Desert
Year:2003 | Volume:8 | Issue:2|Papers Count:12

Varamin plain has been situated on 45 km of southeastern of Tehran. Jajrood river is a most important river on plain and water capability for agriculture in this plain were provided from this river. Salinization and degradation of this river was cause of desertification in the areas. Therefore, with attention to the importance subject water quality in this river was studied. In this research, after distinguished of main and branches river in the plain, we took some water samples from river and relation between EC with river length was distinguished. Also, with use of water quality and statistical on hydrometry stations like; mamloo on Jajrood river, pol-e-siman on shemiran river, kahrizak on kan river, sharifabad on karaj-jajrood river, relation between EC and SAR months changes with Debbie were determined. Also Water quality of each station in each month from Vilkoks diagram was determined. With use of geological studies on plain, influence of geplogical formation on water quality was studied, and also salt weights that moved from station to the plain was studied. The results showed that from north to south water quality was degrading. That the cause of this subject is entrances of agricultural, industrials and urban sewage, and the other hand to effect of degradation formation.

Recent predication have shown that if current trend in CO2 emission to atmosphere continues, the CO2 concentration will be doubled before the end of this century leading to a drastic changes in climatic patterns all around the world. To predict the probable effects of increased CO2 concentration in Iran, changes in climatic indices were studied using General Circulation Models (GCM"s). The simulation results of GFDL models showed an overall increase in temperature with decreasing gradient from north to south and west to east, but this increase was mainly during spring and summer. Annual precipitation was predicted all over the country to increase by 1 to 35%. However, this increase was during autumn and winter and a decrease in rainfall was predicted for spring and summer. Radiation was hardly affected by increased CO2 level compared to other climatic indices. Mean annual temperature in Tabriz and Mashhad increased by 4.3 and 3.4 degrees centigrade with no considerable changes in annual precipitation. Details on climatic conditions of these two presentative western and eastern cities under doubled CO2 concentration are discussed.

Electromagnetic radiation reflected from ground features is scattered by atmospheric particles and molecules in its way to satellite sensors. This causes some degree of haze in satellite imagery produced. Scattering and its consequent produced haze in imageries vary with time and weather condition. Consequently, image analysis becomes difficult. It is sometimes necessary to omit or at least reduce atmospheric effects on images in hand. This article studies application of an atmospheric correction model on Landsat TM image of an area in north mountainous part of Iran. The result of atmospheric correction was evaluated via comparing the product of maximum likelihood classification on corrected and on non corrected images. The results show that applying this method considerably reduces the haze effect on corrected image and produces higher classification accuracy.

In order to study chickpea rhizobia biodiversity in Khorasan province as one of the major origins of chickpea, root nodules were collected from different parts of the province and a total 36 stain were isolated and purified. 24 isolates were confirmed after infection test, using Leonard jar system and tested with uninoculated and N controls (complete nutrient solution) for nitrogen percent and content, root and shoot dry weight, symbiotic effectiveness and the number and weight of nodules in aseptic N-free hydroponic sand culture system. Results indicated significant differences (p< 0.01) among isolates for all parameters studied. Root nitrogen content was lower than shoot in all isolates indicating transfer of nitrogen from root to shoot immediately after biological fixation. Regression coefficient for nodule numbers with shoot nitrogen content was low. Finally five superior isolates were selected in terms of shoot nitrogen content and symbiotic effectiveness. In the last trial, symbiotic effectiveness in four chickpea cultivars (two Kaboli and two Desi type) were evaluated by inoculating with selected isolates under soil conditions. In general, all isolates increased nodules in inoculated plants, although these differences were statistically significant only for few isolates. Nodule numbers in Kabuli cultivars were significantly higher than Desi cultivars. Dry weight of inoculated plants were higher from 2.5 percent in introduced isolate CP36 to 19.3 percent in isolate no. 27 as companed, Compared with control (80 kg N/ha). Simbiotic effectiveness in Flip chickpea cultivar was 31.8 percent higher than N control and this was the highest between- chickpea cultivars. This study indicated that inoculation of chickpea cultivars with local isolates, increased shoot and plant dry weight, nodulation and symbiotic effectiveness.

One of the most important problem facing human corelization is desertification phenomenon. Saline areas are developing in desert lands. Plants in saline areas have adapted themselves to salinity stress. To avoid desertification and saline areas, it is necessary to investigate the ecosystem elements and their relationships in saline areas. In the latter, soil factors affect plant growth and development. In this study, plant species and density and soil salinity and texture were investigated at a constant slope. There was a significant relationship between plant density and distribution. Different species showed different degrees of tolerasnce to soil salinity and they ranged from very tolerant to non-tolerant species. Very tolerant species were found at the center of saline areas and non-tolerant at the edges. Among tolerant species, Holacnemum strobilaceum showed a maximum tolerance and they can be used for control of saline areas were as Gymnocarpus decander was found to be suitable for the edges of salines areas inorder to avoid salinity development.

