Carbon stock, sequestration and soil properties among fields in smallholder farms in southern Ethiopia

Abstract

Background: Soil organic carbon (SOC) is key indicator of soil quality and health. It has substantial benefits to the ecosystem. Information on the magnitude of carbon pools under field scale of subsistence farms is scanty. This study aimed to assess carbon stock, sequestration and soil properties among different fields in smallholder farms of southern Ethiopia. Five field types within a farm were investigated viz. coffee (Coffea arabica L.), enset (Ensete ventricosum), root and tuber crop field (RTC), crop field used for growing cereals and pulses, and fallow land. For each field, eight representative fields as a replication were selected. Surface soil samples were collected, and analyzed to determine soil physico-chemical properties. In addition, C stock, C-sequestration, and CO 2 emission were also evaluated. Results: The result regarding soil properties revealed significant differences in almost all of investigated parameters. The minimum and maximum values being recorded were: bulk density (BD) (1.05, 1.29 gm cm −3), pH (6.1, 7.0), SOC (1.1, 2.48%), TN (0.09-0.19%), available P (1.1, 70.9 mg/kg), total exchangeable bases (9.5, 20.5 Cmolc/kg), K/Mg (0.37,1.02), B (0.4, 1.2 mg/kg) Cu (0.32, 0.91 mg/kg), Zn (5, 20.5 mg/kg), Fe (105.5, 133.8 mg/kg) and CEC (18.6, 27.5 mg/ kg). Fields in the backyard (enset and coffee) showed lowest BD and maximum values of soil chemical properties. On contrary, highest BD and lowest values of chemical parameters were observed in crop and fallow fields. The result further indicated that the field that stocked and sequestered more carbon, and emitted less CO 2 was coffee > enset > RTC > crop field > fallow land. C-stock and sequestration (t/ha) magnitude was being: coffee (81.4, 298.5), enset (75.5, 277.0), RTC (68.8, 252.6), crop field (57.5, 211.0) and fallow (43.3, 159). Using coffee field as least CO 2 emitter and as the base value for comparison, the percentage increment in CO 2 emission out of the sequestered carbon was 7.2% (enset), 15.4% (RTC), 29.3% (crop field) and 46.7% (fallow).Soil deterioration index (%) relative to coffee field for OC, N, P, and K in their order was as follows: enset [

Changes in Soil Properties with Long-Term Organic Inputs Due to Distance from Homestead and Farm Characteristics in Southern Ethiopian Farmlands

“…5) across all the studied kebeles can be attributed to the application of farmyard manure, household waste and increased carbon inputs through litter fall and root turnover from perennial and annual crops (Hao et al, 2003;Shukla et al, 2006;Liu et al, 2018;Ichinose et al, 2020). Continuous organic inputs from farmyard manure and litter fall ascribed to the long years of soil amendment is likely to have played an important role in the maintenance of soil OC levels, which in turn improved soil quality and productivity (Laekemariam, 2020). In addition, higher vegetation cover Fig.…”

“…In general, the surveyed farmlands across the kebeles had low soil OC, moderate CEC, and high to very high K (EthioSIS, 2016). Low organic carbon and CEC is typical in many Sub-Saharan African soils due to climate and soil driven rapid turnover of organic carbon, soil erosion and resource poor, extractive farming practices (Kiflu and Beyene, 2013;Laekemariam, 2020;Kebebew et al, 2022). Soils in this region have inherently high K due to their volcanic origin and genesis (EthioSIS, 2016).…”

“…The management of soils in Ethiopia creates a gradient characterized by greater inputs of organic amendments close to the home where vegetables and perennial crops are grown, and fewer organic inputs further away in plots that are planted with cereals, such as teff or maize (Laekemariam, 2020). This may be confounded, to some extent, by the placing of homes where soil was initially most fertile, but it does provide a gradient of farming practices to explore the importance and impacts of organic inputs on soil carbon and nutrients.…”

Improvement of Soil Pore Distribution and Soil Moisture Content using Organic Matter Addition Technology

“…Micro pore (cm 3 /cm 3 ) 0.28 pF 0 (cm 3 /cm 3 ) 0.62 pF 1 (cm 3 /cm 3 ) 0.52 pF 2 (cm 3 /cm 3 ) 0.34 pF 4.2 (cm 3 /cm 3 ) 0.28 plantations without organic matter input (Laekemariam, 2020). Organic matter is an essential factor in soil fertility.…”