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61.
Ferede Brikti Mekbib Firew Assefa Kebebew Chanyalew Solomon Abraha Eyasu Tadele Zerihun 《Journal of Crop Science and Biotechnology》2020,23(2):107-115
Journal of Crop Science and Biotechnology - A field experiment was conducted to identify drought tolerant, high yielding and stable tef genotypes using drought tolerance indices. Sixty-four tef... 相似文献
62.
Within the western United States, water rights are granted for reasonable and beneficial water use, and a measure of irrigation performance that embodies this standard is needed. A new performance parameter, irrigation
sagacity (IS), is recommended for this purpose. The term `sagacity' comes from `sagacious', meaning wise or prudent. IS is
more closely tied to the water rights granted, and to the potential for water conservation and reallocation than is the traditional
irrigation efficiency, which considers only beneficial uses. Sagacious uses are either beneficial, or non-beneficial but reasonable.
Reasonable uses are those that, while not directly benefiting agronomic production within the boundaries of the water rights
area, are nonetheless justified under prevailing conditions. Non-sagacious uses (non-beneficial and unreasonable) are those
uses which are without economic, practical, or other justification. Determination of sagacity involves checking alternate
irrigation practices for practical, technical, economic, and environmental feasibility. Feasibility includes the requirement
for a reasonable implementation schedule for any new practices. Only if a feasible alternate using less water is found should
a current practice be considered in any part non-sagacious. The results of a sagacity determination may vary depending on
geographic scale, time frame, and perspective.
Received: 27 September 1997 相似文献
63.
Carbon pools and flux of global forest ecosystems 总被引:40,自引:0,他引:40
Dixon RK Solomon AM Brown S Houghton RA Trexier MC Wisniewski J 《Science (New York, N.Y.)》1994,263(5144):185-190
Forest systems cover more than 4.1 x 10(9) hectares of the Earth's land area. Globally, forest vegetation and soils contain about 1146 petagrams of carbon, with approximately 37 percent of this carbon in low-latitude forests, 14 percent in mid-latitudes, and 49 percent at high latitudes. Over two-thirds of the carbon in forest ecosystems is contained in soils and associated peat deposits. In 1990, deforestation in the low latitudes emitted 1.6 +/- 0.4 petagrams of carbon per year, whereas forest area expansion and growth in mid- and high-latitude forest sequestered 0.7 +/- 0.2 petagrams of carbon per year, for a net flux to the atmosphere of 0.9 +/- 0.4 petagrams of carbon per year. Slowing deforestation, combined with an increase in forestation and other management measures to improve forest ecosystem productivity, could conserve or sequester significant quantities of carbon. Future forest carbon cycling trends attributable to losses and regrowth associated with global climate and land-use change are uncertain. Model projections and some results suggest that forests could be carbon sinks or sources in the future. 相似文献
64.
Moisture-dependent physical properties of niger (Guizotia abyssinica Cass.) seed were studied at 5.60, 12.99, 19.77, 27.08 and 31.65% moisture content (wet basis). The length, width, thickness and geometric mean diameter increased significantly (p < 0.05) from 3.86 to 4.06 mm, 0.96 to 1.02 mm, 0.86 to 0.96 mm and 1.47 to 1.59 mm, respectively with increase in moisture content from 5.60 to 31.65% whereas the increase in sphericity from 38.10 to 39.01% was not significant. Similarly, thousand seed mass, porosity and angle of repose increased (p < 0.05) linearly from 2.50 to 3.69 g, 41.76 to 47.65% and 29.86° to 39.12°, respectively with increase in moisture content under the experimental condition. The bulk density decreased significantly (p < 0.05) from 635.23 to 561.06 kg m?3 with increase in the moisture content range considered in the study, whereas the true density showed a slight increase from 1090.71 to 1098.42 kg m?3 with increase in moisture content from 5.60 to 27.08% followed by a drop from 1098.42 to 1071.75 kg m?3 as moisture content increased from 27.08 to 31.65%. Coefficient of static friction increased (p < 0.05) logarithmically from 0.34 to 0.51, 0.38 to 0.56 and 0.13 to 0.53 on mild steel, plywood and glass surfaces, respectively with increase in moisture content from 5.60 to 31.65%. 相似文献
65.
S E Solomon 《British poultry science》1975,16(3):255-258
The isthmus extends from the aglandular zone, which delimits it from the magnum, to the tubular shell gland, which to the naked eye is marked by a distinct colour change from off-white to brown. 2. The surface epithelium comprises three cell types, ciliated, non-ciliated and mitochondrial, of which only the non-ciliated cells contribute towards the carbohydrate moiety of the shell membranes. 3. The gland cells are distinctive, containing granules of variable electron density, variations also occurring within individual granules. 4. Although two types of gland cell have been observed, they may merely represent different phases of development. 5. In the type 1 cell, the rough endoplasmic reticulum and Golgi complex are typical of the normal protein secreting cell; in the type 2 cell the RER is sparse, dilated and filled with intracisternal granules while the Golgi complex is likewise distended. 相似文献
66.
Eric A. S. la Croix Solomon E. Mhasalkar Patrick Mamalis Frank P. Harrington 《Pest management science》1975,6(5):491-496
A series of analogues of the larvicide tenuazonic acid [3-acetyl-5-(l-methylpropyl)-pyrrolidine-2,4-dione] was prepared in an attempt to increase its activity and breadth of spectrum. Substitution brought about some changes in specificity, the greatest improvement being obtained with chlorophenyl substituents. 相似文献
67.
