Effect of CPC,Brij-35, and SDBS Surfactants on the Adsorption and Movement of Carbofuran in Indian Soils

Laboratory studies were conducted to determine adsorption and movement of carbofuran in aqueous surfactant-free and surfactant [(cationic, cetyl pyridinium chloride (CPC), non-ionic, polyoxyethylene lauryl ether (Brij-35) and anionic, sodium dodecyl benezene sulphonate (SDBS)] solutions of different critical micellar concentrations (1/2 × CMC, 1.0 × CMC, and 2 × CMC) in four different Indian soils using batch shake and soil thin layer chromatography (soil TLC) techniques. The measured equilibrium adsorption isotherms were in agreement with the Freundlich equation. Higher adsorption of carbofuran in both systems was observed on FRI silt loam (FSL) soil followed by Alampur silt loam (ASL), Kalai loam (KL), and Bhoran sandy loam (BSL) soils, as anticipated from Freundlich constant K_F and distribution coefficient K_D, in surfactant-free systems and K_F* and K_D* in surfactant-soil-water systems. The adsorption of carbofuran in surfactant-soil-water systems followed the order cationic > anionic > non-ionic at all CMCs studied. The R_f values obtained from soil TLC studies confirmed the above order of adsorption. The K_D and K_D* values were used to evaluate remediation efficiency (K_D*/K_D) of surfactants. Non-ionic surfactant, Brij-35, and anionic surfactant, SDBS, are favorable for remediating soil contaminated with carbofuran as K_D*/K_D ratio is less than 1.     

A comparison of fine root distribution and water consumption of mature Caragana korshinkii Kom grown in two soils in a semiarid region, China

Water is a key limiting factor for vegetation restoration in the semi-arid areas of China. Caragana korshinkii Kom is a shrub that is widely planted in this region to control soil erosion and land desertification. The objective of this study was to investigate the fine root distribution of mature C. korshinkii and its water consumption, when grown in either silt loam or sandy soils, in order to understand differences between the water cycles of two such soils found in the transition zone between fertile loess hills and desert of the Northern Loess Plateau. Fine root distributions were measured using the trench-profile method. Soil water dynamics were monitored with a neutron probe during two growing seasons. The results showed that fine root area density (FRAD) declined with increasing soil depth in both soils, with 70.7% and 96.6% of the total fine roots being concentrated in the upper 1-m layer of the silt loam and sandy soils, respectively. Water consumption by C. korshinkii in the silt loam was close to that in the sandy soil. Most water consumption in both soil types was from the upper 1-m layer. Little variation in plant available water (PAW) occurred in the 3–6 m soil layer during the whole study period. However, in this layer, the PAW was significantly lower in the silt loam soil than in the sandy soil. Total actual evapotranspiration (ET_a) was slightly higher from the sandy soil plots than from those of the silt loam soil during both growing seasons. Our study indicated that mature C. korshinkii effectively uses about the same amount of water from either the silt loam or sandy soils, but that more soil water at depth was extracted from silt loam soil than from sandy soil.     

Fertilizer vs. organic matter contributions to nitrogen leaching in cropping systems of the Pampas: 15N application in field lysimeters

Nitrogen (N) export from soils to streams and groundwater under the intensifying cropping schemes of the Pampas is modest compared to intensively cultivated basins of Europe and North America; however, a slow N enrichment of water resources has been suggested. We (1) analyzed the fate of fertilizer N and (2) evaluated the contribution of fertilizer and soil organic matter (SOM) to N leaching under the typical cropping conditions of the Pampas. Fertilizer N was applied as ¹⁵N-labeled ammonium sulfate to corn (in a corn/soybean rotation) sown under zero tillage in filled-in lysimeters containing two soils of different texture representative of the Pampean region (52 and 78 kg N ha^-1, added to the silt loam and sandy loam soil, respectively). Total fertilizer recovery at corn harvest averaged 84 and 64% for the silt loam and sandy loam lysimeters, respectively. Most fertilizer N was removed with plant biomass (39%) or remained immobilized in the soil (29 and 15%, for the silt loam and sandy loam soil, respectively) whereas its loss through drainage was negligible (<0.01%). We presume that the unaccounted fertilizer N losses were related to volatilization and denitrification. Throughout the corn growing season, subsequent fallow and soybean crop, which took place during an exceptionally dry period, the fertilizer N immobilized in the organic pool remained stable, and N leaching was scarce (7.5 kg N ha^-1), similar at both soils, and had a low contribution of fertilizer N (0–3.5%), implying that >96% of the leached N was derived from SOM mineralization. The inherent high SOM of Pampean soils and the favorable climatic conditions are likely to propitiate year-round production of nitrate, favoring its participation in crop nutrition and leaching. The presence of ¹⁵N in drainage water, however, suggests that fertilizer N leaching could become significant in situations with higher fertilization rates or more rainy seasons.     

