Cropping systems, carbon sequestration and erosion in Brazil, a review

Abstract

Soils represent a large carbon pool, approximately 1500 Gt, which is equivalent to almost three times the quantity stored in terrestrial biomass and twice the amount stored in the atmosphere. Any modification of land use or land management can induce variations in soil carbon stocks, even in agricultural systems that are perceived to be in a steady state. Tillage practices often induce soil aerobic conditions that are favourable to microbial activity and may lead to a degradation of soil structure. As a result, mineralisation of soil organic matter increases in the long term. The adoption of no-tillage systems and the maintenance of a permanent vegetation cover using Direct seeding Mulch-based Cropping system or DMC, may increase carbon levels in the topsoil. In Brazil, no-tillage practices (mainly DMC), were introduced approximately 30 years ago in the south in the Paraná state, primarily as a means of reducing erosion. Subsequently, research has begun to study the management of the crop waste products and their effects on soil fertility, either in terms of phosphorus management, as a means of controlling soil acidity, or determining how manures can be applied in a more localised manner. The spread of no-till in Brazil has involved a large amount of extension work. The area under no-tillage is still increasing in the centre and north of the country and currently occupies ca. 20 million hectares, covering a diversity of environmental conditions, cropping systems and management practices. Most studies of Brazilian soils give rates of carbon storage in the top 40 cm of the soil of 0.4 to 1.7 t C ha-1 per year, with the highest rates in the Cerrado region. However, caution must be taken when analysing DMC systems in terms of carbon sequestration. Comparisons should include changes in trace gas fluxes and should not be limited to a consideration of carbon storage in the soil alone if the full implications for global warming are to be assessed. no-tillage / mulch / stocks / fluxes / greenhouse gas / Brazil

Greenhouse gas mitigation options in Brazil for land-use change, livestock and agriculture

“…ii) A mean rate of soil organic carbon (SOC) storage derived from the studies of Bernoux et al (2006) and Bayer et al (2006), which represent the rate in the top 20cm of the soil profile for the South and Central (Cerrado) regions of Brazil; iii) The adoption of NT implies in changes in farming practices (Snyder et al, 2009(Snyder et al, ) such *2008(Snyder et al, -2012(Snyder et al, and 2013(Snyder et al, -2017 correspond respectively to the 1 st and 2 nd commitment periods under the Kyoto Protocol (even though Brazil is not subject to Quantified Emission Reductions, it is a useful comparison parameter). BAU: Business as Usual.…”

“…All those considerations highlight that mitigating GHG emissions is a great challenge for Brazil itself, but with worldwide importance. Concomitantly with the emissions, Agriculture and LUCF are also able to remove CO 2 from the atmosphere depending on the land conversion (e.g., abandonment of managed lands) and management (Bernoux et al, 2001(Bernoux et al, , 2006Cerri et al, 2004Cerri et al, , 2007. Thus, the objective of this study is to review and calculate the potential of mitigation strategies (decreasing emissions and enhancing sinks) in Brazil for the Agricultural and LUCF sectors, both considering already foreseen strategies and proposing new options.…”

Texture and organic carbon contents do not impact amount of carbon protected in Malagasy soils

“…The management and enhancement of soil organic carbon (SOC) is very important for agriculture (fertility) as well as for the environment (carbon sequestration), mainly in tropical regions (Bernoux et al, 2006; where development, food security, adaptation and mitigation have to be promoted in synergy . Three main mechanisms of SOC protection in soil exist: (i) biochemical stabilization, (ii) chemical stabilization and (iii) physical protection (Six et al, 2002).…”

Ex-ante greenhouse gas balance of agriculture and forestry development programs

“…Many of the technical options are readily available (Bellassen et al, 2010;Bernoux et al, 2006;Cerri et al, 2004Cerri et al, , 2007Henry et al, 2009) and could be deployed immediately: reducing emissions of carbon dioxide (CO 2 ) through the reduction of the rate of deforestation and forest degradation, adoption of improved cropland management practices (reduced tillage, integrated nutrient and water management); reducing emissions of methane and nitrous oxide through improved animal production, improved management of livestock waste, more efficient management of irrigation water on rice paddies, improved nutrient management; and, sequestering carbon (C) through conservation farming practices, improved forest management practices, afforestation and reforestation, agroforestry, improved grasslands management and restoration of degraded land. According to the Intergovernmental Panel on Climate Change (IPCC) the total technical mitigation potential of agriculture (considering all gases and sources) is estimated to be in the range 4.5 and 6 Gt CO 2 -eq per year in 2030 (IPCC, 2007;Smith et al 2007a, b).…”