Nitrogen and phosphorus limitations of microbial respiration in a tropical phosphorus-fixing acrisol (ultisol) compared with organic compost     

Ulrik Ilstedt  Sarabpreet Singh 《Soil biology & biochemistry》2005,37(7):1407-1410

We studied the nutrient limitations of microbial respiration over time after the addition of glucose (G), glucose+nitrogen (G+N) or glucose+phosphorus (G+P) to a phosphorus-fixing tropical acrisol down to a depth of 80 cm, compared with those from compost. In the acrisol, the initial rate of respiration increase was higher when P was added together with glucose than when P was excluded. Without N, respiration reached a plateau faster and at a lower level than when N was added in excess. With glucose alone, the respiration kinetics followed the lower of the curves with G+N or G+P at any given time. Thus, nitrogen limited the maximum level of microbial respiration in the acrisol if ample carbon was available, but the initial respiration rate was limited by phosphorus. In contrast, for compost respiration was always lowest when N was not added. In conclusion, microbial respiration depended on the P-fixing properties of the soil, the time scale and the carbon availability.  相似文献   

Supercritical fluid extraction of lycopene from tomato processing byproducts   总被引：15，自引：0，他引：15  

Rozzi NL  Singh RK  Vierling RA  Watkins BA 《Journal of agricultural and food chemistry》2002,50(9):2638-2643

Tomato seeds and skins acquired from the byproduct of a local tomato processing facility were studied for supercritical fluid extraction (SFE) of phytochemicals. The extracts were analyzed for lycopene, beta-carotene, alpha-carotene, alpha-tocopherol, gamma-tocopherol, and delta-tocopherol content using high-performance liquid chromatography-electrochemical detection and compared to a chemically extracted control. SFEs were carried out using CO(2) at seven temperatures (32-86 degrees C) and six pressures (13.78-48.26 MPa). The effect of CO(2) flow rate and volume also was investigated. The results indicated that the percentage of lycopene extracted increased with elevated temperature and pressure until a maximum recovery of 38.8% was reached at 86 degrees C and 34.47 MPa, after which the amount of lycopene extracted decreased. Conditions for the optimum extraction of lycopene from 3 g of raw material were determined to be 86 degrees C, 34.47 MPa, and 500 mL of CO(2) at a flow rate of 2.5 mL/min. These conditions resulted in the extraction of 61.0% of the lycopene (7.19 microg lycopene/g).  相似文献   

AFLP Analysis of the Phenetic Organization and Genetic Diversity in the Sugarcane Complex, Saccharum and Erianthus     

A. Selvi  N. V. Nair  J. L. Noyer  N. K. Singh  N. Balasundaram  K. C. Bansal  K. R. Koundal  T. Mohapatra 《Genetic Resources and Crop Evolution》2006,53(4):831-842

Amplified fragment length polymorphism (AFLP) markers were evaluated for determining the phylogenetic relationships, and the diversity in the Saccharum complex using 30 clones belonging to S. officinarum, S. robustum, S. spontaneum, S. barberi, S. sinense and the related genus Erianthus. The phenetic tree of the species clones based on AFLP data was consistent with the known taxonomical relationships. AFLP gave higher resolution of closely related species into discrete groups than that by RAPD and RFLP markers, reported earlier. The levels of diversity within the various Saccharum species were also found to be higher than those obtained previously with the same set of clones using RAPD markers. The intraspecies similarity in S. barberi and S. sinense was much higher than interspecies similarity suggesting a clear separation of the two, which are considered ‘horticultural species’. The genetic similarity matrix derived from a single primer combination highly correlated (r = 0.980) with that obtained from all the 12 primer combination used in the study, thus highlighting the efficiency of a single primer combination in delineating species relationships. All the primer combinations could identify markers that are specific to each of the species and the genus Erianthus. Among the species, specific markers were highest in S. spontaneum followed by S. robustum, S. barberi, S. officinarum and S. sinense. Erianthus had a distinct profile with 30% of the total amplified fragments being specific to it. This offers great scope for identifying intergeneric hybrids, which has been very difficult using morphological traits and RAPD markers. High degree of correspondence between the results from the cluster analysis based on Jaccard's similarity index, Neighbour Joining tree based on Sokal and Michener distance matrix and AFTD (Analyses Factorielle on Table of Distances) analysis clearly demonstrated that AFLP markers would be an appropriate tool in providing better information about the relationships among the species, estimation of diversity, and in revealing species and genus specific markers that could be directly applied in sugarcane breeding programmes.  相似文献   

Mercury pollution of effluent,air, and soil near a battery factory in Tanzania     

E. Semu  B. R. Singh  A. R. Selmer-Olsen 《Water, air, and soil pollution》1986,27(1-2):141-146

Effluent, air, and soil samples near a battery factory in Dar es Salaam, Tanzania, where HgCl₂ is used to prevent mold growth, were collected to explore the potential for pollution of the environment from industrial discharge of Hg. Flameless atomic absorption spectrophotometry was used for Hg determinations. The concentration of Hg in the effluent ranged from <0.2 to 5.2 mg L^?1 and the Hg concentration varied greatly within and among sampling days, showing different peaks. Air contained a mean of 4.0 μg m^?3 with little variation within and between sampling days. Soils near the factory contained high Hg levels, from 6.7 to 472 mg kg^?1 in the immediate vicinity, the highest level being associated with disposal of solid waste (defective batteries). Downwind the concentration of Hg decreased with increasing distance from the factory resulting in a soil concentration of 1.0 mg Hg kg^?1 about 2 km away. Upwind the Hg concentration decreased drastically within a distance of 100 to 200 m.  相似文献   

Nutrient immobilization and release patterns during plant decomposition in a dry tropical bamboo savanna,India   总被引：3，自引：0，他引：3  

