Changes in soil organic carbon stock and nutrient status after conversion of pasture land to cultivated land in semi-arid areas of northern Ethiopia

Conversion of native pasturelands to cultivated land led to a decline in soil fertility resulting in low agricultural productivity. This study attempted to investigate the magnitude and rate of pastureland to cultivated land conversion and the associated impact on selected soil properties. The study was conducted in three villages of Ofla district, northern Ethiopia. Land-use conversion that happened between 1973 and 2015 was investigated using satellite images supplemented by field observation and key informant interview. Cultivated lands with different history of cultivation period (2, 10, 20, 30 and 42 years) since conversion were identified. A total of 54 soil samples were collected from cultivated and pasture lands for soil physico-chemical analysis. Results showed that pastureland conversion to cultivated land increased at a medium rate of 17 ha year(-1) and by 46% over the last 42 years. Over the same period, soil organic carbon, total nitrogen, available phosphorous, available potassium and electrical conductivity declined by 65%, 59%, 57%, 70% and 74%, respectively. The continued steady decline in soil quality with increasing period of cultivation shows that the current management practices are not sustainable and calls for urgent solution to reverse the negative scenario.