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81.
82.
Nitrate (NO3-) pollution of surface and subsurface waters has become a major problem in agricultural ecosystems. Field trials were conducted from 1996 to 1998 at St-Emmanuel, Quebec, Canada, to investigate the combined effects of water table management (WTM) and nitrogen (N) fertilization on soil NO3- level, denitrification rate, and corn (Zea mays L.) grain yield. Treatments consisted of a combination of two water table treatments: free drainage (FD) with open drains at a 1.0-m depth from the soil surface and subirrigation (SI) with a design water table of 0.6 m below the soil surface, and two N fertilizer (ammonium nitrate) rates: 120 kg N ha(-1) (N120) and 200 kg N ha(-1) (N200). Compared with FD, SI reduced NO3(-)-N concentrations in the soil profile by 37% in spring 1997 and 2% in spring 1998; and by 45% in fall 1997 and 19% in fall 1998 (1 mg NO3(-)-N L(-1) equals approximately 4.43 mg NO3- L(-1)). The higher rate of N fertilization resulted in greater levels of NO3(-)-N in the soil solution. Denitrification rates were higher in SI than in FD plots, but were unaffected by N rate. The N200 rate produced higher yields than N120 in 1996 and 1997, but not 1998. Corn yields in SI plots were 7% higher than FD plots in 1996 and 3% higher in 1997, but 25% lower in 1998 because the SI system was unable to drain the unusually heavy June rains, resulting in waterlogging. These findings suggest that SI can be used as an economical means of reducing NO3- pollution without compromising crop yields during normal growing seasons.  相似文献   
83.
Distinct morphophysiological variations observed for over 2 years with-in short distances among four perennial plants indicated genetic diversity among the lines growing at three places. The isozyme and SDS polyacrylamide gel banding patterns as genetic markers were used to investigate four perennial species, namely Dalbergia sissoo Roxb., Delonix regia (Boj.) Refin., Cassia fistula L. and Calotropis procera R. Br. Plant materials collected from three locations (Agra, Gwalior and Lucknow) differing in climo-edaphic variables were examined for 4 enzyme systems, viz., esterase, polyphenol oxidase, peroxidase and superoxide dismutase (EST, PPO, PRX and SOD). Among the four isozymes SOD and PRX revealed best discriminating power. Protein banding patterns as well as zymogram revealed that Dalbergia sissoo growing at Gwalior was closer to that of Agra; Delonix regia depicted highest similarity between Lucknow and Agra and Calotropis procera of Lucknow location was more closer to Gwalior than Agra. The results confirm genetic diversity in the species as a means of adaptation to differing climo-edaphic variables.  相似文献   
84.
85.
An experiment has been conducted under laboratory conditions to investigate the effect of decomposition of two edible oil cakes, viz. mustard cake (Brassica juncea L) and groundnut cake (Arachis hypogaea L), and two non-edible oil cakes, viz. mahua cake (Madhuca indica Gmel) and neem cake (Azadirachta indica Juss), at the rate of 5.0 t ha?1 on the changes of microbial growth and activities in relation to transformations and availability of some plant nutrients in the Gangetic alluvial (Typic Haplustept) soil of West Bengal, India. Incorporation of oil cakes, in general, highly induced the proliferation of total bacteria, actinomycetes, and fungi, resulting in greater retention and availability of oxidizable C, N, and P in soil. As compared to untreated control, the highest stimulation of total bacteria and actinomycetes was recorded with mustard cake (111.9 and 84.3 %, respectively) followed by groundnut cake (50.5 and 52.4 %, respectively), while the fungal colonies were highly accentuated due to the incorporation of neem cake (102.8 %) in soil. The retention of oxidizable organic C was highly increased due to decomposition of non-edible oil cakes, more so under mahua cake (14.5 %), whereas edible oil cakes and groundnut cake in particular exerted maximum stimulation (16.7 %) towards the retention of total N in soil. A similar trend was recorded towards the accumulation of available mineral N in soil and this was more pronounced with mustard cake (45.6 %) for exchangeable NH4 + and with groundnut cake (63.9 %) for soluble NO3 ?. The highest retention of total P (46.9 %) was manifested by the soil when it was incorporated with neem cake followed by the edible oil cakes; while the available P was highly induced due to the addition of edible oil cakes, the highest being under groundnut cake (23.5 %) followed by mustard cake (19.6 %).  相似文献   
86.
