Challenges to increasing the soil carbon pool of agro-ecosystems in China

LIN Er-da, GUO Li-ping, JU Hui

Institute of Environment and Sustainable Development of Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081,P.R.China

1. China is party to the Paris Agreement that aims to mitigate climate change global warming to under 2 degrees

On December 12, 2015, at the United Nations Framework Convention on Climate Change (UNFCCC) 21st Conference of the Parties (COP21) in Paris, France, 195 parties around the world have adopted the Paris Agreement, to ensure that the global average temperature rise does not exceed 2 degrees. Before the climate conference in Paris, more than 180 countries, including China, submitted mitigation related documents (Xinhua 2015), such as actions and policy measures including agricultural adaptation measures to achieve climate change goals. If the average temperature rise is near or above 2 degrees, climate change will greatly increase the uncertainty of agricultural production, and threaten food security.

2. Control of agricultural greenhouse gas(GHG) emissions should be incorporated into China’s climate change strategy

Agricultural ecosystems are not only the victims of climate change and extreme events (Smithet al.2014), but are also emitters of GHG such as N2O and CO2. The National Inventory of greenhouse gases did not give estimates of direct emissions from soils due to some uncertainties (Yuet al.2007; NDRC 2014). In 2007, non-CO2greenhouse gases accounted for 13% of Chinese total GHG emissions(NDRC 2014). As they form a large part of total emissions,the control of agricultural greenhouse gas emissions should be incorporated into the national climate change strategy as soon as possible (Xinhua 2015).

3. The 4‰ initiative for increasing the soil carbon pool to offset national greenhouse gas emissions from fossil fuel combustion

At the end of the 2015 UN Climate Conference in Paris, the French Minister of Agriculture put forward an international initiative called the “4‰ initiative: Soils for food security and climate” which aimed to show that achieving food security and combating climate change are complementary, and to ensure that agriculture provide solutions to climate change.This initiative consists of a voluntary action plan under the Lima Paris Agenda for Action (LPAA), and is backed up by a strong and ambitious research program (Minasny 2015;UNFCCC 2015 ).

The “4 per 1 000” Plan is based on the global amount of organic carbon stored in 2-m deep soil of 2.4 trillion tons,and the current global fossil fuel emissions from combustion of about 8.9 billion tons of carbon equivalent, which is equivalent to 4‰ of global reserves of soil organic carbon.This means that global fossil fuel emissions can be offset by increasing world soil organic carbon reserves by 4‰ each year. The “4 per 1 000” Plan is beneficial for global food security by improving the soil organic matter content and is a key support to mitigate climate change (Sunet al.2010;Milneet al.2015). Therefore, the project can be thought of as an ambitious plan for the sustainable development of the world.

The plan calls for an average increase in soil carbon of 0.6 tons per ha per year for the 149 million square kilometers of global land used by the global population of 7.5 billion for producing enough food, to offset the global fossil fuel combustion emissions of greenhouse gases (Minasny 2015 ).

A recent study suggested that from 1985 to 2006 in China,the surface soil organic carbon (0–20 cm) increased by an average of 25.5 Tg yr–1, about 0.2 tons per ha, only one third of the 0.6 t ha–1yr–1was needed to offset greenhouse gas emissions from fossil fuel combustion (Panet al.2010;Chenget al.2013). Further, on non-cultivated land, there is likely to be little or no increase in soil carbon.

China therefor faces big challenges to achieve this initiative. An integrated use of straw technology may be used more widely to improve soil carbon sequestration, and other opportunities include improved fertilizer use efficiency and greenhouse gas mitigation through the waste management project under construction in China.

4. Enhancing resilience of agricultural ecosystems

This paper suggests that China may put forward the biomass treatment centered high yield and fertilizer-carbon sequestration project to enhance resilience of agroecosystems to climate change. Enhancing the capacity of irrigation to increase production and improvement of soil fertility are two important measures to ensure agricultural resilience. Since 2005, the Ministry of Agriculture of China has implemented a soil testing and fertilizer project (MOA 2009) called the “Soil Organic Matter Increase Subsidy Project” across the country (Luet al.2009; MOF 2016),that supports farmers returning straw to the soil, planting green manure crops, and increasing organic fertilizer application. It is expected to run for 20 years, and increase soil carbon sequestration of farmland over the whole country to 0.6 to 1 Pg, namely an increase of 30–50 Tg per year on average, equivalent to 0.25–0.4 t ha–1annual carbon sequestration (Panet al.2010). If implementation of the project increases the amount of straw returned to soil, and at the same time, incorporates the use of organic fertilizer containing more beneficial microorganisms, and other manure and technologies such as soil conditioner, the soil carbon sequestration rate may reach 80 Tg yr–1, or 0.6 t ha–1.

