Evalution the efficiency of mechanical and biological management practices on wind erosion in inTal Hamid rail way Station of Tabas

Wind erosion is a serious problem in many parts of the world, especially in arid and semi-arid regions and it is an important factor in soil degradation and loss. In most area, conservation operations against the wind erosion are appropriate practices.There are two main strategies to combat wind erosion. These first strategy is to increase the strength of erodible bed against erosive factorsand second one is to reduce the force of erosive factors. Seedling is the more effective solution to reduce speed of wind, to combat wind erosion and to stabilize the drifting sands. Therefore, the objective of this research was to study the effect of mechanical and biological management practices on the amount of wind sediment in Tal-Hamid area, which is located in Tabas (Khorasan Razavi province, Iran).

In order to determine the role of each management practices on wind erosion and its control, sediment traps were established at different distance between conservational practices at 0.5, 1 and 1.5 meters from the surface of the earth. Conservational treatments included T1 (4 rows seedlings of Haloxylon persicum and 3 rows native plant of Stipagrostis) T2 (fence and sand channel), T3 (one row of Hammada Salicornica, 3 rows seedlings of Haloxylon persicum, and one row Stipagrostis), and T4 (moat and Railroad tie). Also, a control sediment trap was regarded in adjacent area without any conservational practices. The management practices had been performed for 3 years. After then sediment traps were established in December 2015, and according to wheatear information, after each wind storm (two times in each month) the trapped sediments were collected and weighted in established sediment traps for each treatments from January to June 2016 (spring and winter seasons).

The results showed that all conservational practices were effective to reduce amount of sediment and the effect of T1 and T2 in reduction the wind sediment was considerably greater than other treatments. The more reduction of sediment load was found at height less than 0.5 m, therefore it can be concluded that the biological and mechanical practices could considerably prevent the saltation movement of sand particles. The wind sediment during the spring (due to lower moisture content and greater wind speed) was more than the winter. In addition, among the conservational treatments, the lowest value of wind sediments was related to mechanical management practices (fence and channel) and the highest amount of wind sediments was related to biological management practices (four rows of Haloxylon, and native plant i.e. Stipagrostis) in both seasons, because T4 and T3 are the first hedges against wind direction and they are located behind T2, and considerably have decreased the speed of wind, therefore when low speed wind reach to T2 its speed and energy is low. As a result of this, the sediment load In T2 was the lowest.

In general, biological and mechanical management practices decreased considerably the amount of wind sediment compared to the control. In spite of common viewpoint, the biological management practices may decrease the wind erosion, but due to unsuitable growth of Haloxylon seedlings and plants as a result of drought duration and deficiency of water, their efficiency in reduction of wind speed and energy especially T1 and T3 was not more than mechanical management practices (T2). It seems that during 3 years Haloxylon seedlings have not been grown sufficiently, and if they grow for long time, they can decrease the wind erosion considerably. According to results of this research, application both simultaneous biological and mechanical practices are needed to control wind erosion in arid regions such as Tabas.