Ethiopian agriculture has greater potential for carbon sequestration than previously estimated

Abstract

More than half of the cultivation-induced carbon loss from agricultural soils could be restored through improved management. To incentivise carbon sequestration, the potential of improved practices needs to be verified. To date, there is sparse empirical evidence of carbon sequestration through improved practices in East-Africa. Here, we show that agroforestry and restrained grazing had a greater stock of soil carbon than their bordering pair-matched controls, but the difference was less obvious with terracing. The controls were treeless cultivated fields for agroforestry, on slopes not terraced for terracing, and permanent pasture for restrained grazing, representing traditionally managed agricultural practices dominant in the case regions. The gain by the improved management depended on the carbon stocks in the control plots. Agroforestry for 6-20 years led to 11.4 Mg ha À1 and restrained grazing for 6-17 years to 9.6 Mg ha À1 greater median soil carbon stock compared with the traditional management. The empirical estimates are higher than previous process-model-based estimates and indicate that Ethiopian agriculture has greater potential to sequester carbon in soil than previously estimated.

Carbon revenue in the profitability of agroforestry relative to monocultures

“…Depending on the monoculture (Saccharum officinarum L., Zea mays L., Hordeum vulgare, Sorghum bicolor, Triticum spp., Eragrostis tef (Zucc.) Trotter Table 1 Modeled crop yields (Y) and revenues (R) for the composition of the plant species of the eight agroforestry plots (I-VIII) documented by Rimhanen et al (2016) and yields in AFSs (kg/0.2 ha/year) ( *Timber production in homegarden is estimated at 1.5 m per year (Table 2) **Jatropha plants yield estimate is 0.5 kg and revenue is $0.1 (Tables 2, 3) and Lentil culinaris), total revenue varied between $145 and $500 per 0.2 hectare. The highest revenue was obtained from sugarcane and wheat, and the lowest from lentil monoculture.…”

“…The simulated multistrata, homegarden type AFS plot sizes and vegetation were modeled by applying the empirical data of the 6-20-year old AFS plots studied by Rimhanen et al (2016). The plot area was divided into 50% food crops and 50% cash crops and timber trees, based on the study by Abele et al (2010).…”

“…In this study, we utilized data from Rimhanen et al (2016), who estimated that in Ethiopian multistrata AFSs in Sire, the average sequestration amount into soil was 1.2 Mg C ha -1 year -1 (95% CI 0.3-2) higher than in the adjacent monoculture plots. Rimhanen et al (2016) obtained the underground sequestration amounts from AFS plots that were 6 to 20 years old and with the species composition applied in the stylized plots. For aboveground carbon sequestration amounts, research by Nair et al (2009) was utilized, as there is no available plant-specific sequestration data.…”

“…Agroforestry systems (AFSs) may be able to accomplish both goals, i.e., to mitigate climate change while improving food security and the local economy. An AFS is a cropping system that includes trees and shrubs and thus sequesters more carbon into the soil and into vegetation than a monoculture farming system (Rimhanen et al 2016). Increased carbon stock can provide environmental services, social benefits, and potentially monetary benefit from the carbon market through carbon revenue.…”

“…Eight constructed 0.2 hectare AFS plots (I-VIII) based upon plant species composition data from Ethiopia's Sire(Rimhanen et al 2016) and the relative plant cover of AFSs in Southern Ethiopia(Abele et al 2010) …”