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1.
Summary This research studied the influence of soil type, soil moisture and incubation time before rain on the mobility of imazaquin in two highly weathered tropical soils, named clay and sandy clay. The soils were packed in glass columns and treated at three different moisture contents. Then, the applied imazaquin (150 g a.i. ha−1) was incubated for 0, 1 and 30 d before rainfall simulation began. Leaching was significantly higher in the sandy clay soil, when imazaquin was applied to moist samples and rainfall occurred soon after application (in this case, 73.4% of applied imazaquin was leached). Leaching was always low in the clay soil (in all cases, <1.8% of applied imazaquin was leached). In addition, imazaquin leaching potential was overestimated by the low K d value (1.24 L kg−1) measured for the clay soil using batch equilibration data. For this soil, the vacuum displacement method also failed to predict leaching (in this case, 28.9% of applied imazaquin was leached). Consequently, batch equilibration and vacuum displacement methods cannot be used to predict leaching of anionic organic molecules, such as imazaquin, in fine-textured tropical soils. Moreover, soil type and weather patterns or irrigation timing must be considered before imazaquin application to avoid environmental or carry-over problems and to achieve maximum effectiveness of the herbicide.  相似文献   

2.
精异丙甲草胺在土壤中的吸附行为及 环境影响因素研究   总被引：1，自引：1，他引：1  
采用平衡振荡法研究了精异丙甲草胺在粘壤土、粘土及砂壤土中的吸附和解吸附行为。结果表明,3种土壤的吸附等温线均属L型并符合Freundlich模型,吸附常数(Kf)分别为4.01、6.15及8.62,且Kf 和1/n(n为经验常数)的乘积与土壤有机质含量呈正相关性。解吸附实验结果表明,精异丙甲草胺在土壤中的解吸附与吸附并不一致,显示出明显的滞后性。温度及pH值等环境因素对吸附影响的结果显示,随温度升高精异丙甲草胺在土壤中的吸附量有所减少,中性环境下土壤吸附量较低。  相似文献   

3.
ROUCHAUD  NEUS  CALLENS  & BULCKE 《Weed Research》1998,38(5):361-371
Sulcotrione soil persistence in spring maize ( Zea mays L.) crops grown on a sandy loam soil was greater at pH 5·5 and 6·0 (soil half-life T 1/2≈58 days) than at pH 7·1 ( T 1/2 = 44 days). Sulcotrione was also applied as recommended on a summer maize crop at the five- to six-leaf growth stage, grown on a sandy loam soil. Sulcotrione soil half-life was 44 days, and the herbicide remained mainly in the 0- to 5-cm surface soil layer during the cropping period, in spite of the high water solubility and the heavy rains at the end of August; lower sulcotrione concentrations (10–18% of the total during the 2-month period after sulcotrione application) were detected in the 5- to 10-cm surface soil layer. The herbicide was applied pre-emergence to winter wheat ( Triticum aestivum L.) at four sites that differed in their soil texture and composition: loamy sand, sandy loam, loam and clay loam. Persistence was greater in the soils containing more organic matter. In soils having similar organic matter contents, persistence was lower in the soil containing more sand relative to loam and clay. During the winter crops, sulcotrione moved down to the 10- to 15-cm soil layer, in spite of the fact that the rains were lower in winter than in summer. Sulcotrione most generally was not detected in the 15–20 cm soil layer of the maize and winter wheat crops.  相似文献   

4.
The effects of a range of concentrations of four nutrients – nitrogen, phosphorus, potassium and calcium – in fertilizer solutions on the severity of anthracnose on strawberry cv. Nyoho cultivated under a noncirculation hydroponics system were determined after inoculation with Colletotrichum gloeosporioides . Crop growth and tissue nitrogen, phosphorus, potassium and calcium contents of the entire above-ground parts of the plant were also investigated. Elevated nitrogen and potassium concentrations in the fertilizer solution increased disease severity in contrast to phosphorus and calcium. Treatment with either NH4 or NO3 nitrogen was not significantly different. The dry weight of the strawberry plants increased significantly with elevated concentrations of nitrogen ( R 2 = 0·9078) and phosphorus ( R 2 = 0·8842), but was not influenced by the elevated amounts of potassium ( R 2 = 0·8587) and calcium ( R 2 = 0·6526) concentrations.  相似文献   

