Soil Organic Carbon and Total Nitrogen Stock Dynamics in the Enset Dominated Farming System of Southwestern Ethiopia

Abstract

The study was aimed to investigate soil organic carbon (SOC) and total nitrogen (TN) dynamics among different land use systems in the Essera district of Dawuro zone, southwestern Ethiopia. Landscape of the district was dominantly covered with enset (Ensete ventricosum) farming system. For this study, three representative land use types namely, Enset farm, woody and cultivated lands were considered. For each land uses, a plot of 25x25m size was marked as a sample plot to collect soil samples in an‘X’ design (from the middle and four corners of the plot). Accordingly, both composite and core sampled soils were gathered from the five subsequent soil depths (i.e.0-5, 5-10, 10-15, 15-20 and 20-25cm). Consequently, analysis of variance was conducted by using SAS version 9.2. Moreover, a mean separation for each parameter was made using LSD (Least Significant Difference) test. The result confirmed that soil organic carbon (SOC) and total nitrogen (TN) stocks were significantly influenced by topographic variation, land use types and soil depths. The highest SOC and TN stocks were observed in the lower slope position, enset farm land and upper soil depths. Regarding to land use difference, 18.65 and 13.50 t/ha SOC stock were observed in the enset and cultivated farm land respectively. TN was also highest in the enset farm land as compared with cultivated and woody land. In contrast, the lowest soil organic carbon stocks were recorded in the upper slope position of cultivated land and lower soil depths. Both SOC and TN stocks were significantly decreased from the upper soil layers to lower soil depths. Soil physical properties were also significantly influenced by topographic position, land use difference and soil depths. Soil clay contents were highest in the enset and woody land while lowest in the cultivated land. However, soil bulk density, soil silt and sand fractions were highest in the cultivated land. Moreover, soil clay content was significantly increased from upper to lower slope position and vice versa for soil bulk density, soil silt and sand fraction. In conclusion, based on the confirmed result, it deserves to improve soil fertility management under different land use types and slope categories, so that soil organic carbon, total nitrogen and soil clay contents could be improved accordingly.