Showing 4 results for Ahangar
Jahangard Mohammadi,
Volume 2, Issue 4 (winter 1999)
Abstract
This study addresses the methodology of studying spatial variability of soil salinity. The information used is based on a semi-detailed soil survey, followed by a free survey, conducted in Ramhormoz, Khuzestan. The study of soil salinity variations was carried out using about 600 sampling points with an average distance of 500 m, at three depths of 0-50, 50-100, and 100-150 cm. To determine the spatial variability of soil salinity at different depths, the variogram which is a statistical function for the spatial variability analysis of the geographical variables was used. The results indicate that all variograms show almost the same range of 12 - 13 km which is closely related to the geographical distribution of the soil parent materials in the area. Ordinary block kriging was used to map salinity at different depths for a block dimension of 500 × 500 m. A comparison between the kriged estimates and the soil salinity map, produced during the soil survey, showed that the overall similarity between the test data and the classified kriging estimates was 40%, while the overall agreement between the test data and the soil survey salinity map was 36%. A detailed similarity calculation showed that the reliability of the classified kriging estimates representing the lowest salinity classes (S0, S1) is larger (75%) than the reliability of the soil survey salinity map representing these classes (50%). Consequently, the results indicate that geostatistical tools can be used to support the present-day procedures of soil salinity mapping.
Jahangard Mohammadi,
Volume 3, Issue 1 (spring 1999)
Abstract
The analysis of the EC data set indicated that the spatial distribution of EC data of different depths are closely related to one another. It means that they are spatially cross correlated on one another and can be considered to be co-regionalized. It also implies that EC values at a particular depth contain useful information about the other depths which can be used to improve their estimation. In this research, we aimed to investigate the effects of using relevant ancillary information in the estimation procedure. To do this, cokriging was used. To evaluate this algorithm as a potential tool for mapping EC, its performance on the independent test data was evaluated and compared with the results obtained from studies using kriging. The results of the co-regionalization of EC at different depths indicated that cokriging the salinity data, although more rigorous from theoretical point of view, displayed no advantage over independent ordinary kriging at each depth. The results confirmed that cokriging improves little over ordinary kriging if the primary and auxiliary variables are almost equally sampled and all the variograms are identical. Also, ordinary kriging showed to be quite self-consistent since the predicted average salinity profile over the three depths was almost identical to the one predicted by cokriging. Considering the complexity of the cokriging and the LMC modeling, it is clear that there is no gain in using co-regionalization.
R. Hashemi, B. Dastar, S. Hassani, Y. Jafari Ahangari,
Volume 11, Issue 1 (spring 2007)
Abstract
The effect of dietary protein level and feed restriction on performance, body temperature and hematological values was evaluated, using Ross 308 broiler chicks under heat stress. For this purpose, three dietary treatments were fed to broilers during 21 to 42 days of age. Two treatments consisted of diets with protein levels recommended by NRC, 1994 and 85% of NRC recommendation and were fed ad-lib during the experiment. The third treatment was a feed restriction group that was fed diet with protein level recommended by NRC, but chicks were deprived of feed for 6 hours during heat stress challenge. Birds had free access to water. Results indicated that lowering protein content or feed restriction had no significant effect on body weight gain (P>0.05). Feed restriction resulted in significantly decreased feed intake, improved feed conversion and energy efficiency ratio, and decreased body temperature after heat stress challenge at 24 and 32 days (P<0.05). Lowering protein of diet and feed restriction resulted in significantly decreased protein intake, improved protein efficiency ratio and increased hematocrit and blood uric acid (P<0.05). Sex had no significant effect on body temperature and hematological values (P>0.05). Heat stress significantly increased body temperature, hematocrit and glucose and uric acid values.
L Ahangar, Gh Ranjbar, M Norouzi,
Volume 13, Issue 47 (4-2009)
Abstract
Six morphological traits of rice were evaluated in a 5 × 5 one-way diallel cross using a randomized complete block design corresponding with their F1 generations in 2007 at Iranian Rice Research Institute – Amol. Results from analysis of variance for traits of plant height, flag leaf angle, flag leaf length, flag leaf width, internode length and panicle length exhibited significant genetic differences among parental cultivars and their hybrids. Significant means of squares for GCA and SCA showed the positive actions of additive and non-additive effects on controlling these traits. Also, ratio of mean squares of GCA on SCA ( ) were significant in all traits that showing a higher importance for role of additive effects in comparison with role of non-additive effects in functions of genes controlling the studied traits. High narrow sense heritability of these traits proved majority roles for additive effects of genes in genetic control of the studied characteristics therefore, selection of these triats may be succeed. Overall, both of Neda and IR62871-175-1-10 were the best parents for general combining ability for reducting plant height, flag leaf length and internode length and increasing flag leaf width. Meanwhile, because of higher SCA, Neda × Binam and Neda × Dasht were the best hybrids for increasing spike length and decreasing height, respectively.