Intercropping of pearl millet and common vetch was studied at Research Station of Faculty of Agriculture, University of Tabriz in 1999. The experimental design was randomized complete block with 3 replications. The treatments consisted of constant density of pearl millet with 15 kg/ha and three density of common vetch with 50, 70, 90 kg/ha and their combinations with the total of seven treatments. Intercropping system was additine. On the basis of standard LER, intercropping of pearl millet var. Nutrifeed with the third level of common vetch (90 kg/ha) was better than other the combinations. Its LER was 1.56. In some intercropping treatments, pearl millet yield in the second harvest was more than the first one. It seems that pearl millet exploited nitrogen remained prom vetch and decreased its interplant competition. Pure stand of common vetch was worthy of recommendation because of shorter growth period, optimum yield, better forage quality and improved soil fertility.

Food security is equal to yield stability. Fifty percent observed yield variability of irrigated wheat in Khorasan province indicates that these are no reliable food security. Crop growth simulation model as a quantitative tool based on scientific principles that could evaluate different climatic effects, soil, water and management factors on crop production. CERES-Wheat model is a widespread model, which has been employed in many studies across the world.To evaluate CERES-Wheat model in yield predication, two completely randomized Block Design experiments with four replications were conducted in two different climatic locations, using six cultivars released between 2001-2002 years. The experiments were carried out at Mashhad and Birjand agricultural research stations. Genotype coefficient and cultivars differences were determined using GENCALC software. To evaluated the yield, Root Mean Square Error (RMSE) was calculated and formed to be 44.44 and 62.7 Kg/ha for Mashhad and Birjand trails respectively this was less than 10% of observation mean as a model accuracy. Because of agricultural complexity, it was difficult to have access to input data, and unknown physiological properties, specially interaction under different condition and environments cause discrepancy in model simulations thus indicating that model validation and calibration is necessary before applying the model in any future application as a research tool.

In order to quantitatively assess desertification in Bijar an in present regional model, a study was carried out in an area of 2037 hectares. Following the examination of existing models and studying 17 units based on geomorphological facies a model was suggested and evaluated. In this model three aspects studied. The study units were then mapped into various classes. It was possible to determine the current and potential conditions of desertification as well as management of arid ecosystem.

Drought, as an integrated part of climate variability, may be investigated through many different aspects. In this study, severity, duration and frequency (SDF) of meteorological drought in Sistan and Belochestan province were investigated. In order to construct Z-score time series, homogeneous data set was established and standardized for each individual month. Using run theory and based on a selected truncation level, dry, wet and normal months and periods were determined and eventually the SDF curves were derived. In the next step, transition probability matrix and equilibrium transition matrix were developed for each station via combination of run theory and Markov Chain. Finally, the long-term condition of the region from drought point of view was investigated and probability of drought occurrence and length of drought events for the next 10 years were predicted.

In order to evaluating the effects of different amounts of salinity and CI-/So42- ratios on Nitrogen (N) uptake in wheat, a greenhouse study was conducted through a factorial experiment based on the completely randomized design with three replications. The experimental treatments were three levels of salinity [S1 (2dS/m), and S2 (4dS/m) S3 (8dS/m)], three CI-/So42- ratios [R1 (CI-/So42- =1/2), R2CI-/So42- =1/1) and R3 (CI-/So42- =2/1)] in irrigation water and also two levels of Nitrogen [N1 (100KgN/ha) and N2 (200KgN/ha)]. Results of salinity showed significant reduction (at 5%) in seed germination in S3 in relation to S1 and S2 that were about 15% and 11 % respectively. The decreasing in plant height due to increasing of salinity was not significant. Plant dry matter weight decreased at 83 significantly about 24.5% and 12% in relation to S1 and S2, respectively (at 5%). The comparison of CI-/So42- ratios for seed germination, plant height, and dry matter weight didn't show any significant differences. Increasing the amount of N fertilizer from N1 to N2 resulted in a significant increment in plant dry matter weight. The comparison of interaction effects between CI-/So42- ratios and N fertilizers showed that in soils having R1 and R2 ratios, the increment of N fertilizer could increase the plant dry matter. The result of this study suggest that the use of N fertilizer in saline soils may prevent the stresses of salinity through improvement in growth and yield of wheat only when So42- is a dominant anion or their CI-/So42- ratios are 1:1 and 1:2.