JWSS - Journal of Water and Soil Science

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Spatial and temporal distribution of dust deposition rate (DDR) in Isfahan city and the influencing climatic parameters were studied. Dust samples were collected using glass trays placed on the roof of one-story buildings from 20 sites in Isfahan city for 12 months. Climatic data were obtained from Meteorological Organization and analyzed. The highest and the lowest amount of DDR in agreement with the direction of prevailing wind were observed for dry months with eastern and northeastern wind directions and wet periods with western and southwestern wind directions, respectively. This can indicate dust emission from the desert located in eastern part of Isfahan city. Statistically significant inverse correlation between DDR and precipitation and relative humidity, and significant and positive correlation of DDR with Min and Max temperatures in all the studied months and also with Max and average wind speed for dry sampling months may well justify the temporal distribution of DDR in the city. In dry months, finer particles from eastern desert can be transported a longer distance and deposited in the western part of the city, far from the source area. In wet seasons, however, soil aggregates become coarser as a result of particle adhesion. This, in turn, results in the deposition of dust near the source area as the transporting power of dust reduces.

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Earthworms are an important component of soil fauna because of their fundamental impact on soil physical, chemical and biological properties. To evaluate the effects of earthworms on some soil chemical properties as well as plant growth indicators, an experiment was carried out in a completely randomized design in greenhouse conditions. The first factor involved the presence or absence of earthworms (Eisenia foetida), the second factor was different organic matter including control (no organic materials), pruning waste compost of apple and grape (PWC), wheat straw (WS), Herbal extracts waste (HE), pruning waste (PW) and the third factor was the presence or absence of corn plant for evaluating rhizosphere soil. At the end of growing period, some soil chemical properties including total nitrogen, organic carbon, ammonium, nitrate and plant growth indicators were measured. The results showed that application of organic matter and earthworm inoculation had significant effects on soil chemical properties. The pruning waste compost (PWC) treatment showed the largest impact on ammonium and nitrate content (1.7 and 3.3 times compared to control treatment, respectively). In pruning waste compost (PWC) treatment, organic carbon amount in rhizospheric soil increased from 0.9 at non-rhizosphere to 1.32 %. The presence of earthworm improved plant growth parameters including shoot and root dry weight by 34% and 30%, respectively, compared to earthworm absence condition. Soil ammonium and nitrate contents at earthworm presence increased 32% and 49%, respectively. Therefore, application of organic matter with earthworm inoculation had better results in comparison with no earthworm inoculation.

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Prioritization of sub-watersheds is very important and necessary in order to implement soil and water conservation practices. This study has prioritized 13 sub-watersheds based on morphometric and land use characteristics using RS and GIS techniques in Haraz watershed to identify erosion-prone sub-watersheds. Morphometric characteristics including bifurcation ratio, drainage density, stream frequency, drainage texture, form factor, basin circularity, compactness coefficient, elongation ratio, length of overland flow, shape index, and basin relief were considered in morphometric analysis. Land use map was classified into seven classes of forest, water-body, irrigated farming, bare land, rangeland, orchard and residential area. Finally, sub-watersheds were classified into four categories as very high, high, medium and low in terms of priority for soil conservation. On the basis of morphometric analysis sub-watershed WS-4 was considered as high priority, whereas according to land use analysis, sub-watersheds WS-6, WS-8, WS-12 were in class of high priority. Sub-watershed WS-4 was categorized as a very high priority class based on the integration of morphometric and land use analysis. This region was identified as critical region therefore should be considered as priority class for implementation of soil and water conservation practices.

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