5.
Isoxaflutole is a new pre-emergence corn herbicide which controls both grass and broadleaf weeds. Experiments were performed in the laboratory to study the sorption of isoxaflutole in five different soils (Moorhead, MN; East Monroe, CO; Ellendale, MN; South Deerfield, MA; and Chelsea, MI) using the batch equilibration technique. Total initial isoxaflutole solution concentrations for each soil were 0.05, 0.15, 0.3. 0.8, 1.5, 2.0 and 4.0 mg litre−1. Analysis of [ring-14C] isoxaflutole was performed using liquid scintillation counting, and sorption data were fitted with the Freundlich model. Isotherms of isoxaflutole in all the soils were non-linear as depicted by the exponent (n < 1.0), indicating differential distribution of sorption site energies in various soils. Since the isotherms were non-linear the data fit Freundlich's isotherm well, as was indicated by high values of the regression coefficient (r2). The Freundlich sorption coefficient ranged from 0.555 to 50.0 (litre nmg l−nkg−1). Multiple regression of the sorption constant, KF against selected soil properties indicated that organic matter content was the best single predictor of isoxaflutole sorption (r2 = 0.999) followed by soil pH (r2 = 0.954). Clay content of the soils did not have a high correlation with KF values (r2 = 0.453), while the sorption of isoxaflutole was not influenced by the Ca2+ concentration in the soil solution. Isoxaflutole sorption increased with an increase in organic matter content of soils. Sorption of isoxaflutole decreased as the soil pH increased from 4.5 to 8.5, which was depicted by the reduction of KF values. Sorption of isoxaflutole to the soils varied with differences in binding energies. At a particular net energy value (E*), the corresponding site energy distribution [F(E*)] values followed the order, Chelsea, MI > Moorhead, MN > East Monroe, CO > South Deerfield, MA > Ellendale, MN. The negative magnitude of Gibbs free energy of sorption (ΔG x) indicates the spontaneity of the given sorption process in the soils from Moorhead, MN; East Monroe, CO and Chelsea, MI. © 1999 Society of Chemical Industry  相似文献   

6.
DONALD 《Weed Research》1998,38(6):425-431
The research goal was to determine whether crop damage from herbicides measured early in the growing season soon after treatment could be used to estimate relative crop yield loss. Percentage stunting was rated visually and percentage crop ground cover (i.e. percentage of the ground surface covered by vegetation) was determined from video photographs taken 2–4 weeks after sethoxydim-susceptible maize ( Zea mays L.) was sprayed with sethoxydim at various rates plus crop oil concentrate. Averaged over 3 years, relative percentage maize yield was a negative sigmoidal function of relative sethoxydim rates from 0.065× to 0.5×, where the 1× rate was 420 g a.i. ha−1 ( r 2 = 0.80). Relative maize yield was positively linearly related to percentage crop ground cover and negatively linearly related to rated percentage stunting averaged over 3 years. Linear regression models of relative maize yield vs. percentage maize ground cover explained only slightly more data variability ( r 2 = 0.86) than did rated stunting ( r 2 = 0.82) over 3 years. The advantages and disadvantages of rated stunting and crop ground cover as scientific measurements are discussed.  相似文献   

7.
Isoxaflutole is a relatively new herbicide used for weed control in maize. The objective of this research was to increase the understanding of the behaviour and environmental fate of isoxaflutole and its diketonitrile (DKN) degradate in soil, including determination of the strength of sorption to soil and whether sorption is affected by ageing. In sandy loam (SL) and silty clay (SiCl) soils, 14C‐isoxaflutole was found to dissipate rapidly after application to soil; recovery ranged from ～42% to 68% at week 0, and recovery had decreased to <10% at week 12. Decreases in 14C isoxaflutole residues over time in SL and SiCl soils are consistent with hydrolysis of isoxaflutole and formation of bound DKN residues in the soil. DKN recovery from freshly treated SiCl and SL soils was 41% to 52%. After a 12‐week incubation in SL soil at pH 7.1 and 8.0, recoveries were similar, ～40%. However, at week 12 in SL soil pH 5.7, DKN recovery decreased to ～28%. DKN recovery in SiCl soil at week 12 was <10%. Increases in sorption of DKN in SL at pH 5.7 and SiCl soil over time indicate that the DKN degradate is tightly bound to the soil and sorption is affected by soil pH and soil type. Sorption of 14C‐DKN in the SiCl soil more than doubled with ageing compared with the lower Kd sorption coefficient values of the SL soils. In the SiCl soil at time 0, the Kd was 0.6; at 1 week, Kd increased to 2; and at the end of the 12‐week incubation period, Kd was 4.5. This strong binding of DKN to the soil may be due to chelate formation in the interlayer of the clay.  相似文献   

