@article{ author = {}, title = {Various Levels of Calcium and Phosphorus Diets in Response to 1, 25 – Dihydroxycholecalciferol in Laying Hens}, abstract ={The effect of 1,25-dihydroxycholecalciferol [1,25-(OH)2 D3 ] supplementation on laying hen diets was evaluated using diets high and low in Ca (3.0% and 1.8% ) and high and low in P( 0.52% and 0.33% ). Since two levels of 1,25- (OH)2 D3 supplementation (0 and 5 µg/kg diet ) were applied, the experiment was a 2 X 2 X 2 factorial arrangement in a com-pletely randomized design using nine individually housed hens per each 8 treatments (72 in total). The hens were fed the diets for 28 days and records were kept on body weight, egg production, feed intake, egg weight, and egg specific gravity. At the end of the ex-periment, the hens were bled for plasma Ca and P determination and after being eutha-nased the left tibia removed for bone ash measurement. The corn-soybean meal based diet contained 0.1% Cr2O3 as an indicator for determining Ca, P and phytate phosphorus re-tention at 14 and 28 days. 1, 25-Dihydroxycholecalciferol supplementation had no effect on hen weight, egg production or feed intake. However, large increases in egg specific gravity were obtained when 1, 25-(OH)2 D3 was fed to hens receiving the low Ca diet. All of the treatments had significant effects on bone ash. The greatest effect of 1, 25-(OH)2 D3 on bone ash was obtained in those hens fed the high Ca and P diet that was then supple-mented with 1,25-(OH)2 D3 (49.3% vs 53.9% bone ash). At day 14, the high Ca diets de-creased phytate P retention while at d 28 the high P diets decreased phytate P retention.}, Keywords = {Phosphorus,Calcium,1,25-dihydroxycholecalciferol,Phytate phosphorus}, volume = {7}, Number = {3}, pages = {0-0}, publisher = {Tarbiat Modares University}, title_fa = {}, abstract_fa ={}, keywords_fa = {}, url = {http://jast.modares.ac.ir/article-23-10225-en.html}, eprint = {http://jast.modares.ac.ir/article-23-10225-en.pdf}, journal = {Journal of Agricultural Science and Technology}, issn = {1680-7073}, eissn = {2345-3737}, year = {2005} } @article{ author = {}, title = {Evaluation of Three Physiological Traits for Selecting Drought Resistant Wheat Genotypes}, abstract ={Physiological traits are receiving increasing attention as screening tools for drought re-sistance. Two field experiments were conducted in 1998 at the Experimental Station of College of Agriculture, Shiraz University at Badjgah, to evaluate the effectiveness of leaf water potential, leaf osmotic potential and canopy temperature in screening resistant bread wheat (Triticum aestivum L.) genotypes. Nine wheat cultivars consisting of drought resistant, intermediate and susceptible genotypes were grown in two randomized com-plete block designs with three replications. The experiments only differed with respect to their irrigation regimes. Leaf water potentials and leaf osmotic potentials at three devel-opmental stages -stem elongation, booting and flowering - under water stress conditions, and canopy temperature in non-stress conditions could discriminate between resistant and susceptible cultivars. Although the drought susceptibility index could partly dis-criminate between resistant and susceptible cultivars, it was not evaluated as a reliable index. The linear regression of grain yield on each trait was determined. The linear re-gressions of grain yield on leaf water potential; leaf osmotic potential and canopy tem-perature confirmed the above results.}, Keywords = {Canopy temperature,Triticum aestivum,Leaf water potential,Osmotic potential,Turgor potential}, volume = {7}, Number = {3}, pages = {81-87}, publisher = {Tarbiat Modares University}, title_fa = {}, abstract_fa ={}, keywords_fa = {}, url = {http://jast.modares.ac.ir/article-23-2075-en.html}, eprint = {http://jast.modares.ac.ir/article-23-2075-en.pdf}, journal = {Journal of Agricultural Science and Technology}, issn = {1680-7073}, eissn = {2345-3737}, year = {2005} } @article{ author = {}, title = {Developing Diameter at Breast Height (DBH) and a Height Estimation Model from Remotely Sensed Data}, abstract ={While most recent investigation in satellite- based remotely sensed data has concen-trated