Soil Carbon and Agricultural Productivity: Perspectives from Sub-Saharan Africa - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 132

10 Soil Carbon and Agricultural
Productivity: Perspectives from
Sub-Saharan Africa

Andre Bationo*, Boaz S. Waswa and Job Kihara

Abstract
Soil carbon plays a key role in maintaining crop productivity in the soils in sub-Saharan Africa (SSA).
This is more so considering that most smallholder farmers cannot afford the use of adequate amounts
of inorganic fertilizers to restore the proportion of nutrients lost through crop harvests, soil erosion
and leaching. Complicating the situation is the huge proportion of land under threat of degradation in
the form of soil erosion and nutrient decline. There are numerous opportunities for improving soil
carbon as a basis of ensuing sustainable agriculture. This paper discusses the role of soil carbon in
agricultural production, with special focus on sub-Saharan Africa. First, the paper presents a discus-
sion on the functions of soil carbon (biological, chemical and physical). This is followed by a look at
the causes of carbon variation across agroecosystems. Management of soil carbon and productivity is
evaluated in the context of resource availability, quality and soil organic matter pools. Drawing from
the integrated soil fertility management practices in Africa, the paper discusses various strategies for
organic carbon management and the implication of the same on crop productivity and soil properties.
A special focus is given to the lessons learned from long-term experiments across Africa.

Introduction

(plant residues) and losses, mainly micro-
bial decomposition and associated mineral-
ization. This amount will vary with factors
such as the specific land use undergoing
change, soil type and texture, soil depth,
bulk density, management and climate. The
decrease of organic matter in topsoils can
have dramatic negative effects on the water-
holding capacity of the soil, on structure
stability and compactness, nutrient storage
and supply, and on soil biological life such
as mycorrhizas and nitrogen (N)-fixing bac-
teria ( Sombroek et al ., 1993).

Managing soils so that carbon stocks are
sustained and even enhanced is of crucial
importance in ensuring sustainable crop
production. Soil organic carbon (SOC) is
considered as the most important indicator
of soil quality and agronomic sustainability.
It is the main constituent of soil organic
matter (SOM). Organic matter impacts on
the physical, chemical and biological prop-
erties of soils. The amount of carbon in a soil
is influenced by the balance between inputs