An experiment was conducted under laboratory conditions to investigate the effect of two systemic herbicides, viz. pendimethalin (a dinitroaniline) and quizalofop (an arylphenoxy propionic acid) at their recommended field application rates (1.0?kg and 50?g active ingredient per hectare, respectively), either separately or in a combination, on growth and activities of phosphate-solubilizing microorganisms in relation to their effects on biochemical transformations and availability of organic carbon, total and available phosphorus in a Typic Haplustept soil of West Bengal, India. Application of herbicides, in general, significantly stimulated the growth and activities of phosphate-solubilizing microorganisms which increased microbial biomass resulting in higher accumulation of oxidizable organic carbon, total and available phosphorus in soil as compared to untreated control. The combined application of both the herbicides highly stimulated the proliferations of phosphate-solubilizing microorganisms, while pendimethalin alone significantly accentuated phosphate-solubilizing capacities 36.4% as compared to untreated control and retained highest amount of total phosphorus due to greater microbial activities in soil. The separate application of quizalofop also manifested an induced effect on the proliferations of phosphate-solubilizing microorganisms and accounted significant amounts of organic carbon and available phosphorus in the soil system. The results of the present study thus indicated that the cited herbicides at their field application rates can be safely used to eradicate weeds in the crop fields.  相似文献   
87.
In relation to fluoride in ground water, dental fluorosis is studied in seven villages, viz., Nasipur, Vabanandapur, and Deshnabagram under Nalhati I block and Kamdebpur, Chalk Atla, Nowapara, and Junitpur under Rampurhat II block, of Birbhum district, West Bengal, India. Water samples (N = 70) were collected from the tube wells of the mentioned villages in the months of December 2010 to February 2011 and analyzed for fluoride and other water parameters. The study result revealed that the fluoride levels of almost all the water samples (95.7%) were higher than 1.5 mg/L, with mean values of 3.15 and 3.83 mg/L in Nalhati I block and Rampurhat II block, respectively. Dental fluorosis of 490 respondents was visually determined by a competent dentist using Dean’s index (DI) and the tooth surface index of fluorosis (TSIF). According to the DI, the percentage of severely affected respondents was lowest in Chalk Atla (0%) and highest in Deshnabagram (50%). The percentage of severely affected respondents was lowest in Kamdebpur and Chalk Atla (0%) and highest in Nowapara (20%) according to the TSIF score. The age group 10–20 years showed the highest percentage of severe DI (40.8%) and the age group 21–30 years showed the highest percentage of severe TSIF (22.51%) compared to the other age groups in the study. The positive relationship between the fluoride level in water and the severity of dental fluorosis has been proved statistically. The high mean score of dental fluorosis indicates that dental fluorosis is endemic throughout the study area.  相似文献   
88.
89.
Isoproturon (IPU)-degrading soil bacteria were isolated from herbicide-applied wheat fields. These isolates were identified using cultural, morphological, biochemical and 16S rRNA sequencing methods. 16S rRNA sequences of both the bacterial isolates were compared with NCBI GenBank data base and identified as Bacillus pumilus and Pseudoxanthomonas sp. A soil microcosm study was carried out for 40 days in six different treatments. Experimental results revealed maximum 95.98% IPU degradation in treatment 6 where bacterial consortia were augmented in natural soil, followed by 91.53% in treatment 5 enriched with organic manure as an additional carbon source. However, only 14.03% IPU was degraded in treatment 1 (control) after 40 days. In treatments (2–4), 75.59%, 70.92% and 77.32% IPU degradation was recorded, respectively. IPU degradation in all the treatments varied significantly over the control. 4-Isopropylaniline was detected as IPU degradation by-product in the medium. The study confirmed that B. pumilus and Pseudoxanthomonas sp. performed effectively in soil microcosms and could be employed profitably for field-scale bioremediation experiments.  相似文献   
90.
Surface ozone is mainly produced by photochemical reactions involving various anthropogenic pollutants, whose emissions are increasing rapidly in India due to fast-growing anthropogenic activities. This study estimates the losses of wheat and rice crop yields using surface ozone observations from a group of 17 sites, for the first time, covering different parts of India. We used the mean ozone for 7 h during the day (M7) and accumulated ozone over a threshold of 40 ppbv (AOT40) metrics for the calculation of crop losses for the northern, eastern, western and southern regions of India. Our estimates show the highest annual loss of wheat (about 9 million ton) in the northern India, one of the most polluted regions in India, and that of rice (about 2.6 million ton) in the eastern region. The total all India annual loss of 4.0–14.2 million ton (4.2–15.0%) for wheat and 0.3–6.7 million ton (0.3–6.3%) for rice are estimated. The results show lower crop loss for rice than that of wheat mainly due to lower surface ozone levels during the cropping season after the Indian summer monsoon. These estimates based on a network of observation sites show lower losses than earlier estimates based on limited observations and much lower losses compared to global model estimates. However, these losses are slightly higher compared to a regional model estimate. Further, the results show large differences in the loss rates of both the two crops using the M7 and AOT40 metrics. This study also confirms that AOT40 cannot be fit with a linear relation over the Indian region and suggests for the need of new metrics that are based on factors suitable for this region.  相似文献   
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