upon the biophysical characteristics of overstory vegetation for large area, little at-tention has been given to the reflectance contribution of their associated understory, ver-sus overstory plantation reflectance to the recorded pixel value. In this research, shrubs and herbs were considered as consistent backgrounds which have an inverse effect, in contrast to plantation overstory, to the recorded pixel value in terms of their surface-exposure to satellite sensors. Given the fact that planted tree crown closure is correlated with their height and diameter at breast height (DBH) in the early stages of the planta-tion, it is expected that a relationship exists between tree canopy closure, height, DBH and their associated reflectance values. The proposed concept was tested in a case study for a Jack Pine (pinus banksina) plantation using Landsat Thematic Mapper (T. M.). The crown width height, and DBH of planted trees were measured in an area of 30m X 30m, for every 2-year age interval from 1 to 21 years. Other understory natural regeneration within a 2m radius was recorded. Crown closure, mean height, and DBH of each plot (with shrub and herb understory of more than 60%) were plotted against their associated Digital Numbers (DN(s)) for 6 T. M. bands (1, 2, 3, 4, 5 and 7). The visible region of the spectrum (bands 1, 2 and 3) showed a narrow range of reflectance and was not suitable for this purpose. Band 4 revealed a greater range of DN(s) than bands 1, 2 and 3. A strong inverse linear relationship between DN(s) and their associated canopy closure, height, and DBH were found in band 5 as r2 = 0.863, 0.941, 0.873 respectively. Band 7 showed a stronger relationship with canopy closure (r2 = 0. 81) than did the other T. M. bands (ex-cept band 5). Overall, the results of this study have shown the importance of T. M. band 5 for estimating DBH and the height of plantations based on the contrast between reflec-tance of the overstory and understory.}, Keywords = {Canopy closure,DBH,DN(s),Height,Satellite data,T. M. bands}, volume = {7}, Number = {3}, pages = {95-102}, publisher = {Tarbiat Modares University}, title_fa = {}, abstract_fa ={}, keywords_fa = {}, url = {http://jast.modares.ac.ir/article-23-8674-en.html}, eprint = {http://jast.modares.ac.ir/article-23-8674-en.pdf}, journal = {Journal of Agricultural Science and Technology}, issn = {1680-7073}, eissn = {2345-3737}, year = {2005} } @article{ author = {}, title = {Verticillium-toxins: Their Role in Pathogenesis}, abstract ={Bioassay results confirmed the role of low molecular weight phytotoxin in the patho-genesis of Verticillium albo-atrum. The metabolites separated from 21-day-old culture fil-trate by adsorption on the resin Amberlite XAD-4, and further chromatographed on Bio-Gel P2 polyacrylamide gel, induced chlorosis and necrosis on the leaflets of tomato and potato cultivars, similar to those caused by the fungus on diseased plants. Leaflets from tolerant cultivars were much less sensitive to the toxin (s) than those from the susceptible ones. In the presence of toxin(s) plant tissues and individual cells showed ion-leakage and cell death to an extent relating to the plants reaction to the fungus. The relative specificity observed during pathogenicity tests between potato and tomato and their related isolates was shown to be related to the action of toxin (s).}, Keywords = {Pathogenesis,Toxins,Verticillium}, volume = {7}, Number = {3}, pages = {103-114}, publisher = {Tarbiat Modares University}, title_fa = {}, abstract_fa ={}, keywords_fa = {}, url = {http://jast.modares.ac.ir/article-23-1066-en.html}, eprint = {http://jast.modares.ac.ir/article-23-1066-en.pdf}, journal = {Journal of Agricultural Science and Technology}, issn = {1680-7073}, eissn = {2345-3737}, year = {2005} } @article{ author = {}, title = {A New Method for Determining the Soil Erodibility Factor Based on Fuzzy Systems}, abstract ={Determination of the soil erodibility factor (K-factor) is a cumbersome and expensive undertaking in the effort to predict the soil loss rates. The percentage of soil particles less than 0.1 mm in diameter, the percentage of organic matter, the structural as well as the textural class