Nitrate reductase, arginine deaminase, urease and dehydrogenase activities in natural soil (ridges with forest) and in cotton soil after acetamiprid treatments

Soil enzymes are indicators of microbial activities in soil and are often considered as an indicator of soil health and fertility. They are very sensitive to the agricultural practices, pH of the soil, nutrients, inhibitors and weather conditions. To understand the effect of an insecticide, acetamiprid (IUPAC Name: (E)-N1-[(6-chloro-3-pyridyl) methyl]-N2-cyano-N1-methyl acetamidine) on different soil enzyme activities, the experiments were conducted for three consecutive years (2003--2005) at control and cotton experimental fields of Indian Agricultural Research Institute (IARI) and natural area (ridges with forest) in Delhi. The combined results for all three years were presented here to understand the impact of acetamiprid on soil enzyme activities. Acetamiprid was applied three times in one crop season after 41, 48 and 73 days of sowing, to control the pest. Soil of treated fields was analyzed for insecticide residues immediately after first insecticide treatment and thereafter at definite period. The residues of acetamiprid in experimental soil was varied from 0.30+/-0.13 to 22.67+/-0.2 microg g(-1)d.wt. soil, during the crop period of 2003. The insecticide residues for 2004 ranged between 0.59+/-0.38 and 13.42+/-0.71 microg g(-1)d.wt. soil and for 2005 it ranged between 0.48+/-0.22 and 19.81+/-0.33 microg g(-1)d.wt. soil. An average half life of acetamiprid in our treated field was 11.2+/-1.7 days for all three years. Similarly, the soil from natural area and control were also tested for insecticide residues. No detectable insecticide residues had been found. Soil from three localities i.e. natural, control and experimental fields were tested for different enzyme activities. Nitrate reductase, arginine deaminase, urease and dehydrogenase activities were high in natural soil in comparison to control soil and insecticide treated soil in all three experimental years. At the same time, nitrate reductase activity was all time low in acetamiprid treated soil. Acetamiprid had inhibitory effects on nitrate reductase, arginine deaminase and urease activities. After first treatment (43 days after crop sowing), nitrate reductase (41%), arginine deaminase (22%) and urease (35%) activities were declined. Dehydrogenase activity increased to 22% after first insecticide application. Enzyme activities were recovered at the end of each crop season. Therefore, it can be attributed that agricultural practices, weather conditions and use of acetamiprid might be responsible for the different level of enzyme activities in soil.     

Occurrence and distribution of hexachlorocyclohexane isomers in vegetation samples from a contaminated area

The occurrence and distribution of four major hexachlorocyclohexane (HCH) isomers (alpha-, beta-, gamma- and delta-) were studied in vegetation samples of a highly contaminated area close to a small-scale industrial belt in Lucknow (North India). Eight species of plants were collected at different points of the contaminated area and different parts of the plants were separated in order to study the difference in uptake and accumulation. The samples were extracted by matrix solid-phase dispersion (MSPD) extraction and finally determined by a gas-chromatograph equipped with (63)Ni electron capture detector (ECD). HCH isomers were present in almost all samples and the concentration of total HCH in the plant sample analyzed varied between 13 and 44 mg kg(-1), being the main isomer of beta-HCH (8-22 mg kg(-1)). Lindane (gamma-HCH) was present in all samples (1-9 mg kg(-1)). Solanum torvum Sw., and Erianthus munja shows the highest and lowest capacity for accumulation of HCH, respectively with a significant difference at p<0.01 level. The highest concentration of HCH residue in root samples indicates the most likely mechanism of HCH accumulation in these plants was sorption of soil HCH on roots. Solanum torvum Sw., and Withania somnifera (L.) Dunal could accumulate considerable levels of HCH isomers (44 and 34 mg kg(-1), respectively). The results reflect the importance of plants in monitoring purposes and their potential for phytoremediation of HCH contaminated soils.     

Influence of plant growth promoting bacteria and its mutant on heavy metal toxicity in Brassica juncea grown in fly ash amended soil

In this study a metal tolerant plant growth promoting bacteria, NBRI K28 Enterobacter sp. was isolated from fly ash (FA) contaminated soils. The strain NBRI K28 and its siderophore overproducing mutant NBRI K28 SD1 were found capable of stimulating plant biomass and enhance phytoextraction of metals (Ni, Zn and Cr) from FA by metal accumulating plant i.e. Brassica juncea (Indian mustard). Concurrent production of siderophores, Indole acetic acid (IAA) and phosphate solubilization revealed its plant growth promotion potential. The strain also exhibited 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity. In most of the cases mutant of NBRI K28, exerted more pronounced effect on metal accumulation and growth performance of B. juncea plants than wild type.     

