Conservation agriculture (CA)

What is conservation agriculture?

The Food and Agriculture Organization (FAO) of the United Nations define conservation agriculture, or CA, as:

'a farming system that can prevent losses of arable land while regenerating degraded lands. It promotes maintenance of a permanent soil cover, minimum soil disturbance and diversification of plant species. It enhances biodiversity and natural biological processes above and below the ground surface, which contribute to increased water and nutrient use efficiency and to improved and sustained crop production.'

CA systems have three key components.

  • The soil is not disturbed by cultivation, or such disturbance is minimised. This might be done by direct planting of a crop through the stubble of the previous one. Alternative methods to cultivation are needed to control weeds.
  • The soil is protected with an organic mulch, typically the residues of the previous crop. As well as protecting the soil against the erosive effects of rain, this can enhance the organic carbon content of the soil and so its biological activity.
  • The cropping system is diversified to reduce effects of pests and diseases. This may be done by crop rotation or by intercropping.

Conventional and CA maize plots at Chitedze Experimental Farm, Malawi

Why use CA?

Climate change makes it increasingly challenging to sustain and improve agricultural productivity in sub-Saharan Africa while protecting land and water resources. Conservation agriculture, which is attracting a lot of interest in Africa, is one strategy to achieve this.

Is CA the solution in all respects?

Although there is evidence that CA has the potential to improve crop yields and their resilience under climate change, it cannot be offered as a panacea. Its adoption has different labour demands to those of traditional cultivation and increased use of herbicides. There may also be competing uses for the mulching materials (animal feed, fuel). Furthermore, our understanding of the soil under CA is limited, which makes it hard to predict when and where CA will be successful. For example, how do CA practices change the soil's structure and the behaviour of soil water? Does this improve storage of water in the soil? What are the implications for groundwater resources under CA? The CEPHaS project aims to address some of these key knowledge gaps.

Importantly, the evaluation of CA requires cross-disciplinary input. Part of this must be an evaluation of the extent to which CA can be expected to be more resilient than traditional cultivation under climate change.

Further reading on CA:

Food and Agriculture Organization of the United Nations

African Conservation Tillage Network

UK Research and Innovation Global Challenges Research Fund

CEPHaS is funded by Research Councils UK through its Global Challenges Research Fund programme.

British Geological Survey Rothamsted Research Liverpool School of Tropical Medicine The University of Nottingham The University of Zambia Lilongwe University of Agriculture and Natural Resources The University of Zimbabwe Kasisi Agricultural Training Centre Zambia Agriculture Research Institute Department of Agricultural Research Services