Effect of long-term application of animal manure on physical properties of three soils

Surface soil samples to 15 cm depth were taken from replicated plots in an ongoing long-term field experiment involving application of animal manure on three soils in Virginia. The sampled plots had received either no manure or the equivalent of 289,000 kg ha^–1 of manure as dry weight. The manure was applied annually at the beginning of each spring for 15 years from 1978 through 1992. The plots were cropped similarly since 1978. Soil textures were a fine sandy loam at Holland in the Atlantic Coastal Plain region, a silt loam at Blacksburg in the Appalachian region, and a clay loam at Orange in the Piedmont region of Virginia. The following measurements were made on subsamples: liquid and plastic limits, wet aggregate stability, aggregate size distribution, dispersible clay percentage, water retention at 0. 03, 0.1, 0.3, 0.5, 1.0, and 1.5 MPa tension, and modulus of rupture of moulded briquettes at a water content corresponding to 0.1 MPa tension. Organic matter content by the Walkley-Black method was significantly higher in the manure-treated soils at all three locations. Increases were 3% for the sandy loam and 25% for the silt loam and clay loam. From these values it was estimated that at least 95% of the total applied manure had been degraded over the 15 years. Results showed that the liquid and plastic limits for all three soils were higher (p<0.05) for the manure-treated samples. However, the differences in the limits were only 2 to 3%. The modulus of rupture values were lowered by addition of the animal manure. Decreases (p<0.05) occurred for the silt loam and clay loam samples. The wet aggregate stability increased and the dispersible clay decreased in the manure-treated soils. Increases (p<0.05) in wet aggregate stability occurred for the sandy loam and silt loam samples. Decreases (p<0.05) in dispersible clay were measured for the sandy loam and clay loam samples. Water retention was consistently, but only slightly, increased by manure addition. The increases, in the order of sample texture, were clay loam > sandy loam silt loam. Increases tended to be higher at the lower values of tension. Manure addition consistently increased the weight percentages of aggregates passing a given mesh size. Increases, in order of sample texture, were silt loam > clay loam > sandy loam. In their entirety, these results show that the manure produced measurable changes in the soil physical properties. The magnitude of the changes, in most cases, were small and depended on the soil texture. Given the high total amount of manure applied, the results indicate that manure-induced physical changes in the soil were small and evidently did not accumulate over time. Rapid microbial degradation of the manure could be responsible for the lack of marked changes in the soil physical properties.     

Feeding inhibition and mortality in Reticulitermes flavipes (Isoptera: Rhinotermitidae) after exposure to imidacloprid-treated soils

Feeding inhibition and mortality of Reticulitermes flavipes (Kollar) exposed to sand, sandy loam, loam, and silty clay loam soils treated with several concentrations of imidacloprid were studied using bioassay techniques under laboratory conditions. Termite workers stopped feeding after exposure to treated soils. Differences in feeding reduction varied among the soil types. Based on the magnitude of the F-statistics, the effect of imidacloprid on the reduction of termite feeding was greatest in sand followed by sandy loam, loam, and silty clay loam soils. Soil properties such as organic matter content, silt and clay proportions, pH, and cation exchange capacity were suggested to affect the bioavailability of imidacloprid. Similar soil effects on mortality were observed in termites continuously exposed to treated soil for 21 d. In three of four soils tested, susceptibility to imidacloprid was not affected by the source of the termites tested.     