and permeability are the most important factors constituting the soil erodi-bility factor. Various methods of direct measurement for indirect prediction using models have been introduced so far for the measurement of K- factor. Using the new topics in in-formation technology, in particular the fuzzy system including the Mamdani Inference Engine, Singleton Fuzzyfier and Centriod Defuzzyfier can determine the soil erodibility factor. The K values obtained with this method were compared with those of USLE method. Over 394 samples based on the Wischmeier nemograph as a database were in-cluded in this research work by using the fuzzy system. Using some actual data in the fuzzy system and comparing it with the K values attained with the USLE model by calcu-lation of the regression coefficient, the applicability of this system was revealed.}, Keywords = {Fuzzy Systems,RUSLE model,Soil erodibility,USLE model}, volume = {7}, Number = {3}, pages = {115-123}, publisher = {Tarbiat Modares University}, title_fa = {}, abstract_fa ={}, keywords_fa = {}, url = {http://jast.modares.ac.ir/article-23-2779-en.html}, eprint = {http://jast.modares.ac.ir/article-23-2779-en.pdf}, journal = {Journal of Agricultural Science and Technology}, issn = {1680-7073}, eissn = {2345-3737}, year = {2005} } @article{ author = {}, title = {Soil Organic Carbon Dynamics Under Tropical Garden Land Systems}, abstract ={The organic carbon (OC) status of three continuously cropped permanent manurial ex-periments, under different cropping systems, over a period of time is discussed in this pa-per. The Old Permanent Manurial Experiment (OPME) was originally an irrigated ex-periment started in 1909 and in 1937, converted into a rainfed experiment (at this time the cropping system was converted from two crops per year into a single crop per year). The New Permanent Manurial Experiment (NPME) was started in 1925 and was con-ducted in an irrigated system with one set of treatments receiving 2 t ha-1 of cattle manure since its inception. These two experiments were conducted with different nutrient input management systems of single inorganic nutrients and their combinations. The effect of these treatments on the OC status of the soil was evaluated. Along with these, the changes in the OC status of another irrigated long term fertilization trial which has been con-ducted since 1972 under the intensive cultivation system with three crops per year were studied. The results obtained in the three experiments showed that there was a build up in the OC status of the soil for the balanced application of N, P, and K combined with an or-ganic manure. Among the inorganic fertilizer treatments, the combined application of all the three major nutrients (N, P and K) resulted in a higher OC status, compared to the application of single nutrients. This may be due to better growth and a higher amount of root residues added after the harvest of each crop, over a period of time. But, in both OPME and NPME, there was a decline in the OC content after seven years and a build up has happened in the last nine years. Under the intensive cropping system of cultivation, the soil organic carbon build up occurred in all the treatments, including the unmanured control, and was the maximum for the combined application of inorganics and organics (100% NPK + Farm Yard Manure (FYM)). The increase in OC is attributed to enhanced root biomass over a period of 30 years.}, Keywords = {Organic manure,Permanent Manurial Experiments,Soil organic carbon}, volume = {7}, Number = {3}, pages = {125-131}, publisher = {Tarbiat Modares University}, title_fa = {}, abstract_fa ={}, keywords_fa = {}, url = {http://jast.modares.ac.ir/article-23-10595-en.html}, eprint = {http://jast.modares.ac.ir/article-23-10595-en.pdf}, journal = {Journal of Agricultural Science and Technology}, issn = {1680-7073}, eissn = {2345-3737}, year = {2005} } @article{ author = {}, title = {A Semi-Detailed Technique for Soil Erosion Mapping Based on BLM and Satellite Image Applications}, abstract ={An ever increasing population needs more energy and food to be provided from limited resources. Many different problems such as floods and droughts frequently occur and even