8.
R. GROVER 《Weed Research》1968,8(3):226-232
Summary. Effective dosages of picloram (4–amino-3,5,6–trichloropicolinic acid) required to reduce fresh weight of sunflowers ( Helianthus annuus L. var. Menonite) were determined for seven Saskatchewan soils under controlled environmental conditions. The relationships between ED50 value and clay content, organic matter content and cation exchange capacity were evaluated by correlation and regression analysis for possible usefulness in predicting dose requirements. ED50 values were also determined for Weyburn loam and in culture solutions adjusted to various pH levels.
There Was no significant correlation between ED50 values of picloram and soil clay content or cation exchange capacity. ED50 values were highly correlated with soil organic matter content, and they increased as the soil pH was lowered or raised from pH 6.5. The increase in ED50 values in the acidic range was attributed to adsorption of the unionized molecules of picloram on the organic matter in the soil. The increase in ED50 values in the alkaline range may be mainly due to reduced uptake of the ionized acid by plant roots.  相似文献   

9.
Adsorption-desorption studies of metalaxyl in fifteen agricultural soil samples from Southern Portugal and Spain were performed following a batch equilibration method. Very high sorption was observed on a clay soil of high content in altered illite, but, when this soil was excluded from regression analysis, organic matter (OM) was the most important single soil property affecting sorption at low concentrations of metalaxyl. At higher concentrations, no correlation was observed with any soil property. The relevance of OM on sorption was also corroborated by the increase in sorption coefficients when soil OM was increased artificially by the addition of an organic amendment. Sorption studies with the colloidal fraction of selected soils also revealed the importance of mineral surfaces in metalaxyl sorption. Sorption of metalaxyl in most of the soil samples was hysteretic. Selected soil samples were incubated in the dark, sampled periodically and extracted for their fungicide content. Metalaxyl half-lives increased with sorption and OM content of the soil, and were specially high in the amended soil. Leaching studies in hand-packed columns under saturated/unsaturated flow conditions showed an inverse relation between leaching and sorption. Recoveries from the soil columns were close to 80% of the metalaxyl applied, except for the soil which OM was artificially increased, in which recovery was lower and this has been attributed to the much higher irreversibility of metalaxyl sorption in the amended soil.  相似文献   

10.
Metalaxyl and tricyclazole are two fungicides widely used in Spain in vineyard and rice crops respectively. In this study an investigation has been made of the effect of three organic amendments [two commercial amendments, solid fertiormont (SF) and liquid fertiormont (LF), and a residue from the olive oil production industry, alperujo (OW)] on fungicide fate in soils. Changes in soil porosity on amendment were studied by mercury intrusion porosimetry, sorption-desorption studies were performed by the batch equilibration method, dissipation of metalaxyl and tricyclazole in the soil was studied at - 33 kPa moisture content and 20 degrees C and leaching was studied in hand-packed soil columns. Amendments with SF and LF reduced soil porosity, while OW increased porosity through an increase in pore volume in the highest range studied. Tricyclazole sorbed to soils to a much higher extent than metalaxyl. With some exceptions, sorption of both fungicides increased on amendment, especially in the case of SF-amended soils, which rendered the highest K(oc) values. In soils amended with the liquid amendment LF, sorption either remained unaffected or decreased, and this decrease was much higher in the case of metalaxyl and a soil with 70% clay. In this clay soil, amendment with OW, of very high soluble organic matter content, also decreased metalaxyl sorption. Tricyclazole is more persistent in soil than metalaxyl, and both fungicides were found to be more persistent in amended soils than in unamended soils. Leaching of metalaxyl and tricyclazole in soil columns was inversely related to sorption capacity. The low recoveries of tricyclazole in leachates and in soil columns when compared with metalaxyl, a less persistent fungicide, were attributed to diffusion into micropores and to increase in sorption with residence time in the soil, both processes favoured by the low mobility of tricyclazole.  相似文献   

