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South Africa is 13th on the list of highest emitters of global greenhouse gases GHG). Despite this is Africa still the smallest contributor to GHG emissions among the continents, yet the most vulnerable to the impacts of climate change. The effects will not be limited to rising temperatures and changing rainfall patterns, but also to increased severity and frequency of droughts, heat stress and floods. Agriculture is not only impacted upon by climate change but also contributes to global warming. However, not all agricultural systems have equal affect. So-called Conservation Agriculture (CA) is a farming system that promotes continuous no or minimum soil disturbance (i.e. no tillage), maintenance of a permanent soil mulch cover, and diversification of plant species. Thereby it enhances biodiversity and natural biological processes above and below the soil surface, which contributes to increased water and nutrient use efficiency and productivity, resulting in more resilient systems, and improved and sustained crop and pasture production. Conservation Agriculture is based on good agricultural practices and the practical application of three interlinked principles:
(1) Avoiding or minimizing mechanical soil disturbance involving seeding or planting directly into untilled soil, eliminating tillage altogether once the soil has been brought to good condition, and keeping soil disturbance from cultivating operations to the minimum.
(2) Maintaining year-round biomass mulch cover over the soil, including specially introduced cover crops and intercrops and/or the mulch provided by retained biomass and stubble from the previous crop or pasture.
(3) Diversifying crop and pasture rotations and sequences, adapted to local environmental and socio-economic conditions, and including appropriate nitrogen fixing legumes. These procedures will contribute to maintaining biodiversity above and in the soil, add biologically fixed nitrogen to the soil-plant system, and help avoid build-up of pest populations. The sequences and rotations of crops/pastures and cover crops will encourage agro-biodiversity as each crop will attract different overlapping spectra of microorganisms and natural enemies of pests.
The characteristics of CA make it one of the systems best able to contribute to climate change mitigation by reducing atmospheric GHG concentration. In the paper by Dr E. J. Gonzalez-Sanchez and colleagues, which was published in Soil & Tillage Research, Volume 190 of 2019, page 22 to 30, they assessed the carbon sequestration potential of CA in both annual and perennial crops, in the different agro-climatic regions of Africa. The title of their paper is: Meta-analysis on carbon sequestration through Conservation Agriculture in Africa.
The meta-analysis used by the authors showed that the annual carbon sequestration in African agricultural soils through CA could be 143 million tons of C per year or 524 million tons of CO2 per year. This figure is about 930% the current sequestration figure, which illustrates the enormous potential which agriculture in Africa has to support climate change mitigation. If South Africa is considered alone, the following figures are significant: The current number of hectares under CA is 439 000 providing an annual carbon sequestration of 0.45 million tons. The potential number of hectares in crop production is 2 936 285 which can provide an annual carbon sequestration of 2.3 million tons. The number of hectares (including pastures and between vines and fruit trees) which can be utilized by groundcover application is 230 989 which potentially can provide an annual carbon sequestration of 0.17 million tons. The total potential of carbon sequestration by CA for South Africa is thus 550% more than currently.
To put these figures in perspective: It is estimated that the total carbon emissions of the country may be between 108 and 167 million tons per year between 2025 and 2030 (say 140 million tons as an average). Thus, a carbon sequestration of 2.47 million tons is less than 2%, which may be considered insignificant. However, with conventional tilling and practices, carbon continuous to be released from soils. In addition, with nitrogen fertilizer nitrous oxide is released into the atmosphere with about 300 times the warming potential of carbon dioxide. Also, soil health continuous to decrease with negative implications to water retention, crop yields and sustainability. Bearing in mind the three interlinked principles of CA discussed above, it is of concern that the number of crop and crop/livestock farmers in SA that practices CA is still not more than about 15%!
Another perspective of importance to livestock farmers is worth mentioning: Less than 18% of SA agricultural land is suitable for crop production which means that the vast majority is veld which is only suitable for livestock farming. Well managed veld according to grazing capacity guidelines ensures adequate biomass and species composition in line with what is being strived for in CA. The potential for carbon sequestration is discussed in a document of Agri SA with the title: Implications of a Carbon tax and offset system for Agriculture in South Africa. Taking into consideration all biomes, estimates show that the annual carbon flux in and out of all veld and ecosystems is more than twice the carbon emissions from the country from all anthropogenic sources. In livestock farming, we indeed have an enormous potential, and therefore responsibility, to assisting with mitigating climate change!