happen at extreme values throughout the world, since the inherent capability of the resources is not evaluated properly. Soil erosion, as one of the major types of land degra-dation, is supposed to cause serious problems for future and even present generations. However, evaluation of the magnitude and spatial distribution of fundamental types of soil erosion i.e. sheet, rill and gully erosion is an important task to be conducted in devel-oping countries where the necessary bases for development are required. An attempt has been made in the present paper to introduce a technique through which the condition of soil erosion is defined and mapped in the study area. All available and acceptably accu-rate information, such as the geologic sensitivity of the area to erosion, the land type and slope maps, are required for determination of homogeneous work units using overlying. The present character of soil erosion in the field is then evaluated by filling out the revised questionnaire forms adjusted on the basis of criteria mentioned by United States Bureau of Land Management (USBLM) and the final classification of each type of erosion is made according to the sum of scores obtained by each work unit. Finally, the overall situation is generalized in the fractional form. The presented technique has been implemented for more than 6 million hectares of the area of Iran and was able to reflect the governing conditions well and the results should be applied in the management of natural resources to achieve sustainable utilization. For the present study and for demonstrating the details of methodology, a small watershed located in the Markazi large watershed of Iran, known as Barahmoom, and comprising 4236.2 ha was selected as a case study. The presented soil erosion mapping technique can be applied for areas where only basic or very little data and information is available.}, Keywords = {Remote Sensing,BLM,Markazi Province,Soil Erosion Mapping,Water erosion}, volume = {7}, Number = {3}, pages = {133-142}, publisher = {Tarbiat Modares University}, title_fa = {}, abstract_fa ={}, keywords_fa = {}, url = {http://jast.modares.ac.ir/article-23-5904-en.html}, eprint = {http://jast.modares.ac.ir/article-23-5904-en.pdf}, journal = {Journal of Agricultural Science and Technology}, issn = {1680-7073}, eissn = {2345-3737}, year = {2005} } @article{ author = {}, title = {Relationships Between Characteristics of Plant Communities and Climatic Conditions at Qara Soo Catchment Area, Gorgan}, abstract ={In order to understand the relationships between climatic factors and the biological variables of plant communities in the Qara Soo Catchment Area, a systematic sampling of natural plant community variables such as crown closure, diversity, reproduction rate and crown height has been taken. Information about physical components of the ecosys-tems such as climatic elements, soil properties and topographic characteristics was also collected for each plant community. By using the Numerical Taxonomy Model suggested by Sneath and Sokal (1963), the plant communities were classified and sorted according to a “development index” which indicates the plant community development toward the climax stage of ecosystem. Then the relationships between ecosystem physical components and the biological variables of communities (development index) were understood by us-ing a multiple regression model. It was concluded that climatic elements are the dominant factor affecting on the formation, distribution, reproduction and stability of plant com-munities in the area. It was further concluded that the Numerical Taxonomy Model, which has been commonly used by social scientists, is a suitable tool for system analysis in plant communities and natural ecosystems.}, Keywords = {Climate,Ecosystem components,Plant community,Qara Soo}, volume = {7}, Number = {3}, pages = {143-150}, publisher = {Tarbiat Modares University}, title_fa = {}, abstract_fa ={}, keywords_fa = {}, url = {http://jast.modares.ac.ir/article-23-3986-en.html}, eprint = {http://jast.modares.ac.ir/article-23-3986-en.pdf}, journal = {Journal of Agricultural Science and Technology}, issn = {1680-7073}, eissn = {2345-3737}, year = {2005} }