomazone. The effects of combined treatments of clomazone and the growth retardant CCC on the growth of normal corn were additive or synergistic. The clomazone induced retardation of the longitudinal growth of normal corn was reversed by exogenously applied gibberellin (GA 3). The dwarf-5 mutant exhibited a greater tolerance to clomazone than normal corn. Clomazone caused a slight chlorosis and reduced the longitudinal growth of this mutant only when applied at the highest rate of 1.1 kg/ha. The short-lived growth of the lethal albino mutant of corn was not affected significantly by clomazone. Normal and dwarf-5 corn responded quite differently when treated with the bleaching herbicide norflurazon. In contrast to the results obtained with clomazone, both normal and dwarf-5 corn were bleached severely by all rates of norflurazon but their shoot heights were not affected by this herbicide. Norflurazon reduced shoot dry weights of normal corn, but not of the dwarf-5 mutant. These results support previously published reports suggesting that clomazone acts by a new mechanism of bleaching action which is different than that of norflurazon. The lesser sensitivity of the gibberellin-deficient dwarf-5 mutant to clomazone and the reversal of clomazone-induced effects on normal corn by exogenous gibberellin suggest a secondary action of this herbicide on gibberellin biosynthesis.

Effects of Tillage on the Efficacy and Persistence of Clomazone in Soybean (Glycine max)

Experiments were conducted in 1985 to 1987 to evaluate the effects of conventional and no-tillage systems on the weed control provided by clomazone applied preemergence in soybeans. The persistence of clomazone in soil of the two tillage systems was also determined. Increasing the clomazone rate from 0.8 to 1.4 kg/ha did not increase weed control. Clomazone controlled 80% or more of jimsonweed, velvetleaf, and giant foxtail. Common cocklebur control ranged from about 50 to 70% in no-till and from 80 to 90% in conventional tillage. Generally, soybean pods/plant and yields were lower from clomazone treatments than from handweeded treatments due to inadequate common cocklebur control. Over 40% of the clomazone applied did not reach the soil surface; it was either intercepted by wheat straw, volatilized, or both. Clomazone persisted longer in conventional tillage than in no-tillage in. However, in 1986, clomazone was equally persistent in the two tillage systems. The half-life of clomazone was 34 and 6 days in 1985 in conventional and no-tillage, respectively, and in 1986, 18 and 16 days in conventional and no-tillage, respectively. Significant clomazone concentrations were not found below 10 cm in the soil profile. Corn planted without tillage (no-till) approximately 1 yr after clomazone application was not injured and yields were not reduced due to prior clomazone use.