Effect of Burkholderia (Pseudomonas) cepacia and soil type on the control of crown rot in wheat

A rifampicin-resistant isolate of Burkholderia (Pseudomonas) cepacia (A3R) reduced crown rot (Fusarium graminearum Group 1) symptoms significantly (P 0.05) in wheat in glasshouse and field experiments and increased grain yield significantly (P 0.05) in one of two field experiments. In glasshouse experiments, applying the bacteria as a soil drench (2.5 × 109 cfu/g soil) was more effective than coating the bacteria on wheat seed (3.4 × 107cfu/seed). In field experiments, the bacteria were applied as a soil drench at the rate of 1.8 x 10¹⁰ cfu/m row. In both the glasshouse and the field, disease severity in the bacteria-inoculated treatments was significantly less in a silt loam than in a sandy loam. The silt loam had a large proportion of fine clay and silt particles (51.7%), which may have favoured the biocontrol activity and survival of the introduced B. cepacia. In a glasshouse experiment, control by B. cepacia was significantly greater in the silt loam than in the sandy loam, which in turn was greater than in a loamy sand. The loamy sand appeared to favour crown rot development but not the activity or survival of the bacterial antagonist. The latter was reflected by the relative populations of the rifampicin-resistant bacteria re-isolated from the various soils during a 5-week period after application of the bacteria (silt loam > sandy loam > loamy sand). This study further confirms that soil type can influence the populations and the level of biocontrol activity of some bacterial antagonists.     

Microbial biosurfactant mediated removal and/or solubilization of crude oil contamination from soil and aqueous phase: An approach with Bacillus licheniformis MTCC 5514

This study highlights the role of marine microbial biosurfactants on solubilization/removal of crude-oil contamination from four different soils in an aqueous phase. Soil of four different types, viz., sandy, fine sand soil, clay, and clay loam, were collected and saturated with crude oil. Marine isolate MTCC 5514 (Bacillus licheniformis) was chosen for the study and comparisons were made with synthetic surfactants and commercially available biosurfactant. In-situ studies were carried out with different percentages of crude oil to assess the growth and the percentage removal of oil. For ex-situ studies, soils were pre-saturated with crude oil and then treated with the chosen biosurfactant at a 10% concentration level using flask and column methods. After time intervals of 30–120 min, samples were collected and then subjected to extraction with hexane and the percentage removal was calculated. Results revealed, at 2% concentration of crude oil, that complete solubilization was achieved. With regard to ex-situ studies, clay soil absorbed the maximum percentage of oil compared to other soil types, and with regard to the removal, all the synthetic surfactants showed <60% removal irrespective of soil type. In the case of biosurfactants even at 10% concentration, >85% removal was achieved.     

Fate of virus in wastewater applied to slow-infiltration land treatment systems

The removal of seeded coliphage f2 and indigenous enteroviruses from primary and secondary wastewaters applied by spray irrigation to sandy loam and silt loam soils in field test cells was examined. The amount of f2 recovered from 170-cm-deep soil percolate samples taken over a 53-day period never exceeded 0.1% of applied virus levels and was usually below detection limits. Indigenous enterovirus levels in percolate waters also constituted only a small portion of those found in the wastewaters. At 10 days after seeding, f2 virus was present throughout the soil column but tended to accumulate around the soil core middepths. Coliphage f2 disappeared from the soil surface regions at a high rate, and by 53 days very little virus could be detected within the length of the soil columns. Sterilized soil core segments from different depths were studied to determine their virus adsorption capabilities when suspended in either wastewater, test cell percolate water, or distilled water containing divalent cations. The adsorptive capacity of Windsor and Charlton soils for poliovirus 1 and coliphage f2 increased greatly with the soil sample depth until leveling off at the midcore depths. Soil suspended in wastewater had the least virus adsorption capability for all depths studied.     

Fate of virus in wastewater applied to slow-infiltration land treatment systems.

The removal of seeded coliphage f2 and indigenous enteroviruses from primary and secondary wastewaters applied by spray irrigation to sandy loam and silt loam soils in field test cells was examined. The amount of f2 recovered from 170-cm-deep soil percolate samples taken over a 53-day period never exceeded 0.1% of applied virus levels and was usually below detection limits. Indigenous enterovirus levels in percolate waters also constituted only a small portion of those found in the wastewaters. At 10 days after seeding, f2 virus was present throughout the soil column but tended to accumulate around the soil core middepths. Coliphage f2 disappeared from the soil surface regions at a high rate, and by 53 days very little virus could be detected within the length of the soil columns. Sterilized soil core segments from different depths were studied to determine their virus adsorption capabilities when suspended in either wastewater, test cell percolate water, or distilled water containing divalent cations. The adsorptive capacity of Windsor and Charlton soils for poliovirus 1 and coliphage f2 increased greatly with the soil sample depth until leveling off at the midcore depths. Soil suspended in wastewater had the least virus adsorption capability for all depths studied.     

