Soil fertility assessment and mapping of spatial variability at Amareganda-Abajarso sub-watershed, north-eastern Ethiopia

Abstract

Information on soil fertility assessment and mapping of arable land helps to design appropriate soil fertility management practices. Experiment was conducted at Amaregenda-Abajarso sub-watershed to assess the fertility status and mapping the spatial variability of selected soil fertility parameters. Based on land use type, soil color, altitude, slope gradient and aspect, and to a lesser extent soil management practices, the study area was divided into 8 land units (LUs). Then, a total of 24 composite surface soil samples were collected for laboratory analysis. All of the analyzed soil properties vary significantly (P < 0.01) among LUs except C: N ratio. The mean values of sand and clay fractions ranged from 67.33 (LU 8) to 43.4% (LU 3) and 40.93 (LU 1) to 12.67% (LU 8), respectively. Dominantly, sandy clay loam soil textural class was recorded. The mean soil bulk density varied from 1.15 to 1.38 g cm^-3. The lowest (6.05) and highest (6.74) values of soil pH were recorded for LUs 8 and 2, respectively. The organic matter content of soils ranged from 1.33 (LU 2) to 3.70% (LU 8). The total N content ranged from 0.09 (LU 2) to 0.30% (LU8). The available P content ranged from 9.31 (LU 8) to 19.53 mg/kg soil (LU 1). The exchangeable K content ranged from 97.48 (LU 2) to 357.70 mg kg^-1 (LU8). The highest CEC (46.6) and lowest (33.47 cmol (+) kg^-1) values were recorded in LUs 8 and 5, respectively. Exchangeable Ca and Mg ranged from 9.25 (LU 4) to 23.35 cmol (+) kg^-1 (LU 2) and 2.76 (LU 5) to 8.50 cmol (+) kg^-1 (LU 3), respectively. The highest (76.86%) and lowest (50.61%) mean values of PBS were recorded for LUs 2 and 4, respectively. The EDTA extractable Fe, Mn, Cu and Zn, in mg kg^-1, ranged from 56.03 to 96.19, 65.30 to 226.48, 1.84 to 6.19, and 1.12 to 4.34, respectively. From the total LUs, 87.5 % were low in OM; 50%, deficient in total N and Fe, 25% were deficient in Cu and Zn and 12.5% were deficient in available K and Mn. In conclusion, integrated plant nutrient management practices that use organic inputs, mineral fertilizers, and improved crop varieties that can be adapted to local farming situations should be implemented to improve and sustain productivity of cultivated land in the area.

Keywords: Wollo; Soil; Cultivation; Crops; Maps; micronutrients; Macronutrients