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Effects of Converting Wheat-Fallow and Wheat-Pea Rotation to Continuous Wheat on Soil Physical Properties Related to Soil Erodibility Factor

In order to study the effects of conversion of the current crop rotations in dry-land wheat farming to continuous wheat on soil erodibility factor in dryland agriculture, three soil series, namely, Sahand (Fluventic Haploxerepts), Rajol Abad (Typic Calcixerepts) and Darab (Calcic Haploxerepts), were selected at Maragheh and Hashtroud regions, northwest of Iran. The treatments consisted of continuous wheat cropping (T1), wheat-chickpea rotation (T2), and wheat-fallow rotation (T3) and were executed for 5 cropping seasons from autumn 2003 to summer 2008. Disturbed and undisturbed soil samples were taken from the experimental sites on June 2008. Appropriate soil physical and chemical properties such as infiltration rate (IR), wet-aggregate stability (WAS), bulk density (Db), calcium carbonate equivalent (CCE), organic carbon (OC), and texture were measured by routine laboratory methods and the K-factor was estimated using the supplied regression equation. Soil IR in T1 (2.01 cm hr-1) was significantly (p<0.05) lower than T2 (4.89 cm hr-1) and T3 (5.27 cm hr-1). Soil WAS in T3 (71.54%) was significantly (p<0.05) greater than T1 (58.89%) and T2 (59.24%). Lowest K-factor mean (2.23 x 10-3 t h MJ-1 mm-1) was obtained for T3 treatment and was significantly (p<0.05) lower than that of T1 treatment (6.81 x 10-3 t hMJ-1mm-1). The treatments did not havet any significant effect on OC, CCE, and Db. Based on the results obtained, the conversion of wheat-pea or wheat-fallow crop rotations to continuous wheat cropping system in dry-land agriculture in the regions studied may eventually lead to enhanced runoff and soil erosion and, therefore, it is not an appropriate practice.