Comparison of the Effects of Straw on Physical Quality of Two Fine and Coarse-Textured Soils from Moghan Plain, NorthWest of Iran

In this study, the effects of wheat straw on physical quality indices of two sandy loam and clay loam soils were compared. Factorial experiment was conducted as a randomized block design at 4 replicates. The first factor was straw used rates at 5 levels including 0, 1, 2, 3 and 5 mass percent; the second factor was 2 soil textural classes. Soil columns were incubated at the temperature of 22±4 °C and moisture of 50 to 75 percent of field capacity for 6 months then soil properties measured at the end of sixth month. The α and n parameters of van Genuchten model using RETC software, pore size distribution and Dexter Sp value using soil moisture curve data were calculated. Application of straw at the rates of 1 to 5%, significantly increased mean weight diameter (MWD) of aggregates from 87.5 to 358.3 and 27.87 to 104.92%, saturated hydraulic conductivity from 22.94 to 195.41 and 80 to 162.58%, available water capacity (AWC) from 16.27 to 105.7 and 10.94 to 96.35%, n parameter from 4.5 to 21.8 and 1.74 to 8.14% and Sp from 32.61 to 73.91 and 5.62 to 38.2% and decreased α parameter from 12.67 to 59.15 and 25 to 45% in sandy loam and clay loam soils, respectively. Consequently, improving effects of straw at the used rates on the sandy loam soil was more observable than clay loam soil.