Conservation Agriculture (CA) aims at increasing soil productivity and profitability of farming while protecting resources against degradation. Three underlying principles characterise CA-cropping systems:
- minimal or no-tillage of soils
- permanent cover of soils with plant residues (Seeds are sown directly into the soil under the residue layer)
- crop rotation
While the combination of these three main characteristics is common to all CA- approaches, there is a great variety of different forms, which have been developed through adapting to different agro-ecological and socio-economic conditions. Smallholder farming in the tropics and subtropics are such adaptations. CA can be applied in both, rain-fed and irrigation agriculture. Effective use of water, and protection of soils from run-off water and erosion, as well as the capacity to raise or maintain higher levels of soil organic carbon (sequestration of carbon) than in conventional tillage cropping systems, makes CA a strategic choice in terms of sustainable land-use, as a mitigation measure for climate change and also for agriculture water management.
Soil degradation and declining yields which are resulting in a lower profitability of farming have been the main drivers for the development of CA. Modern forms of CA first developed in Latin America, mainly in Southern Brazil, where large-scale commercial farmers started experimenting with alternatives to conventional tillage, as soil erosion through wind and rain were difficult to control (1). In Argentina CA spread fast when it became possible to use the herbicide glyphosate (round-up) for weeding in combination with glyphosate-resistant crop varieties. The economic success of CA lead to a strong increase of area farmed with these methods. Data from 2009 (2) report over 100 Mio ha of arable land covered by CA, Latin and North America being the most important adopters, followed by Australia and New Zealand. In Africa, it is mainly in the southern part where modern CA-practices have spread. CA had early forerunners in traditional hand-hoe agriculture as practiced, for example, by the Chagga on fertile soils of the steep slopes of Mt. Meru in Tanzania. Some of their multiple-storey cropping systems are mulched with residues from bananas and weeds and intercropped with cassava, maize or other annual crops. Farmers used to loosen the soil under the mulch layer with the help of a hand hoe to prepare little pockets into which they sowed or planted (3). Today’s smallholder farming has spread in many continents to marginal land with low soil fertility, little rainfall and often sloping land. CA is considered to offer a potential for intensification and sustainability of this type of farming.
FAO (1, 4) defines CA as an “approach to manage agro-ecosystems for improved and sustained productivity, increased profits and food security while preserving and enhancing the resource base and the environment”. Three principals have to be respected at the same time: (a) Minimal mechanical soil disturbance by tillage and through direct seeding. Strip tillage is allowed when the disturbed area is less than 15 cm wide and less than 25% of the cropping area. (b) Permanent cover of the soil with organic material. If there is less than 30% of soil cover at the time of sowing the plot is not considered CA. (c) Diversification of crops in rotation or intercropped with at least three different species. This definition fixes minimum conditions which are of importance mainly in relation to government programmes and rules in industrial agriculture.
In relation to smallholder farming with manual labour of draft animals more extensive principles are often promoted, as through the Zimbabwe Conservation Agriculture Task Force (5): For instance striving for a maximum soil cover with organic material, no burning of residues, efficiency of use of inputs. In this regard, CA is related to other agro-ecological approaches like agroforestry and ecological farming. Timely execution of operations, in particular weeding, fertilisation and sowing are other aspects paid attention to in the Zimbabwe approach.
In the context of CA, there are several synonymous terms in use like minimum-tillage or no-tillage/zero-tillage or direct seeding, which focus more on the fact of minimum soil disturbance. Conservation farming often refers to a technique of using planting pits to collect rainwater and concentrate fertilisers on one spot instead of spreading it evenly over the whole plot.
Because of its agronomic, economic and environmental benefits the Food and Agriculture Organisation of the United Nations (FAO) promotes CA methods as a potential solution to the difficulties met by smallholder agriculture in developing countries (4). The increase of soil organic matter and, going along with this, the improvement of soil structure, water-holding capacity and nutrient dynamics as well as fertiliser efficiency are the main agronomic advantages, which help to make maximum use of local resources. Environmental benefits come together through the reduction of soil erosion through wind and water. Soils are conserved and siltation of valley bottoms and waterways reduced, while aquifers are replenished (6). Cropland not undergoing tillage produces and releases less CO2 than that under conventional tillage-agriculture. At the same time they store higher amounts of carbon and make it a sink for carbon sequestration (4). If CA is practised with diversified crop rotations and no herbicide is used there is an additional benefit of an increased biodiversity of the agro-ecosystem. Another effect of CA is the improvement of farm economy as inputs and time needed for conventional tillage can be saved. This is through the reduction of cost for machinery, fuel etc. and of labour, in particular during the peak seasons. Reduction and more equal distribution of labour is of particular importance for small-scale family farming, where CA is thought to contribute to assuring livelihood. The long-term stability of the farmland can be considered an economic benefit.