11.
BACKGROUND: Sorption largely controls pesticide fate in soils because it influences its availability for biodegradation or transport in the soil water. In this study, variability of sorption and desorption of isoxaflutole (IFT) and its active metabolite diketonitrile (DKN) was investigated under conventional and conservation tillage. RESULTS: According to soil samples, IFT KD values ranged from 1.4 to 3.2 L kg?1 and DKN KD values ranged from 0.02 to 0.17 L kg?1. Positive correlations were found between organic carbon content and IFT and DKN sorption. IFT and DKN sorption was higher under conservation than under conventional tillage owing to higher organic carbon content. Under conservation tillage, measurements on maize and oat residues collected from the soil surface showed a greater sorption of IFT on plant residues than on soil samples, with the highest sorbed quantities measured on maize residues (KD ≈ 45 L kg?1). Desorption of IFT was hysteretic, and, after five consecutive desorptions, between 72 and 89% of the sorbed IFT was desorbed from soil samples. For maize residues, desorption was weak (<50% of the sorbed IFT), but, after two complementary desorptions allowing for IFT hydrolysis, DKN was released from maize residues. CONCLUSION: Owing to an increase in organic carbon in topsoil layers, sorption of IFT and DKN was enhanced under conservation tillage. Greater sorption capacities under conservation tillage could help in decreasing DKN leaching to groundwater. Copyright © 2012 Society of Chemical Industry  相似文献   

12.
Isoxaflutole is a new pre‐emergence herbicide for use in maize and sugarcane. Its two main derivatives are a diketonitrile derivative, the 2‐cyano‐3‐cyclopropyl‐1‐(2‐methanesulfonyl‐4‐trifluoromethylphenyl)propan‐1,3‐dione, named DKN, and a benzoic acid derivative, the 2‐methanesulfonyl‐4‐trifluoromethylbenzoic acid, named BA. The adsorption/desorption processes have never been studied for isoxaflutole (IFT) at high concentrations nor for BA, and the present work aimed at completing the knowledge of the behaviour of these three molecules in conditions close to those encountered in the context of agricultural use. The adsorption/desorption study was conducted on seven soils of different physical and chemical properties, using the batch equilibrium technique. During the experiments, IFT was chemically converted into DKN in a continuous manner. This reaction appeared to be dependent on the pH of the soil and was taken into account in the calculations of the adsorbed and desorbed amounts. The adsorption isotherms obtained were predominantly C‐shaped for IFT and DKN and S‐shaped for BA, but some differences appeared on a few soils. They fitted well the Freundlich equation, and the values of the Freundlich coefficient Kfa showed that, whatever the soil, IFT was more adsorbed than its two derivatives. The main parameter influencing the adsorption of IFT appeared to be the organic matter content, whereas this effect was not evident for DKN and BA. No correlation was found between the extent of adsorption and either clay content or pH of the soil, for the three molecules.  相似文献   

13.
Summary. When columns of three soil types were perfused with a microbial medium containing 5·7 and 26·9 ppm 14COOH-labelled chloramben, there was a rapid decrease in the 14C activity remaining in solution, attributable to soil adsorption. Soil pH and organic matter content were the primary factors controlling chloramben adsorption. Soil pH may enhance adsorption through its effect on the number of soil anion exchange sites, and sites for polyvalent cation bridging and H bonding. Following adsorption, liver decreases in solution 14C-chloramben activity were attributed to degradation; 14CO2 evolved during perfusion amounted to 25–30% of the total decrease in 14C-chloramben from solution. It was concluded that more than 90% of the 14C-activity remaining in solution could be attributed to intact chloramben. Thus, decarboxylation appeared to be the primary mechanism of chloramben degradation in soils. Lag phases observed during degradation and subsequent investigations with re-amended solutions implicated the soil microflora; even at chloramben concentrations of 26.9 ppm no toxic effect on the chloramben-degrading micro-organisms was apparent.
Dégradation du chlorambène [amibène) dans le sol  相似文献   