S. K. Tripathi  K. P. Singh 《Biology and Fertility of Soils》1992,14(3):191-199

Summary Decomposition and changes in nutrient content of six litter types (leaves, sheaths, roots, twigs, and wood of bamboo, and grass shoots) were studied in nylon net bags for 2 years. The annual weight loss was (% of initial) bamboo leaves 56.5, bamboo sheaths 79.5, bamboo roots 65.8, bamboo twigs 49.6, bamboo wood 31.2, and grass shoots 74.9. Elemental mobility followed the order K>Na>C>P>Ca>N in all components except wood. Generally, an initial increase was followed by a consistent decrease in the contents of N (leaves), P (leaves, roots, wood) and Ca (leaves, roots, grass), and Na (wood). Most of the nutrients were immobilized in the rainy season. C and K contents showed a constant decrease throughout the decomposition period. Materials with a greater C:N ratio (>50) tended to accumulate more nutrients and retain them for longer, except for the bamboo twigs. The critical C:N ratio (at which a net release of N occured) for the leaf material was 25. Litter components with more initial N (sheaths) showed greater weight loss than those with less N (leaves, twigs, and wood). Overall, N and P were lost at the slowest rates while C and K were lost at faster rates. Initial lignin, lignin: N, C:N and C concentrations had a better predictive value for annual weight loss and nutrient release in bivariate relationships. A combination of the initial lignin value and the C: N ratio explained 93% of the variation in annual weight loss. A significant relationship was also observed between the annual weight loss rate and the nutrient mineralization/release rate.  相似文献   

Effects of solar treatment on germination of sclerotia (Sclerotium rolfsii Sacc.) and on other soil mycoflora     

R. K. Singh  R. P. Shukla  R. S. Dwivedi 《Biology and Fertility of Soils》1990,10(2):152-154

Summary Only 10% of sclerotia germinated in a tarpcovered plot after 45 days of treatment while 50% of sclerotia germinated in the control plot. However, complete inhibition of sclerotia germination was not achieved. The maximum temperature recorded was 53°C, after 45 days of treatment in a tarped plot at 1 cm depth. The incidence of Acrophialophora fusispora, Aspergillus spp., Spicaria sp., and Trichoderma viride increased in soil after 45 days of the solar treatment.  相似文献   

Optimisation of Design and Operational Parameters of a Pneumatic Seed Metering Device for Planting Cottonseeds   总被引：2，自引：0，他引：2  

R.C. Singh  G. Singh  D.C. Saraswat 《Biosystems Engineering》2005,92(4):3753

  相似文献   

Synthesis and fungicidal activity of novel 4,4'-bis(2' '-aryl-5' '-methyl/unsubstituted-4' '-oxo-thiazolidin-3' '-yl) bibenzyl     

Siddiqui IR  Singh PK  Singh J  Singh J 《Journal of agricultural and food chemistry》2003,51(24):7062-7065

Reduction followed by nitration of benzil I yielded 4,4'-dinitrobibenzyl (III) which by reduction furnished quantitatively and analytically pure 4,4'-diaminobibenzyl (IV) which on condensation with different carbonyl compounds gave 4,4'-bis (benzylideneamino) bibenzyls (Va-f). Compounds (Va-f) on cycloaddition with mercaptoacetic acid/2-mercaptopropionic acid yielded the corresponding 4-oxothiazolidin-3-yl bibenzyls (VIa-l). The compounds VIg-l have two chiral centers in each thiazolidinone moiety so two diastereomers are possible, but on crystallization and repeated chromatography, one diastereomer was obtained. The absolute configuration of the diastereomer was tentatively assigned on the basis of (1)H NMR spectra. (1)H NMR spectra of the product showed a distinct doublet at delta 1.22 for C(5)-CH(3) of thiazolidinone ring (22, 23) and a distinct quartet at delta 4.20 for the C(5)-H proton. Similarly, the C(2) proton showed an independent singlet at delta 5.95, so the diastereomers obtained were assigned trans configuration. Compounds Va-f and VIa-l were evaluated in vitro for their fungitoxicities against Fusarium oxysporium and Penicillium citrinum. All the compounds were found to be antifungal active. Some of the compounds displayed activities comparable with that of the commercial fungicide Dithane M-45. Structure-activity relationships for the screened compounds are discussed.  相似文献   

<Emphasis Type="Italic">Azolla</Emphasis> sporulation in response to application of some selected auxins and their combination with gibberellic acid     

P. Kar  S. Mishra  D. Singh 《Biology and Fertility of Soils》2002,35(5):314-319

  相似文献   

Modeling yield sustainability for different rotations in long-term barley trials     

Murari Singh  Michael J. Jones 《Journal of Agricultural, Biological & Environmental Statistics》2002,7(4):525-535

In crop rotation trials, the errors arising over time on the same plot are correlated. Often-used analyses assume zero or constant correlation between the errors while the actual covariance structure for the plot errors might be very different. The objective of this study was to identify the most suitable covariance structure and incorporate the error structure in assessment of the crop rotations in terms of yield productivity and yield sustainability. A set of five covariance structures were examined for barley yield data from a 14-year, two-course barley rotation trial conducted at two locations in northern Syria. Selection of the covariance structures was based on the Akaike information criterion (AIC, Akaike 1974) (a function of penalized log-likelihood) obtained from fitting the structure. Covariance structure with heterogeneous variances and with constant correlation between errors over cycles within the same plot was found to account for most variability in grain and straw yields at both locations. Modeling data with this covariance structure, the legume rotations gave higher productivity as well as higher annual increases compared with the continuous barley system. This implies that an agricultural production system based on a legume following a cereal is likely to be more sustainable for cereal production compared to cereal followed by cereals.  相似文献