68.
Vann RC Althen TG Solomon MB Eastridge JS Paroczay EW Veenhuizen JJ 《Journal of animal science》2001,79(1):108-114
The objective of this study was to determine the effect of recombinant bovine somatotropin (rbST) on muscle fiber histology and histochemistry in creep-fed beef steers. Crossbred steer calves were assigned to one of two treatment groups: control (sham-injected; n = 12) or rbST-injected (0.09 mg x kg(-1) x d(-1); n = 12). Calves were injected every 14 d starting at d 28 of age until weaning at 205 d of age. Biopsies of the semitendinosus muscle were performed on d 100, and slaughter samples of semitendinosus muscle were collected for muscle fiber analyses on d 206. The rbST-treated calves had larger (P = 0.045) fast-twitch-glycolytic (FG) fibers [2,564 +/- 10 vs 2,351 +/- 11 microm2 cross-sectional area, respectively] than controls. No differences (P = 0.36) between rbST-treated and control steers in cross-sectional area were detected for slow-twitch-oxidative (SO) [1,192 +/- 20 vs 1,148 +/- 22 microm2, respectively] or fast-twitch-oxidative-glycolytic (FOG) fibers [1,484 +/- 35 vs 1,403 +/- 38 microm2, respectively]. The percentage distribution for FOG fibers was greater for control calves than for the rbST-treated calves (38.4 vs 34.9 +/- 0.1%, respectively; P = 0.014), whereas the percentage distribution for FG fibers was greater in the rbST-treated calves than for control calves (53.5 vs 48.4 +/- 0.2%, respectively; P = 0.03). The percentage distribution for SO fibers tended to be greater for the control calves than for the rbST-treated calves (13.1 vs 11.7 +/- 0.1%, respectively; P = 0.07). The percentage of FG fibers increased with age (45.4 vs 56.6 +/- 0.8%, respectively; P = 0.001), whereas the percentage distribution of SO (14.3 vs 10.5 +/- 0.5%, respectively) and FOG fibers (40.3 vs 32.9 +/- 0.7%, respectively) decreased (P = 0.001) from d 100 to d 206. The increased longissimus muscle area and dissectable lean tissue in rbST-treated calves are associated with a greater percentage of FG fibers, which possess larger cross-sectional areas than the other fibers. 相似文献
69.
Soil organic matter quantity and quality in mountain soils of the Alay Range, Kyrgyzia, affected by land use change 总被引:4,自引:0,他引:4
Changes in soil management practices influence the amount, quality and turnover of soil organic matter (SOM). Our objective
was to study the effects of deforestation followed by pasture establishment on SOM quantity, quality and turnover in mountain
soils of the Sui Checti valley in the Alay Range, Kyrgyzia. This objective was approached by analysis of total organic C (TOC),
N, lignin-derived phenols, and neutral sugars in soil samples and primary particle-size soil fractions. Pasture installation
led to a loss of about 30% TOC compared with the native Juniperus turkestanica forests. The pasture soils accumulated about 20% N, due to inputs via animal excrement. A change in land use from forest
to pasture mainly affected the SOM bound to the silt fraction; there was more microbial decomposition in the pasture than
in the forest silt fraction, as indicated by lower yields of lignin and carbohydrates, and also by a more advanced oxidative
lignin side-chain oxidation and higher values of plant : microbial sugar ratios. The ratio of arabinose : xylose was indicative
of the removal of carbohydrates when the original forest was replaced by pasture, and we conclude that this can be used as
an indicator of deforestation. The accumulation of lignin and its low humification within the forest floor could be due to
the extremely cold winter and dry summer climate.
Received: 10 March 1999 相似文献
70.
Effects of deforestation on phosphorus pools in mountain soils of the Alay Range, Khyrgyzia 总被引:4,自引:0,他引:4
The amount, quality and turnover of soil P is heavily influenced by changes in soil management. The objective of this study
was to investigate the effects of deforestation and pasture establishment on the concentrations, forms and turnover rate of
soil P in mountain soils of the Alay Range, Khyrgyzia. A sequential extraction was applied to distinguish soil P pools. We
used particle-size fractionation to follow the dynamics of different P pools in soils under forest and pasture and 31P-NMR spectroscopy to investigate the structure of alkali-soluble P forms. In the A horizons of the forest soils, total soil
P concentration was 1093 mg kg–1, organic P (Po) representing 46% of the total P. Deforestation followed by pasture establishment not only increased significantly (P<0.01) the total P concentration (1560 mg kg–1) but also the contribution of Po to total P was increased by 17%. Pasture soils had significantly higher P pools than forest soils except highly labile inorganic
P (Pi NaHCO3) and primary Pi (Pi HCldil). Both in forest and pasture soils stable P increased with decreasing particle size (coarse sand 50%, clay 80% of total P)
and primary P decreased with decreasing particle size. Phosphate monoesters and diesters represented 80% of P identified by
31P NMR. Low monoester to diester ratios in the alkali extracts of forest and pasture soils indicate low microbial activity.
This is consistent with high C/Po ratios and high stable Po concentrations in the fine earth of forest and pasture.
Received: 10 March 1999 相似文献