Effect of land use on physical and chemical parameters of soil and sediment in Qarnave and Yelcheshme watersheds, Golestan Province, Iran

The objective of this investigation was assessment of physical and chemical parameters of soil and sediment in loess lands under different land uses, in the north of Iran. A yearly soil sampling was carried out randomly in three land uses (cultivated, forest and pasture) in Qarnave and Yelcheshme watersheds. Sediment samples were taken monthly in the watersheds at the hydrometrical station of Tamer located in downstream of the watersheds. The results showed that soil texture was silty clay loam and silty loam in forests and cultivated lands, respectively. In both watersheds, the highest amount of pH, carbonate calcium, available phosphorus (P) and bulk density (BD) was observed in cultivated lands, whereas the highest amount of total nitrogen (TN), mean weight diameter (MWD) and organic carbon (OC) was observed in forest. The highest amount of TN was observed in autumn, whereas the maximum amount of K was observed in summer, in both soil and sediment samples. The highest amount of P in soil and sediment was observed in summer and winter respectively. Also, the highest percentage of OC in soil and sediment was observed in autumn and summer respectively. The results showed that tillage and soil cultivation in cultivated lands may lead to reduction of OC and BD, therefore, decreasing the MWD.