Engineering Pseudomonas putida KT2440 for simultaneous degradation of carbofuran and chlorpyrifos

Currently, chlorpyrifos (CP) and carbofuran are often applied together to control major agricultural pests in many developing countries, in most cases, they are simultaneously detected in agricultural soils. Some cost‐effective techniques are required for the remediation of combined pollution caused by multiple pesticides. In this work, we aim at constructing a detectable recombinant microorganism with the capacity to simultaneously degrade CP and carbofuran. To achieve this purpose, CP/carbofuran hydrolase genes and gfp were integrated into the chromosome of a biosafety strain Pseudomonas putida KT2440 using a chromosomal scarless modification strategy with upp as a counter‐selectable marker. The toxicity of the hydrolysis products was significantly lower compared with the parent compounds. The recombinant strain could utilize CP or carbofuran as the sole source of carbon for growth. The inoculation of the recombinant strain to soils treated with carbofuran and CP resulted in a higher degradation rate than in noninoculated soils. Introduced green fluorescent protein can be employed as a biomarker to track the recombinant strain during bioremediation. Therefore, the recombinant strain has potential to be applied for in situ bioremediation of soil co‐contaminated with carbofuran and CP.     

Fungicidal control of Rhizoctonia solani in relation to soil texture, organic matter and clay minerals

In pot tests, MEMC, quintozene, captafol, carboxin, thiabendazole, carbendazim, benomyl and thiophanate-methyl used as seed treatments gave much better control of cowpea seedling rot in light-textured sandy and loamy sand soils than in heavy-textured loam and silt loam soils inoculated with Rhizoctonia solani. Disease control by chloroneb was not altered by soil texture. Amendment of sandy soil with montmorillonite reduced disease control with all fungicides, except chloroneb and carboxin; similar amendments with kaolinite decreased efficacy of MEMC and captafol. Green manuring with cluster bean reduced disease control by MEMC, captafol, benomyl and thiophanate-methyl; sunnhemp reduced efficacy of MEMC. Most fungicides gave poor disease control when farm yard manure or biogas sludge was added to soil, the sludge having the more marked effect. All the fungicides tested, except carboxin, were inactivated to different extents by humic acid extracted from farm yard manure.     

Changes in organic carbon distribution with depth in agricultural soils in northern Belgium, 1960–2006

In most studies concerning the carbon (C) exchange between soil and atmosphere only the topsoil (0–0.3 m) is taken into account. However, it has been shown that important amounts of stable soil organic carbon (SOC) are also stored at greater depth. Here, we developed a quantitative model to estimate the evolution of the distribution of SOC with depth between 1960 (database 'Aardewerk') and 2006 in northern Belgium. This temporal analysis was conducted under different land use, texture and drainage conditions. The results indicate that intensified land management practices seriously affect the SOC status of the soil. The increase in plough depth and a change in crop rotation result in a significant decrease of C near the surface for dry silt loam cropland soils, (i.e. 1.02 ± 0.23 kg C m⁻² in the top 0.3 m between 1960 and 2006). In wet to extremely wet grasslands, topsoil SOC decreased significantly, indicating a negative influence of intensive soil drainage on SOC stock. This resulted in a decline of SOC between 1960 and 2006 in the top 1 m, ranging from 3.99 ± 2.57 kg C m⁻² in extremely wet silt loam soils to 2.04 ± 2.08 kg C m⁻² in wet sandy soils. A slight increase of SOC stock is observed under dry to moderately wet grasslands at greater depths corresponding to increased livestock densities in the region. The increase of SOC in the top 1 m under grassland ranges from 0.65 ± 1.39 kg C m⁻² in well drained silt loam soils to 2.59 ± 6.49 kg C m⁻² in moderately drained silt loam soils over entire period.     

