How climate-smart is conservation agriculture (CA)? – its potential to deliver on adaptation, mitigation and productivity on smallholder farms in southern Africa

Abstract

Climate resilient cropping systems are required to adapt to the increasing threats of climate change projected for Southern Africa and to better manage current climate variability. Conservation agriculture (CA) has been proposed among technologies that are climate-smart. For a cropping system to be labelled Bclimate-smart^it has to deliver three benefits: a) adapt to the effects of climate and be of increased resilience; b) mitigate climate effects by sequestering carbon (C) and reducing greenhouse gas emissions (GHG); and c) sustainably increase productivity and income. Research on smallholder farms from Southern Africa was analysed to assess if CA can deliver on the three principles of climate-smart agriculture. Results from Southern Africa showed that CA systems have a positive effect on adaptation and productivity, but its mitigation potential lags far behind expectations. CA systems maintain higher infiltration rates and conserve soil moisture, which helps to overcome seasonal dry-spells. Increased productivity and profitability were recorded although a lag period of 2-5 cropping seasons is common until yield benefits become significant. Immediate economic benefits such as reduced labour requirements in some systems will make CA more attractive in the short term to farmers who cannot afford to wait for several seasons until yield benefits accrue. The available data summarizing the effects of CA on soil organic C (SOC) and reductions in greenhouse gases, are often contradictory and depend a great deal on the agro-ecological environment and the available biomass for surface residue retention. There is an urgent need for more research to better quantify the mitigation effects, as the current data are scanty. Possible co-interventions such as improved intercropping/ relay cropping systems, agroforestry and other tree-based systems may improve delivery of mitigation benefits and need further exploration.

Behaviour of smallholder farmers towards adoption of conservation agriculture in Zimbabwe

“…There are several reasons for the delay in gaining the benefits of CA. When moving from conventional systems to CA, farmers have to learn new agronomic and land management strategies that may delay the advantages of CA systems (Thierfelder et al, 2017). Changing to no-tillage systems, with residue retention, may result in increased weed intensity and dynamics (Mashingaidze, Madakadze, Twomlow, Nyamangara, & Hove, 2012;Sharma & Singh, 2014); potential outbreak of some pests and diseases may occur in the short term if the mulching material carries pests and diseases with it (Giller et al, 2015).…”

“…The yield increments are attributed to improved physical, biological and chemical properties of soils. However, the yield benefits are realized 3-5 seasons after the adoption of CA (Thierfelder et al, 2017). The short-term yield improvements under CA are mainly due to early planting (Giller et al, 2015).…”

Weed control under conservation agriculture in dryland smallholder farming systems of southern Africa. A review

“…Soil degradation from conventional tillage practices emphasizes the importance of systems that increase soil organic matter content and improve soil structure (Johansen et al 2012;Tittonell et al 2012). The vulnerability of smallholder rainfed farming systems to erratic and reduced rainfall associated with climate change further highlights the need for farming practices that adapt to the impacts of climate change (Thierfelder and Wall 2010a, b;Thierfelder et al 2017).…”

Potential for Conservation Agriculture in the Dry Marginal Zone of Central Syria: A Preliminary Assessment

“…CA systems comprise the implementation of three interlinked principles: (i) no or minimum mechanical soil disturbance through no-till seeding and weeding; (ii) the maintenance of soil mulch cover with crop residues, stubbles and cover crops; (iii) cropping system diversification through rotations and/or associations CA. More generally, meta-analyses and reviews, such as those by [14][15][16][17][18], while highlighting some of the challenges related to CA adoption, show clear moisture-related benefits to crop growth and productivity in CA systems, particularly in semi-arid areas.…”