Organic agriculture is a production system which avoids or largely excludes the use of synthetic fertilisers, pesticides and growth regulators. It can sequester carbon using crop rotations, crop residues, animal manure, legumes, green manure, and off-farm organic waste (Lampkin et al., 1999). It can also reduce carbon emissions by avoiding the use of fossil fuels used in the manufacture of the chemicals used to make synthetic materials.
Organic farming restricts the use of artificial fertilisers and pesticides, and it promotes the use of crop rotations, green manures, compost, biological pest control and mechanical cultivation for weed control. These measures use the natural environment to enhance agricultural productivity. Legumes are planted to fix nitrogen into soil, and natural insect predators are encouraged. Crops are rotated to renew soil, and natural materials such as potassium bicarbonate, and mulches are used to control diseases and weeds. Crop diversity is a distinct feature of organic farming. However, organic farming originated as a small-scale enterprise with operations from under 1 acre (4,000m2) to under 100 acres (0.40km2). Crop rotation, cover cropping, reduced tillage, and application of compost are varieties of methods used in organic agriculture. Organic agriculture is one of the important options of carbon sequestration which can reduce greenhouse gases.
Organic farmers use several different techniques. The most effective ones are fertilisation by animal manure, by composted harvest residues, and by leguminous plants such as (soil) cover and (nitrogen) catch crops. Introducing grass and clover into rotations for building up soil fertility, diversifying the crop sequences, and reducing ploughing depth and frequency also augment soil fertility. All these techniques increase carbon sequestration rates in organic fields, whereas in conventional fields, soil organic matter is exposed to more tillage and consequent greater losses by mineralisation. The annual sequestration rate increases up to 3.2 tonnes of CO2/ha-1 yr-1 by organic farming (Smith et al., 2007).
Historically, agriculture was organic, relying on the recycling of farm wastes and manures. Very little or negligible amounts of external inputs were applied. Sustainable farming practices and cycles evolved over centuries, integrated with livestock rearing. For instance, farmers of ancient India are known to have evolved nature-friendly farming techniques and practices such as mixed cropping and crop rotation.
Besides overcoming a tradition of recently adopted synthetic fertilisers and pesticides, the primary barriers to adoption of organic farming are the lower productivity and consequently higher prices, as well as lower produce quality in the marketplace. Greater education of farmers and the public needs to be done to show that the environmental and long-term sustainability advantages of organic agriculture are worth to the added current costs.
Advantages of organic agriculture
- Organic agriculture aims to improve soil fertility and N supply by using leguminous crops, crop residues and cover crops, to eliminate fossil fuel used to manufacture N fertiliser. The addition of the crop residues and cover crops leads to the stabilisation of soil organic matter at higher levels and increases the sequestration of CO2 into soils.
- Organic agriculture increases soil’s water retention capacity, which would enable a crop to go longer into a drought cycle assuming an initial full profile. This should provide an adaptation to unpredictable climatic conditions. Soil C retention is more likely to withstand climatic challenges and soil erosion, an important source of CO2 losses.
- Organic agriculture can contribute to agro-forestry production systems, which offer additional means to sequester carbon.
- Organic systems are highly adaptive to climate change due to the application of traditional skills and farmers’ knowledge, soil fertility-building techniques and a high degree of diversity.
- Organic agriculture as a water protector reduces water pollution due to the absence of pesticides and chemical fertilisers.
- Organic agriculture is compatible with conservation tillage, thereby enabling even greater C sequestration potential by incorporating this mitigation technology.
Disadvantages of organic agriculture
- Organic agriculture is less productive compared to intensive conventional agriculture. Consequently, the yield of highly demanding crops such as potatoes, grape fruits and horticultural crops is too low and energy input becomes relatively more on per unit of crop production bases (Smith et al., 2007).
- Quality of organic-grown produce is often lower due to insect damage, which is less in conventional agriculture with its use of pesticides.
- Highly dependent on nutrients derived from livestock.
Organic agriculture requires 28% to 32% less energy compared to conventional systems. Input costs for seed, fertiliser, pesticides, machinery, and hired labour are approximately 20% lower in a rotation that includes a legume compared with a conventional rotation system (figure 2), (Kimble et al., 2007).
In the East African Highlands, animal manure application leads to 2,820 kg ha-1 yr-1 carbon inputs with $156 per ha cost and 5.5% carbon sequestration efficiency (Woomer et al., 1998). The sequestration of one tonne of soil carbon using cattle manure requires $260, but return will increase by $1,066 (4.1 return ratio) as a result of the addition. Some experts estimate the cost of manure to be around $1,000, in which case the additional returns would almost vanish. Maize stover leads to 1,830 kg ha-1 yr-1 carbon inputs with $37 per ha cost and 5.4% carbon sequestration efficiency. The sequestration of one tonne of soil carbon using maize stover requires $374, but this application also suppresses crop yields resulting in a loss of $112 (-1.3 return ratio).
Annual global sequestration potential of organic agriculture amounts to 2.4-4Gt CO2e yr-1, and it can be improved to 6.5-11.7Gt CO2e yr-1 by using new technologies in organic agriculture (Smith et al., 2008).
Organic agriculture has lower methane and nitrous oxide emissions of 0.6-0.7Gt CO2e yr-1 in comparison to conventional agriculture, which includes the burning of crop residue (Smith et al., 2007).