In the long run, improved farmland management and restoring degraded land are key measures to promote agricultural ecosystem productivity and resilience. If more crop straw can be returned into soil and become soil organic carbon, the system resilience will be enhanced.

Acknowledgements

The authors thank financial supports from the National Natural Science Foundation of China (41675115), the National Key Research and Development Programof China(2017YFD 0300301, 2017YFD0200106) and the Agricultural Science and Technology Innovation Program of Chinese Academy of Agricultural Sciences.

Cheng K, Zheng J, Nayak D, Smith P, Pan G, 2013. Reevaluating biophysical and technologically attainable potential of topsoil carbon sequestration in China’s croplands.Soil Use and Management, 29, 501–509.

Lu F, Wang X, Han B, Ouyang Z, Duan X, Zheng H, Miao H. 2009. Soil carbon sequestrations by nitrogen fertilizer application, straw return and no-tillage in China’s cropland.Global Change Biology, 15, 281–305.

Milne E, Banwart SA, Noellemeyer E, Abson D, Ballabio C,Bampa F, Bationo A, Batjes N, Bernoux M, Bhattacharyya T, Black H,Buschiazzo D, Cai Z, Cerri C, Cheng K,Compagnone C, Conant R, Coutinho H, Zheng J. 2015.Soil carbon, multiple benefits.Environmental Development,13, 33–38.

Minasny B. 2015. 4 per 1000: Soil carbon to mitigate climate change. [2016-10-16]. http://sydney.edu.au/news/agriculture/1272.html?newsstoryid=15532

MOA (Ministry of Agriculture, China). 2009. Soil testing formula fertilization realizing a complete coverage of the county area this year. [2009-10-30]. http://www.moa.gov.cn/ztzl/ctpfsf/gzdt/200910/t20091009_1361972.htm (in Chinese)

MOF (Ministry of Finance, China). 2016. In 2016, the central government allocated 1 billion CNY to support to carry out the integrated utilization experiment of crop straw. [2016-06-10].http://czzz.mof.gov.cn/caijingzixun/caijingxinwen/201605/t20160530_2058692.html (in Chinese)

NDRC (National Development and Reform Commission, China).2014. The People’s Republic of China on the second national information bulletin of climate change. [2014-06-15]. http://qhs.ndrc.gov.cn/zcfg/201404/t20140415_606980.html (in Chinese)

Pan G, Xu X, Smith P, Pan W, Lal R. 2010. An increase in topsoil SOC stock of China’s cropland between 1985 and 2006 revealed by soil monitoring.Agriculture,Ecosystems and Environment, 136, 133–138.

Smith P, Bustamante M, Ahammad H. 2014. Agriculture,forestry and other land use (AFOLU). In:Climate Change 2014:Mitigation of Climate Change.Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Sun W, Huang Y, Zhang W, Yu Y. 2010. Carbon sequestration and its potential in agricultural soils of China.Global Biogeochemical Cycles, 24, 1302–1307.

UNFCCC (United Nations Framework Convention on Climate Change). 2015. Join in the 4/1000 initiative: Soils for food security and climate. [2015-12-30]. http://newsroom.unfccc.int/lpaa/agriculture/join-the-41000-initiative-soils-for-foodsecurity-and-climate/

Xinhua. 2015. Authorized distribution: improved action on climate change - China national independent contribution. [2015-07-8]. http://news.xinhuanet.com/2015-06/30/c_1115774759.htm (in Chinese)

Yu D S, Shi X Z, Wang H J, Sun W X, Warner E D, Liu Q H.2007. National scale analysis of soil organic carbon storage in China based on Chinese soil taxonomy.Pedosphere,17, 11–18.