14.
Adsorption-desorption of the herbicide flufenacet (FOE 5043) has been studied in five soils from different locations in India (Delhi, Ranchi, Nagpur, Kerala and Assam) varying in their physicochemical properties. The organic matter (OM) content varied from 0.072 to 0.864%, clay content from 2.5 to 43.7% and pH from 4.45 to 8.35. The adsorption studies were carried out using a batch equilibration technique. Ten grams of soil were equilibrated with 20 ml of aqueous 0.01 M CaCl2 solution containing different concentrations (0-30 mg litre-1) of flufenacet. After equilibration, an aliquot of supernatant was taken out for analysis. During desorption, the amount withdrawn for analysis was replenished with fresh 0.01 M CaCl2 solution and further equilibrated. Desorption studies were carried out with the 30 mg litre-1 concentration of flufenacet only. The adsorption studies revealed that there was moderate to high adsorption of flufenacet considering the comparatively low organic carbon content in the five test soils. Average Kd values ranged from 0.77 to 4.52 and Freundlich KF values from 0.76 to 4.39. The highest adsorption was observed in Kerala soil (OM 0.786%; clay 25%; pH 4.45) followed by Ranchi, Nagpur and Delhi soils, and the lowest in Assam soil (OM 0.553%; clay 2.5%; pH 6.87). The trend in adsorption could be attributed to the chemical nature of flufenacet and the physicochemical properties of the soil such as pH, OM and clay contents. OM and clay contents were positively correlated whereas pH was negatively correlated. Soils having low pH, high OM and high clay contents showed higher adsorption. Desorption studies revealed that there was a hysteresis effect in all the soils. Hysteresis coefficient values (ratio of n(ad) and n(des)) varied from 0.09 to 0.45. The study implies that, because of its moderate to high adsorption, flufenacet is likely to persist in soil for some time. However, the possibility of its movement by leaching or surface run off is less.  相似文献   

15.
The effects of different inocula of the mycoparasite Coniothyrium minitans on carpogenic germination of sclerotia of Sclerotinia sclerotiorum at different times of year were assessed. A series of three glasshouse box bioassays was used to compare the effect of five spore-suspension inocula of C. minitans , including three different isolates (Conio, IVT1 and Contans), with a standard maizemeal–perlite inoculum. Apothecial production, as well as viability and C. minitans infection of S. sclerotiorum sclerotia buried in treated soil, were assessed. Maizemeal–perlite inoculum at 107 CFU per cm3 soil reduced sclerotial germination and apothecial production in all three box bioassays, decreasing sclerotial recovery and viability in the second bioassay and increasing C. minitans infection of sclerotia in the first bioassay. Spore-suspension inocula applied at a lower concentration (104 CFU per cm3 soil) were inconsistent in their effects on sclerotial germination in the three box bioassays. Temperature was an important factor influencing apothecial production. Sclerotial germination was delayed or inhibited when bioassays were made in the summer. High temperatures also inhibited infection of sclerotia by C. minitans . Coniothyrium minitans survived these high temperatures, however, and infected the sclerotia once the temperature decreased to a lower level. Inoculum level of C. minitans was an important factor in reducing apothecial production by sclerotia. The effects of temperature on both carpogenic germination of sclerotia and parasitism of sclerotia by C. minitans are discussed.  相似文献   

16.
BACKGROUND: The fate of isoxaflutole (IFT) in soil is closely related to soil sorption. Sorption and transformation of IFT were investigated in laboratory incubations with four soils, and these results were used to interpret greenhouse studies using IFT to control several weed species. RESULTS: Degradation proceeded by previously observed pathways to form diketonitrile (DKN) and benzoic acid (BA) derivatives, as well as traces of unidentified products. Over the course of the incubation, DKN was the dominant active form of the herbicide present in the experimental system, and was thus critical to the soil activity of the herbicide for weed control. CONCLUSION: Control of most weed species appeared to be a function of both sorption and biodegradation of DKN, with greatest weed control being observed in soils in which a significant portion of the DKN that was formed persisted and remained bioavailable over the course of the incubation. Copyright © 2009 Society of Chemical Industry  相似文献   

17.
Current status of biological control of paddy weeds in Vietnam   总被引：1，自引：0，他引：1  
Rice is a staple food in Vietnam and accounts for > 7.7 × 106 cultivated ha, which provide 35.5 × 106 t of rice, of which 4.2 × 106 t were exported in 2004. The enlargement of the cropping area and the enhancement of rice yield have rapidly increased the amount of agrochemicals, including herbicides, in crop production in Vietnam. From 1990–2003, the percentage of herbicides in total pesticides has increased ≈ 10-fold to 30.2%. In addition, the improper use of herbicides caused environmental hazards, unsafe agricultural products, and human health problems. Biological management integrated with traditional weed control techniques might help to reduce the dependence on synthetic herbicides and build eco-friendly, sustainable agricultural production in Vietnam. This paper reviews the efforts in establishing a strategy for biological management of weeds that was conducted in recent years by Vietnamese weed scientists. This has included cropping system management, water and soil management, integrated pest management, and utilization of plant allelopathy as major components of the strategy. Many plants with strong allelopathic potential can be a source for biological weed suppression and soil fertility improvement. The utilization of allelopathic properties in rice might also help to provide new rice cultivars with weed-suppressing characteristics.  相似文献   