Effect of UV radiation and temperature on mineralization and volatilization of coumaphos in water

This study was undertaken to determine the dissipation and degradation of coumaphos [O-(3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7-yl) O,O-diethyl phosphorothioate] under different sunlight conditions and at different temperatures. The effect of the ultra violet (UV) component of solar radiation was also studied using quartz tubes in addition to other radiation in the visible range using glass tubes and the results were compared with those obtained under the dark light conditions. Water suspensions of coumaphos were incubated at three temperatures viz. 22 degrees C, 37 degrees C and 53 degrees C in closed systems to study the effect of temperature. Volatilization, mineralization and degradation of coumaphos increased with an increase in temperature and exposure to solar radiation, particularly under the UV component of the solar radiation. Major loss of the pesticide occurred through volatilization. The optimum temperature for the degradation of coumaphos was found to be at 37 degrees C. The data obtained from the mineralization and degradation studies indicated that 53 degrees C crosses the biological range for suitable growth of microorganism. UV radiation exposure along with maintaining temperature at 37 degrees C may prove useful in the dissipation and/or degradation of coumaphos prior to its disposal as waste from cattle dipping vats.     

House fly (Musca domestica): a review of control strategies for a challenging pest

Musca domestica L. (Diptera: Muscidae), commonly called the house fly, is a major domestic, medical and veterinary pest that causes irritation, spoils food and acts as a vector for many pathogenic organisms. In this paper, the social and health problems related to housefly are introduced with the associated need to control its population. Physical and chemical methods of house fly control are briefly discussed. The main focus of this review is on the biological control methods for house fly control, that comprise botanical, fungal, bacterial and parasitoid agents. Although several biocontrol agents are still in the nascent stage, some of them (especially fungal and parasitoid agents) have shown reliable field performance and seem to be suitable candidates for commercialization. However, the majority of these laboratory and field studies have been conducted in the temperate region. It remains to be seen whether the application of biocontrol agents would be feasible in tropical environments. The integrated pest management practices, which can provide more reliable field performance, have also been discussed. A multi-dimensional approach that exerts control on all the life stages of house fly, but simultaneously preserves the fly's natural enemies could be an ecologically sustainable way of maintaining the fly populations below maximally acceptable limits.     

The effect of temperature on PAHs emission from incineration of acrylic waste

Incineration of acrylic waste solution in a lab scale quartz tube vertical incinerator showed the presence of 12–15 polycyclic aromatic hydrocarbons (PAHs) from a list of 16 priority pollutants at 700–1100^˚C after an interval of 50^˚C. The amount of total 16 PAHs at 900 and 1100^˚C was about 8.5 and 1.25 times higher than those at 700^˚C (739.48 μg g⁻¹) respectively. The amount of total probable (2A) and possible (2B) human carcinogenic PAHs was minimum at 700^˚C.     

Zn、Cd单一及复合污染对黑麦草根分泌物及根际Zn、Cd形态的影响

采用根袋土培试验,研究了锌、镉单一及复合污染对重金属富集植物黑麦草生长、锌镉积累、根分泌物及根际Zn、Cd形态的影响.结果表明,锌镉共存下(8 mmol/kg Zn+2 mmol/kg Cd),黑麦草对锌、镉的吸收为协同效应;仅镉污染时(2 mmol/kg Cd),镉对植株吸收锌为抑制效应.黑麦草吸收的锌、镉主要集中在地上部,以锌、镉复合污染时植株地上部对锌、镉的富集量最大,分别达到3 108.72、73.97 mg/kg,具有作为土壤重金属锌、镉污染植物修复材料的潜力.根际的松结合态锌、镉（交换态、碳酸盐结合态和铁锰结合态）含量大于其非根际的松结合态锌、镉含量.Cd污染和Zn、Cd复合污染的根际和非根际土壤镉形态均以交换态>碳酸盐结合态>铁锰结合态>残渣态>有机结合态.Zn污染及Zn、Cd复合污染根际和非根际土壤各锌形态以铁锰结合态>碳酸盐结合态>残渣态>有机结合态>交换态,而Cd污染的根际和非根际的锌形态则以残渣态>铁锰结合态>有机结合态>碳酸盐结合态>交换态.Zn、Cd污染促进了黑麦草根系氨基酸的分泌,降低了根际土壤的pH值,以Zn、Cd复合污染根际土壤氨基酸总量最大,分别为对照、Zn和Cd污染的1.95、1.54和1.40倍,根际土壤的pH值最低(5.18).根际氨基酸含量在重金属胁迫下明显增加,可能与黑麦草适应重金属胁迫有关.根际pH值高于非根际是根际Zn、Cd有效性大于非根际的重要原因.     

