تغييرات مكاني رواناب در بخشي از خاك هاي آهكي ناحيه نيمه خشك در شمال غربي ايران

Spatial variations of runoff in a port of calcareous soils of semi-arid region in northwest of Iran

Runoff has an important role in decreasing soil moisture and consequently declining yield of crops. Thus, investigation on spatial variations of runoff and factors affecting runoff is very important in selecting proper method for controlling runoff. The study was conducted base on field measurements of runoff at plot scale in order to determination of spatial variations of runoff and factors affecting runoff in soils of semi-arid regions. Field experiment was carried out in part of dry-farming lands of Hashtroud in south of East Azarbijan, Iran from March 2005 to March 2007. Study area was 30 kmx30 krn and 36 grids with a dimension of 5 krn were considered on it. In each grid, three standard plots with a spacing of 1.2 m were installed and runoff volume measured at the plots under natural rainfall events. Based on results, study soils are clay loam and mostly have about 12.67%. During a 2 study period, 96 rainfall events with a duration time bigger than 30 minute happened and only 41 rainfall events were caused runoff in the plots. Annual runoff in 36 study grids varied from 137.123 to 482.072 liter per plot with an average of 327.157 lit per plot. The results indicated that runoff is significantly (R2~0.63, p