荒漠区包气带土壤物理特征及其对地下水毛管上升影响的模拟

以巴丹吉林沙漠边缘荒漠区域为研究对象,选取两种典型的沙丘土壤剖面(沙壤土和砂土混合,均一砂土)进行土壤物理特征分析,并在此基础上模拟了不同土壤因素对毛管水上升过程的影响,探讨毛管水上升变化与土壤物理性质的关系,试图揭示地下水-毛管水-土壤水之间的相互作用过程.结果表明:研究区地下水毛管上升主要受土壤容重和土壤黏粒含量的影响,并且毛管水上升高度在地下潜水层以上为沙壤土的剖面中能够达到152 cm;地下潜水层以上为砂土的剖面中为120 cm.砂土中毛管水补给区域各土层水分分布更为均匀,并且从潜水面至地面方向土壤含水量呈递减趋势,沙壤土中毛管水补给区域土壤水分变异较大.借助Hydrus-3D模型能够较好模拟多因子影响下的土壤毛管水运动过程.潜水面以上土壤结构变化显著影响毛管水上升和剖面水分分布状况,但毛管水上升是否受季节性蒸发变化的影响以及毛管水与植物需水的关系有待进一步探究.     

Coloration changes of geologic media after addition of gasoline,diesel fuel,and ethylbenzene

The coloration changes of three soils (Amarillo sandy loam, Anthony sandy loam, and Oakville sandy loam) and two clays (kaolinite and montmorillonite) were monitored following the addition of four solvents (distilled water, unleaded gasoline, diesel fuel, and ethylbenzene) over a time period of 1 year. Soil and clay coloration was measured using Munsell color charts. In general, the Amarillo soil experienced the most extensive changes to a darker, grayer color. Initial color changes occurred in as little as 1 week, with subsequent changes occurring throughout the next 41 weeks. This study indicates that solvents can alter geologic media color and that the inferred chemical reduction processes can be an ongoing process.     

Transformation of urea and ammonium sulphate in different soils

Summary The transformation of urea and ammonium sulphate in Ladwa sandy loam and Balsamand sand was studied in laboratory. Urea took at least one week in sandy loam and 2 weeks in sandy soils to hydrolyse completely. The process of hydrolysis was faster in finer soil with high organic matter than in coarse soil having low organic matter. There was no nitrification upto 3 days in sandy loam and upto 7 days in sandy soils, respectively, but there was immobilization of NO₃-N during these initial periods. The NO₃-N content at the end of incubation period (35 days) was more in case of urea than in case of ammonium sulphate treated samples in sandy loam soil and reverse was true in sandy soil. The hydrolysis of urea did not follow zero or first order kinetics as proposed in previous studies.     

温度对不同粘粒含量稻田土壤有机碳矿化的影响

模拟了亚热带地区3种不同粘粒含量的水稻土(砂壤土、壤粘土、粉粘土)在5种温度(10、15、20、25和30℃)下的有机碳(SOC)矿化特征,分析SOC矿化对温度变化的响应.结果表明:在160d的培养期内,温度对3种水稻土SOC矿化量的影响有一定差异,30℃时砂壤土、壤粘土和粉粘土SOC矿化量分别是10℃时的3.5、5.2和4.7倍.在较低温度(≤20℃)下,SOC矿化速度较低且相对稳定;在较高温度(≥25℃)下,前期SOC矿化速度较高,随着培养时间的延长逐渐降低,并趋于稳定.3种水稻土SOC矿化的温度系数(Q10)随培养时间出现波动,砂壤土的Q10平均值最低,为1.92,壤粘土和粉粘土的Q10平均值较接近,分别为2.37和2.32;3种土壤矿化速率常数(k)与温度呈极显著的指数相关(P<0.01).3种水稻土有机碳矿化对温度变化的响应敏感度依次为壤粘土>粉粘土>砂壤土.     

Population Increase of Pratylenchus hexincisus on Corn as Related to Soil Temperature and Type

Population increase of Pratylenchus hexincisus on corn was tested over 3 months at 15, 20, 25, and 30 C in Marshall silt loam, Clarion silt loam, Buckner coarse sand, and Haig silty clay loam soils. The optimum temperature for increase was 30 C in all soils. The nematode population was significantly larger in Buckner coarse sand than in other soil types at 50 C. The recovered P. hexincisus populations equaled or exceeded initial inoculum levels at the two higher temperatures in Marshall silt loam and Haig silty clay loam and at 30 C in Clarion silt loam and Buckner coarse sand. P. hexincisus required 32,400 heat units in Haig silty clay loam and more than 40,000 heat units in the three other soil types to reach a level that is known to cause significant height and biomass reduction in corn under controlled condition.     