Allelopathic response of <Emphasis Type="Italic">Vetiveria zizanioides</Emphasis> (L.) Nash on members of the family Enterobacteriaceae and <Emphasis Type="Italic">Pseudomonas</Emphasis> spp.

The biological removal of phosphates was carried as a part of treatment strategy. Vetiveria zizanioides (L.) Nash belonging to the family Poaceae was used for biological removal of biostimulants. Vetiver reportedly has mycorrhizal association; besides having potential for removal of PO₄ ⁻³ also showed allelopathic affect on the microorganisms present in the water. In fact after a period of 96 h old roots of this plant have been found to have killing effects on the E. coli, Enterobacter spp. Pseudomonas spp. belonging to the family Enterobacteriaceae. The paper is opening a new face of study.     

Amelioration of Indian urban air pollution phytotoxicity in Beta vulgaris L. by modifying NPK nutrients

Air pollution levels are increasing at an alarming rate in many developing countries, including India and causing a potential threat to crop production. Field experiments were conducted to examine the impact of urban air pollutants on biomass (yield) and some physiological and biochemical parameters of palak (Beta vulgaris L. var. All Green) that grew from germination to maturity at seven periurban sites of Allahabad city having different concentrations of air pollutants under different levels of nutrients. The 6h daily mean NO2, SO2 and O3 concentrations varied from 2.5 to 42.5, 10.6 to 65 and 3.5 to 30.8 microg m(-3), respectively at different locations. Levels of air pollution showed significant negative correlations with photosynthetic pigments, protein, ascorbic acid and starch contents and catalase activity of palak leaves. A significant negative correlation was found for total biomass with SO2 (r=-0.92), NO2 (r=-0.85) and O3 (r=-0.91) concentrations. The increased fertilizer application (N, P and K) over the recommended dose resulted in a positive response by reducing losses in photosynthetic pigments and total biomass. This study proved that ambient air pollution of Allahabad city is influencing negatively to the growth and yield of palak plants.     

The Potential of Soil Carbon Sequestration Through Improved Management Practices in Norway

The study was conducted to assess the potential of Norwegian agricultural ecosystems to sequester carbon (C) based on the data from some long-term agronomic and land use experiments. The total emission of CO₂ in Norway in 1998 was 41.4 million metric ton (MMT), of which agriculture contributed only 0.157 MMT, or <0.4% of the total emissions. With regards to methane (CH₄) and nitrous oxide (N₂O) gases, however, agricultural activities contributed 32.5% and 51.3% of their respective emissions in Norway. The soil organic carbon (SOC) losses associated with accelerated soil erosion in Norway are estimated at 0.475 MMTC yr^–1. Land use changes and soil/crop management practices with potential for SOC sequestration include conservation tillage methods, judicious use of fertilizers and manures, use of crop residues, diverse crop rotations, and erosion control measures. The potential for SOC sequestration is 0.146 MMTC yr^–1 for adopting conservation tillage, 0.011–0.035 MMTC yr^–1 for crop residue management, 0.026 MMTC yr^–1 for judicious use of mineral fertilizer, 0.016–0.135 MMTC yr^–1 for manure application, and 0.036 MMTC yr^–1 for adopting crop rotations. The overall potential of these practices for SOC sequestration ranges from 0.591 to 1.022 MMTC yr^–1 with an average value of 0.806 MMTC yr^–1. Of the total potential, 59% is due to adoption of erosion control measures, 5.8% to restoration of peat lands, 21% to conversion to conservation tillage and residue management, and 14% to adoption of improved cropping systems. Enhancing SOC sequestration and improving soil quality, through adoption of judicious land use and improved system of soil and crop management, are prudent strategies for sustainable management of soil, water and environment resources.Readers should send their comments on this paper to: bhaskarn ath@aol.com within 3 months of publication of this issue.