Example for smallholder conservation agriculture
The Zimbabwe Conservation Agriculture Task Force (5) can serve as an example of how CA is adapted to specific conditions of smallholder agriculture in dry areas. The main problems for small family farms are insufficient rainfall and labour shortage during the peak season of planting. Due to the lack of draft animals, many farmers have to do the land preparation manually with a hand hoe. The planting basin method as one element of the local CA is considered to offer a solution under these circumstances. It was developed in the late eighties. The underlying principle is similar to the traditional zaï method in Burkina Faso (7). Already in the dry season, after having weeded the field, small planting hollows (15 to 20 cm in diameter and 15 – 20 cm deep) are dug with a hand hoe without digging or ploughing the whole field. In the drier regions some 18,000 planting basins/ha are recommended, in areas with higher rainfall it can be 22,000/ha. Manure is also placed in the holes and is not spread evenly over the entire field. All this makes an important economy in labour. At the same time, the pits capture water and concentrate it at the centre of the holes, where, after the first sufficient/rainfall, seeds (2 – 5 seeds per pit) are placed. Manure can be positioned close to the crop roots and in this way used more efficiently. The field, in particular the planting basins, are then covered with crop-residues to reduce soil erosion and unproductive evaporation of moisture from the soil. Where farmers succeed to produce enough residues to cover the soil surface completely, the growth of weeds can be considerably reduced. The residues will gradually decompose and contribute to building soil organic matter and supplying nutrients. Crop rotations are necessary to reduce risk of crop failures through disease and pests, to help control weeds and, through the integration of leguminous crops, contribute to nitrogen supply in the cropping system. Examples for rotations in the drier areas are millet/groundnuts/cotton, in the more humid parts maize – cotton – soybean. If the amount of crop residues is not sufficient cover crops can be integrated into the rotation. As weed control through tillage is not an option for CA, timely weeding, when plants are still young, is important. The farming calendar starting in the dry season, after harvest in June, could look like this: dry season weeding - mark out of basins - mulch/residue management - dig basins - manure/fertiliser application – weeding - planting – weeding – top dressing – weeding – harvest. One big advantage of the planting basin method for smallholders is the fact that operations like digging the basins, manuring, residue management can be spread out of the dry season and therefore planting be done early on after the first adequate rains.
For both, manual work and for draft animals, special tools and machinery have been developed for crop residue and cover plant management as well as for direct seeding (1, 8).
Extension work in smallholder family farming
As with agroforestry or ecological farming, practical methods of CA have to be well adapted to local ecological site conditions, but also to the economic and social situation and the institutional setting. CA is a knowledge-intensive approach which needs substantial support over a number of years from extension services helping farmers develop skill and motivation through its repeated implementation. With poor soils, for instance, the production of organic matter which can be used for soil cover might not be appropriate and might need substantial input of manure/fertiliser until a sufficient soil fertility has been established. As all advantages for building favourable soil physical conditions come from permanent organic cover of the soil and not from not tilling the soil, crop residue production and management need highest attention (9). Not tilling without cover might lead to soil compaction und result in declining yields. The amount of work for weed control will also be important to smallholders as they do not have the same possibilities as large scale commercial farmers to use herbicides. The advantages of CA over conventional tillage in terms of total labour input might therefore be lost. This, together with the high management standards required, make the first years a crucial period
- FAO (unknown): Conservation Agriculture. In: http://www.fao.org/ag/ca/index.html [Access 2012-12-18]
- Derpsch R. (2009): Global Overview of Conservation Agriculture Adoption. Paper presented to IV World Congress on Conservation Agriculture. New Delhi, India, February 2009. ‘Source: http://www.fao.org/ag/ca/6c.html [Access 25. March 2013].
- Egger K. und B. Gläser (1975) Politische Ökologie der Usambaraberge in Tansania. Bensheim.
- FAO/Corsi S., Friedrich T. et al (2010) Soil Organic Carbon Accumulation and Greenhouse Gas Emission Reductions from Conservation Agriculture: A literature review. In: Integrated Crop Management Vol.16-2012, FAO, Rome
- Conservation Agriculture Task Force for Zimbabwe (2008): Conservation Agriculture Toolbox for Zimbabwe
- Giller K. E., E. Witter et al (2009) Conservation agriculture and smallholder farming in Africa: The heretics’ view. In: Field Crops Research 114 (2009) 23–34
- Roose E., V. Kabore et al (1995) : Le zaï, une technique traditionnelle africaine de réhabilitation des terres dégradées de la région soudano-sahélienne (Burkina Faso). In : Pontanier R. et al : L'homme peut-il refaire ce qu'il a défait ? Paris. 249-265.
- FAO/GIZ/Florentín, M.A. et al. (2011): Green manure/cover crops and crop rotation in Conservation Agriculture on small farms. http://www.fao.org/fileadmin/user_upload/agp/icm12.pdf [accessed 19 April 2013]
- Mrabet R. (2007) Conservation Agriculture in Morocco: A Research Review. In: Stewart B.A. (Eds) Proceedings of the International Workshop on Conservation Agriculture for Sustainable Land Management to Improve the Livelihood of People in Dry Areas, 7-9 May 2007
- Lahmar R. and B. Triomphe (2007): Key Lessons from International Experiences about Conservation Agriculture and Considerations for its Implementation in Dry Areas. In: Stewart B.A. (Eds) Proceedings of the International Workshop on Conservation Agriculture for Sustainable Land Management to Improve the Livelihood of People in Dry Areas 7-9 May 2007
Further reading and external links
- Dumanski, J., Peiretti, R. et al (2006) : The paradigm of conservation tillage. Proc. World Assoc. Soil and Water Conserv., P1: 58-64.
- File:Neubert, S. (2011) Environmental Benefits of Conservation Agriculture.pdf
- Stewart B.A. (Eds) Proceedings of the International Workshop on Conservation Agriculture for Sustainable Land Management to Improve the Livelihood of People in Dry Areas, 7-9 May 2007
For a collection of pictures and diagrams see: http://www.google.com/search?q=conservation+tillage&hl=de&tbm=isch&tbo=u&source=univ&sa=X&ei=voSGUdnJJqWa1AW54oGIDg&sqi=2&ved=0CEUQsAQ&biw=808&bih=573