농업 분야의 온실가스 배출을 줄이기 위한 방법들

무경운 농법을 위한 정책 변경의 동력과 혜택

관행적인 경운에 기반한 농업은 주로 농민들이 잡초를 통제하기 위한 수단으로 개발되었다. 그러나 그 방법은 흙을 물과 바람에 의한 침식에 취약하게 만들고, 유실이 증가하며, 토양의 생산성을 떨어뜨리고, 흙을 뒤집어엎고 농기계의 연료를 태움으로써 온실가스를 배출한다. 무경운 농법 -이전 작물의 부산물 아래에 직접 씨앗을 심음- 은 기계적인 토양 교란을 최소화하고, 유기물로 영구적인 토양 덮개를 제공하며 재배하는 작물의 종을 다양화함으로써 이 과정을 완전히 바꾼다(FAO, 2013a).

The financial benefits of no-till practices can be considerable, but depend on the location. Farmers save between 30–40 percent of time, labour and fossil fuel inputs using no-till practices, compared to conventional tillage (FAO, 2001; Lorenzatti, 2006). In Argentina it was found that one litre of fuel was needed to produce 50 kg of grain under conventional tillage, but it could produce 123 kg under no- till practices (Lorenzatti, 2006).

Climate adaptation benefits can also be significant. While Kazakhstan’s 2012 drought and high temperatures halved wheat yields overall, wheat grown under no-till practices were more resilient, producing yields three times higher than conventionally cultivated crops (FAO, 2012). 

Although no-till practices have only a small effect on reducing methane or nitrous-oxide emissions (Smith et al., 2008), a number of studies show the significant potential of no-till cultivation to sequester carbon. The expansion of Brazil’s no-tillage system under its National Plan for Low Carbon Agriculture (ABC Plan), for example, may build up an additional 500 kg per hectare and year of soil organic carbon, offsetting a total of 16–20 MtCO2e by 2020, equivalent to 1.6–2.0 MtCO2e per year. Kenya anticipates an increase in carbon uptake of 1.1 MtCO2e by 2030, equivalent to 0.04 MtCO2e per year, from no-till farming activities under its Climate Change Action Plan (Stiebert et al., 2012). In China, no-till farming may sequester a total of 2.27 MtCO2e of soil carbon by 2015, equivalent to 0.5MtCO2eperyear(Chengetal.,2013a).Theseareallestimates of the potential to mitigate greenhouse gas emissions; estimates of what has already been achieved are given in the next section.

Policies that work

Governments have traditionally encouraged no-till practices as a measure to curtail soil erosion, and have only recently begun to promote it as a way to mitigate greenhouse gas emissions. However, farmers face difficult challenges during the transition to no-till practices related to high investment costs for machinery, increased dependence on such herbicides as glyphosate, changes in production inputs, and differences in crop and cover-crop management2. Thus, support is required for farmers during the transition.

In 2011 Brazil established its ABC Plan, the first national policy promoting no-till cultivation, which includes state-level activities, based upon local and sub-national government plans3. It sets implementation goals, anticipating that adoption of no-till practices increase from 31 million hectares to 39 million hectares under the plan. Farmers have access to ABC Plan credit and finance as well as training and extension services if management practices are compliant with the approach.

The adoption of no-till practices in Brazil was brought about by many factors: new knowledge on no-till systems stemming from research by the Brazilian Agricultural Research Corporation; support from farmer associations such as the Brazilian Federation of Direct Planting and Irrigation; backing from agricultural machinery companies who recognize the potential benefits from promoting the technology and expanding their markets; and recognition by farmers that no-till practices bring increased land productivity and reduced production costs (Casão Junior et al., 2012).

Between 1982 and 1997 overall cropland erosion dropped by more than a third in the USA, where policy interventions to promote no-till practices on highly erodible land contributed up to 62 percent of the overall reductions (Claassen, 2012)4. 

Classifying soils as highly erodible made it easier to target specific areas for conversion to no-till cultivation, enabled by financial support from the United States Department of Agriculture. To get this support, farmers on highly erodible lands, approximately 25 percent of all USA cropland, had to devise and have approved a soil conservation plan. As a result, in 2009, 35 percent of USA cropland, mostly producing soy, was under no- or reduced-tillage, although often not permanently, which reduces its effectiveness to sequester carbon.

No-till agriculture increased in Australia from 9 percent of cropland in 1990 to 74 percent in 2010 (Llewellyn and D’Emden, 2010), particularly in grain producing areas. Awareness of soil erosion problems, region-specific information and learning opportunities for farmers, and declines in the price of glyphosphate, all contributed to the adoption of no-till practices (D’Emden, et al., 2006; Llewellyn and D’Emden, 2010). Australia’s Landcare Programme, a community-based approach to land management, which is now made up of 6 000 farmer groups across the country, has played a key role in information dissemination and technical support (Department of Agriculture, 2013). The programme provides a refundable tax offset, financed by carbon-tax revenues, of 15 percent of the purchase price of an eligible no-till seeder to participating farmers. More recently, Australia has recognised the greenhouse gas reduction potential of no-till practices by including them in its Carbon Farming Futures programme – part of Australia’s  Clean Energy Future Plan, and central to the cropland management component of Australia’s national greenhouse gas-reduction target.

Chinese interventions to increase the use of no-till practices have aimed to reduce soil erosion, treat crop residue, and eliminate their post-harvest burning.5 Up to now, reducing greenhouse gas emissions has not been a factor. As in much of Asia, smaller farm sizes restricted adoption of no-till practices. In addition, crop residues were commonly used for alternative purposes, such as feed for livestock (Lindwall and Sontag, 2010). China hopes to expand no-till practices to 13.3 million hectares by 2015 (Ministry of Agriculture, 2009), especially by providing subsidies to farmers (Zhao, et al., 2012).

No-till practices have spread across diverse soil types and agricultural production systems around the world over the last 30 years. The MERCOSUR countries of Argentina, Brazil, Paraguay and Uruguay have the highest rates of no- till cultivation, covering 70 percent of total cultivated area, two-thirds of which are under permanent no-till schemes, resulting in significantly increased soil carbon storage (Derpsch et al., 2010). Table 4.1 shows the cumulative mitigation benefits of up to 240 MtCO2e of avoided emissions in selected countries based on annual greenhouse gas mitigation rates in different climatic zones as provided in Smith et al. (2008) and best-available information on the coverage of no-till cultivated areas6.

 

http://www.unep.org/publications/ebooks/emissionsgapreport2013/portals/50188/EmissionsGapReport%202013_high-res.pdf