Özet:

Sediment-bound soil nutrient loss under simulated rainfallAbstract: Soil erosion is not only the loss of soil particles, but also the loss of sediment-bounded nutrients and elements. One the principle methods of the assessment of soil erosion and nutrient loss, is to use rainfall simulators. The aim of this study was to evaluate the role of land-use, slope gradient and direction on the loss of soil nutrients in Kechik Coupled Watershed Site in Golestan Province using rainfall simulation. In order to determine the sediment’s content of potassium, nitrogen and phosphorous, flame photometry, Kjedalhl and spectrophotometry methods were used. To estimate organic carbon, the Walkey-Black method was exercised. Given the results, the highest obtained values of nitrogen loss was attributed to the agricultural land-use. This follows rangeland and forest; although, with a slight difference. Potassium loss was greatest in the rangelands by 0.15 t.ha-1, and agriculture and forest ranked second and third. Soil nutrient loss in terms of phosphorus, was maximum in the forest land-use and then respectively, agriculture and rangelands. Soil organic carbon loss was maximally measured in the forest, rangeland and agriculture, respectively. In this study, two slope classes of 0-20 and 20-40 was considered in the forest and rangeland land-uses, while the classification of slope gradient in agricultural land-use was in different two classes of 0-15 and 15-30. According the findings, soil nitrogen, phosphorus and organic matter loss was highest in case of the second slope gradient class (20-40% in rangelands and agricultural fields; 20-40% in forest land-uses) of all land-uses and aspects. Interestingly, soil potassium loss was greatest in the first slope class. Northern slope directions had the highest soil nutrient loss compared with the southern direction in all land-use types. The findings of this study put emphasis on the land-use management and primarily underlines the role of agricultural land-uses.

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