Soil Organic Carbon Stocks under Different Land Utilization Types in Western Kenya

Abstract

The up-surging population in sub-Saharan Africa (SSA) has led to the conversion of more land for agricultural purposes. Resilient land utilization types that input carbon to the soil are key in enhancing climate change mitigation. However, there are limited data on different land utilization types’ contribution to climate mitigation through carbon input to soils. The study aims to quantify carbon stock across different land utilization types (LUT) practiced in Western Kenya. The following land utilization types were studied: agroforestry M (agroforestry with Markhamia lutea), sole sorghum, agroforestry L (agroforestry with Leucaena leucocephalaI), sole maize, and grazing land replicated thrice. To determine soil bulk density, SOC concentration, and soil carbon stock, soil samples were collected at depths of 0–5, 5–10, 10–20, and 20–30 cm from different LUTs. A PROC ANOVA was used to determine the difference in soil bulk density, SOC, and SOC stock between different LUTs and depths. The four variables differed across the LUTs and depths. A high soil bulk density was observed at 0–5 cm under grazing land (1.6 g cm−3) and the lowest under agroforestry M (1.30 g cm−3). Conversely, the soil bulk density was low at 20–30 cm under grazing land. The 0–5 cm depth accounted for a high share of SOC and SOC stock under Agroforestry M, while the 10–20 and 20–30 cm depth accounted for the high share of SOC stock under agroforestry L. The study showed differences in SOC across the different depths and LUTs. The findings highlight that agroforestry L and agroforestry M are promising interventions toward climate mitigation through carbon induction to soils.

The Oasisization Process Promotes the Transformation of Soil Organic Carbon into Soil Inorganic Carbon

“…In the oasis transitional zone, the surface plant residues of forest land accumulate a lot, with obvious humification, and the rich litter and root exudates in the soil make its organic carbon content higher than that of other land-use types, which is consistent with the results found by Arid Rajasthan of India, in that the organic carbon in the surface soil is high [29]. In the oasis, the SOC in the cotton fields and orchards decreased with the increase in soil depth, and Esphorn and others also showed similar conclusions about the changes in organic carbon in different land-use types [30]. At 40~100 cm, compared with the forest land and waste land, the content of SOC in the cotton field obviously reduced, which is due to the frequent change in soil structure by tillage measures taken to plant crops regularly.…”