Organic agriculture has a significant potential to provide on-farm energy by biogas production from slurry and compost, although this would detract from the quantities of organic material to return to the soil.
If all agriculture were organic, the elimination of nitrogen fertilisers would save substantial emissions. For example, in case of UK 1.5% of national energy consumption and 1% of national greenhouse gas emissions would be saved (Mae-Wan and Ching, 2008). Earlier studies showed that GHG emissions would be 48-66% lower per hectare in organic farming systems in Europe. The lower emissions were attributed to zero input of chemical N fertilisers, less use of high energy consuming feed stock, low input of P (phosphorus) and K (potassium) mineral fertilisers, and elimination of pesticides. However, productivity likely would be lower.
Although not limited to organic farming, the use of N from manure and compost or fixed from the air by leguminous plants has a mitigation potential that amounts to 4.5-6.5Gt CO2e yr-1 (out of 50Gt CO2e yr-1 global GHG emissions) or about 9-13% of the total GHG emissions. The mitigation is accomplished by sequestering C in soils due to intensive humus production (Smith et al., 2007). Regular applications of livestock manure can induce substantial increases in soil organic carbon over the course of a few years (Lal et al., 1998). Organic agriculture has lower N2O emissions i.e., 1.2-1.6 Gt CO2e yr-1. In organic agriculture, biomass is not burned. It reduces the N2O emissions by 0.6-0.7Gt CO2 e yr-1 in comparison to conventional agriculture (Smith et al., 2007). Organic systems are highly adaptive to climate change due to: (a) the application of traditional skills and farmers’ knowledge, (b) soil fertility-building techniques, and (c) a high degree of diversity.
Organic farming could considerably reduce the GHG emissions of the agriculture sector and make agriculture almost GHG neutral (Niggli et al., 2009). Greenhouse gas emissions due to the applications of synthetic fertilisers are estimated to be 1,000 million tonnes annually. These emissions would not occur using an organic approach. GHG emissions of agriculture would be reduced by roughly 20 per cent. Another 40 per cent of the GHG emissions of agriculture could be mitigated by sequestering carbon into soils at rates of 100kg of C ha-1 yr-1 for pasture land and 200kg of C ha-1 yr-1 for arable crops. By combining organic farming with reduced tillage, the sequestration rate can be increased to 500kg of C ha-1 yr-1 in arable crops as compared to ploughed conventional cropping systems, but as the soil C dynamics reach a new equilibrium, these rates will decline in the future. This would reduce GHG emissions by another 20 per cent. Organic farming is an important option in a multifunctional approach to climate change.
See the section about socio-economic development above.
Kimble, J.M., Rice, C.W., Reed, D., Mooney, S., Follett, R.F., and Lal, R. (2007): Soil Carbon Management, Economic, Environmental and Social Benefits. CRC Press, Taylor & Francic Group.
Lal, R., Kimble, JM, Follet, RF, and Cole, CV. (1998): The Potential of U.S. Cropland to Sequester Carbon and Mitigate the Greenhouse Effect, Ann Arbor Press, Chelsea, Michigan, USA. Lal, R, Kimble JM, Follett RF, and Stewart BA. (1998c) Soil Processes and the Carbon Cycle. CRC Press LLC.
Lampkin, N.H. (1999). Organic farming in the European Union: Overview, policies and perspectives. Pp23-30 in Organic farming in the European Union: Overview, policies and perspectives for the 21st century, proceedings of a joint EU and Austrian conference, 27-28 May (Baden/Vienna: Avalon Foundation and Eurotech Management).
Mae-Wan Ho and Lim Li Ching (2008): Mitigating Climate Change through Organic Agriculture and Localized Food Systems, ISIS Report 31/1/08.
Niggli, U., Fließbach, A., Hepperly, P. and Scialabba, N. (2009). Low greenhouse gas agriculture: Mitigation and adaptation potential of sustainable farming systems, Rev. 2. Rome, FAO, April; available at: ftp://ftp. fao.org/docrep/fao/010/ai781e/ai781e00.pdf.
Smith, P., Martino, D., Cai., Z., Gwary, D., Janzen, HH., Kumar, P., McCarl, B., Ogle S., O’Mara, F., Rice, C., Schloes, B. and Sirotenko, O. (2007): Agriculture. In climate change 2007: Mitigation. Contribution of working group III to the fourth assessment report of the intergovernmental Panel on Climate Change [B. Metz, O.R. Davidson, P.R. Bosch, R. Dave, L.A. Meyer (eds)], Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
Smith, P., Martino, D., Cai, Z., Gwary, D., Janzen, H.H., Kumar, P., Mccarl, B., Ogle, S., O’mara, F., Rice, C., Scholes, R.J., Sirotenko, O., Howden, M., Mcallister, T., Pan, G., Romanenkov, V., Schneider, U., Towprayoon, S., Wattenbach, M. and Smith, J.U. (2008): Greenhouse gas mitigation in agriculture. Philosophical Transactions of the Royal Society B 363:789-813.
Woomer, P.L., Palm, C.A., Qureshi, J.N., and Kotto-Same, J. (1998): Carbon sequestration and organic resource management in African Smallholder agriculture. In Lal, R., Kimble, J.M., Follett, R.F., and Stewart, B.A. (eds.), Management of Carbon Sequestration in Soil, CRC Press, Boca Raton, Fl. 153-173.