Carbon footprint of smallholder rain-fed sorghum cropping systems of Kenya: A typology-based approach

Abstract

Agricultural ecosystems are the main sources of soil-atmosphere exchange (methane-CH₄, Carbon dioxide-CO₂ and Nitrous oxide -N₂O) in sub-Saharan African countries, including Kenya. To feed the ever-growing population, there is a need to identify agricultural management practices to increase food production while reducing GHG emissions for climate change mitigation and adaptation. This study aimed to estimate the GHG balance at the farm scale and identify environmental hotspots and mitigation opportunities among smallholder sorghum farms in Western Kenya. The study hypothesized that different intensification levels influenced the GHG balance. The study collected data from 300 smallholder farms in western Kenya. The principal component analysis and hierarchical clustering analysis were used for farm typologies construction. Five farm types were constructed that ranged from no or minimal external inputs and highly intensified, small to large, and low to highly endowed in tropical livestock units. The Cool Farm Tool Excel program model was used to estimate GHG balances. that the sorghum cropping systems were net sinks of soil GHGs. The GHG balance, carbon footprint, and monetary footprint significantly varied across the farm types at p = 0.025, p = 0.018, and p = 0.004, respectively. The GHG balance ranged from – 818.76 kg CO2 eq. ha⁻¹ in manure-intensive and low fertilizer-intensity small farms to 174.29 kg CO₂ eq. ha⁻¹ in fertilizer-intensive and moderate manure application rates on small farms. Fertilizer production and direct and indirect emissions (fertilizer application) were the environmental hotspots accounting for 63 and 30 % of the GHG emissions. The carbon and monetary footprints ranged from -1.29 to 0.45 kg CO₂ eq. kg sorghum ⁻¹ and -2.02 to 0.13 kg CO₂ eq. US$⁻¹ generated, respectively. The study established that sorghum cropping systems in Kenya produced limited greenhouse gas emissions.