Review and meta-analysis of organic matter in cultivated soils in southern Africa

Abstract

Soil organic matter (SOM) is tightly linked to soil quality, but cultivation generally causes a rundown of SOM, reducing soil quality and releasing carbon dioxide into the atmosphere.Internationally, countries are expected to reduce their greenhouse gas (GHG) emissions, and compile and update GHG inventories. Many developing countries, such as those in southern Africa, do not have reliable information regarding SOM levels in cultivated soils, changes over time and best management practices to maintain or even restore SOM. A review was conducted to collate published research on SOM [or its indicator elements, carbon (C) and nitrogen] in cultivated fields in southern Africa. A total of 84 publications were assessed, and information such as date, location, SOM/soil organic carbon (SOC) content, clay and key findings were recorded. The spatial distribution of these studies is very unequal, and focused on the central maize producing areas of South Africa. Analysis of the data shows an average SOC of 0.7 % in low rainfall areas, and up to 2.5% in higher rainfall areas. A 2 rundown of 46% of SOC due to cultivation was representative for all cultivated fields in southern Africa (R 2 = 0.84). Research gaps include understanding C sequestration and GHG emission dynamics under various management systems and for different climatic regions, which are important from a soil quality perspective as well as for inventory purposes; to help understand how field crop production can play a role in mitigating climate change; as well as a lack of multi-institutional collaboration and facilities.

Responses of soil carbon sequestration to climate‐smart agriculture practices: A meta‐analysis

“…Jien and Wang (2013) suggest that CSA management practices can potentially enhance soil water retention by improving soil porosity and erosion control. Irrigation ensures sufficient water for plant growth, resulting in more biomass production than in rainfed conditions (Capowiez et al, 2009;Chan, 2004;Shipitalo, Edwards, Dick, & Owens, 1990;Swanepoel, Laan, Weepener, Preez, & Annandale, 2016). The crop root density is much higher in irrigated conditions compared to rainfed conditions (Jobbágy & Jackson, 2000), leading to higher organic matter input.…”

The 4 per 1000 goal and soil carbon storage under agroforestry and conservation agriculture systems in sub-Saharan Africa

“…Due to an increasing demographic pressure and associated food demand, many native grassland and forest areas have been converted to croplands, and soils have experienced a massive decline in SOC, mainly as a result of low carbon inputs into soil, and topsoil erosion (Agbenin and Goladi, 1997;Solomon et al, 2002;Lemenih et al, 2005;Zingore et al, 2005;Kintché et al, 2010;Moebius-Clune et al, 2011). For example, from a review of published research it was estimated that SOC in croplands in southern Africa has declined by 25 to 53% (Swanepoel et al, 2016). Other studies (e.g.…”

Impacts of Socio-Psychological Factors on Actual Adoption of Sustainable Land Management Practices in Dryland and Water Stressed Areas

“…Subsequently, a location-based specific study is often necessary to understand the real factors that prevent farmers from adopting productivity-enhancing technologies and agricultural practices. In addition to this, farmers' decisions to adopt technological innovations depend on multiple and interrelated factors [17]. Considering this, additional empirical evidence is therefore still needed to understand what motivates smallholder farmers to adopt technologies and improved agricultural practices [18].…”