Soil types with different texture affects development of Rhizoctonia root rot of wheat seedlings

The effect of different soil textures, sandy (97.5% sand, 1.6% silt, 0.9% clay), loamy sand (77% sand, 11% silt, 12% clay) and a sandy clay loam (69% sand, 7% silt, 24% clay), on root rot of wheat caused by Rhizoctonia solani Kühn Anastomosis Group (AG) 8 was studied under glasshouse conditions. The reduction in root and shoot biomass following inoculation with AG-8 was greater in sand than in loamy sand or sandy clay loam. Dry root weight of wheat in the sand, loamy sand and sandy clay loam soils infested with AG-8 was 91%, 55% and 28% less than in control uninfested soils. There was greater moisture retention in the loamy sand and sandy clay loam soils as compared to the sand in the upper 10–20 cm. Root penetration resistance was greater in loamy sand and sandy clay loam than in sand. Root growth in the uninfested soil column was faster in the sand than in the loamy sand and sandy clay loam soils, the roots in the sandy soil being thinner than in the other two soils. Radial spread of the pathogen in these soils in seedling trays was twice as fast in the sand in comparison to the loamy sand which in turn was more than twice that in the sandy clay loam soil. There was no evidence that differences among soils in pathogenicity or soil spread of the pathogen was related to their nutrient status. This behaviour may be related to the severity of the disease in fields with sandy soils as compared to those with loam or clay soils. This revised version was published online in June 2006 with corrections to the Cover Date.     

Growth and survival of cowpea rhizobia in bauxitic silt loam and sandy clay loam soils

Survival of 4 cowpea Rhizobium strains, IRC291, MI-50A, JRW3 and JRC29, in two soil types (bauxitic silt loam and sandy clay loam) undergoing drying at 30°C and 37°C was examined. While all strains except JRW3 showed a general pattern of increase in their numbers during the first 3 weeks in sterile soils, none of the strains showed any increase in their population in non-sterile soils. Cowpea rhizobia showed better survival in non-sterile bauxitic silt loam than in clay loam soils at 30°C. However, the long-term survival (examined up to 6 months) of rhizobia in both soils was poor at 37°C as compared to 30°C. We also found that cowpea rhizobia survived better in soils undergoing drying than in moist soils at 30°C. Our results suggest that (a) cowpea rhizobia survived better in bauxitic silt loam than in clay loam soil and (b) the low indigenous cowpea rhizobial population in Jamaican soils may be due to their poor long-term survival and weak saprophytic competence.     

Surfactant mediated enhanced biodegradation of hexachlorocyclohexane (HCH) isomers by Sphingomonas sp. NM05

Environmental biodegradation of several chlorinated pesticides is limited by their low solubility and sorption to soil surfaces. To mitigate this problem we quantified the effect of three biosurfactant viz., rhamnolipid, sophorolipid and trehalose-containing lipid on the dissolution, bioavailability, and biodegradation of HCH-isomers in liquid culture and in contaminated soil. The effect of biosurfactants was evaluated through the critical micelle concentration (CMC) value as determined for each isomer. The surfactant increased the solubilization of HCH isomers by 3-9 folds with rhamnolipid and sophorolipid being more effective and showing maximum solubilization of HCH isomers at 40 μg/mL, compared to trehalose-containing lipid showing peak solubilization at 60 μg/mL. The degradation of HCH isomers by Sphingomonas sp. NM05 in surfactant-amended liquid mineral salts medium showed 30% enhancement in 2 days as compared to degradation in 10 days in the absence of surfactant. HCH-spiked soil slurry incubated with surfactant also showed around 30-50% enhanced degradation of HCH which was comparable to the corresponding batch culture experiments. Among the three surfactants, sophorolipid offered highest solubilization and enhanced degradation of HCH isomers both in liquid medium and soil culture. The results of this study suggest the effectiveness of surfactants in improving HCH degradation by increased bioaccessibility.