18.
The effects of Coniothyrium minitans inoculum quality and an 8-week interval between inoculum application and crop planting on sclerotinia ( Sclerotinia sclerotiorum ) disease in three successive lettuce crops were investigated in a glasshouse trial. Spore suspensions of three isolates of C. minitans (Conio, IVT1 and Contans) applied at 108 CFU m−2 and a standard Conio maizemeal–perlite application (06 L m−2, 1011 CFU m−2) were assessed for their ability to control S. sclerotiorum . Only the maizemeal–perlite inoculum (isolate Conio) consistently reduced sclerotinia disease. In the third lettuce crop only, isolates IVT1 and Contans formulated by Prophyta and isolate IVT as an oil–water formulation, all applied as spore suspensions, reduced disease at harvest compared with the untreated control. Recovery, viability and C. minitans infection of sclerotia buried during the 8-week period prior to each of the three lettuce crops, and of sclerotia formed on the crop, were tested. Only the maizemeal–perlite inoculum (isolate Conio) reduced the recovery of sclerotia buried in soil for weeks between inoculum application and crop planting, reducing their viability and increasing infection by C. minitans . Eight weeks was sufficient to enable C. minitans to infect sclerotia of S. sclerotiorum , and may account for disease control. After harvest of the second and third crops, maizemeal–perlite treatment (isolate Conio) reduced the number and viability of sclerotia recovered on the soil surface and increased infection by C. minitans compared with spore-suspension treatments. The effect of inoculum concentration and the influence of soil temperature (varying with time of year) on infection of sclerotia by C. minitans are discussed.  相似文献   

19.
Sorption and leaching potential of herbicides on Brazilian soils   总被引：1，自引：0，他引：1  
Sorption of the herbicides alachlor, atrazine, dicamba, hexazinone, imazethapyr, metsulfuron-methyl, nicosulfuron, simazine and sulfometuron-methyl was characterized on six Brazilian soils, using the batch equilibration method. In general, weak acid herbicides (dicamba, imazethapyr, metsulfuron-methyl, nicosulfuron and sulfometuron-methyl) were the least sorbed, whereas weak bases such as triazines and nonionic herbicides (alachlor) were the most sorbed. The Kd values found showed a significant correlation with soil organic carbon content (OC) for all herbicides except imazethapyr and nicosulfuron. Koc values showed a smaller variation among soils than Kd . To estimate the leaching potential, Koc and the ground-water ubiquity score (GUS) were used to calculate half-lives ( t1/2 ) that would rank these herbicides as leachers or non-leachers. Comparison of calculated values to published values for t1/2 demonstrated that sulfonylureas and hexazinone are leachers in all soils, alachlor is transitional, and atrazine, simazine and dicamba are leachers or transitional, depending on soil type. Results discussed in this paper provide background to prioritize herbicides or chemical groups that should be evaluated in field conditions with regard to their leaching potential to ground-water in tropical soils.  相似文献   

20.
Flumioxazin adsorption kinetics were described using a Greenville sandy clay loam soil. Adsorption kinetics experiments showed that 72% of total herbicide was absorbed after 1 h of continuous shaking and continued to increase to 78% after 72 h. Flumioxazin adsorption was then tested on seven agriculturally important soils throughout the southern USA. Adsorption isotherms for all soils had K(f) (Freundlich distribution coefficient) values that ranged from 8.8 to 0.4, with many near 1.5. Soil organic matter content was the parameter most highly correlated with flumioxazin adsorption (r(2) = 0.95, P < 0.001). Sorption to clay minerals had K(f) values ranging from 50 for bentonite to 4.7 for kaolinite. However, normalizing K(f) for sorbent surface area revealed that aluminum hydroxide (gibbsite) possessed the greatest flumioxazin sorption per unit area. Sorption to anionic exchange resin (K(f) 676) was greater than cationic exchange resin (K(f) 42). Molecular model calculations were performed to elucidate why sorption was greater to anionic exchangers. These calculations indicated that a region of dense electronegativity exists on the 3-dione moiety of the molecule. This would lead to greater flumioxazin sorption by positively charged surface sites. Desorption isotherms from soil exhibited no effect of hysteresis. Desorption from clay minerals was very rapid and flumioxazin in solution was undetectable after three desorption steps. From these data it was concluded that flumioxazin can become readily available in soil solution with increase in soil water content.  相似文献   

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