Introduction
Definition of tillage
Tillage is defined as the act of preparing land for the raising of crops. Tilling has been used for ages almost everywhere in the world, thus, several tillage systems have been developed. Three tillage systems can be distinguished: intensive tillage where less than 15% of the crop residue remains on the soil, reduced tillage where the proportion of crop residues remaining is between 15 and 30 % and conservation tillage (more than 30% of crop residue).
Environmental effects of tillage
Among the positive effects of tillage are the destruction of weeds and soil mixing which helps to raise soil quality. It also dries the soil before seeding. However, tillage is also associated with negative effects such as soil erosion, higher rate of fertiliser use, a decrease in the water infiltration rate of the soil, and most crucially in the debate on the impact of agriculture on climate change, tillage also contributes to the loss of many soil nutrients such as nitrogen and carbon by releasing them from the soil into the atmosphere.
Why conservation tillage ?
In the 1940s, several US researchers including Edward Faulkner, Klingman and L.A. Porter thought about another way of growing crops. They called it zero tillage (or no-till farming) and the aim was not to disturb the soil, which would limit soil erosion and increase the amount of water, organic matter and nutrients such as nitrogen and carbon retained in the soil.
The main argument in favour of the zero tillage method is the fact that it increases the rate of carbon input into agricultural soils and it decreases the rate of carbon loss, according to the ecologists. Studies show that the zero tillage method is a practice capable of offsetting greenhouse gases emissions (i.e. mainly CO2, CH4 and N2O which are the most powerful greenhouse gases) by stocking carbon and nitrogen in soils.
On a global scale, it has been estimated that the agricultural sector could potentially reduce radiative forcing of greenhouse gases by a significant amount (1.15-3.3 giga tons of carbon). The zero tillage method has been promoted as an agricultural practice which is said to be a “win-win” situation by enhancing agricultural sustainability by mitigating greenhouse gases emissions on one hand and extending soil productivity on the other hand.
Conservation tillage seems to be an exciting potential solution to minimise the agriculture industry’s adverse impact on climate change, nonetheless it has its opponents and cannot be seen as a panacea. We would propose to study this topic in greater detail in order to better understand the controversy surrounding it.
Key actors
Intergovernmental bodies
The Intergovernmental Panel on Climate Change (IPCC) is the scientific arm of the UNFCCC. The two major groupings within the panel are the Umbrella Group, mainly comprising of the USA, Canada, New Zealand, Australia and Japan; and the EU, backed by many developing countries. The two groups mainly disagree on the extent to which practices such as conservation tillage can be used to offset carbon emissions from industrial production. The former favours the implementation of more flexible mechanisms in calculating carbon emissions targets.
Governments
Policy and institutional aspects have been shown to be an important factor in the adoption of conservation tillage techniques by farmers.
Researchers
Researchers produce the findings at the heart of the controversy, attempting to determine the quantifiable effects of conservation tillage on carbon emissions, the agronomic sustainability of conservation tillage, as well as the identification of factors crucial to the successful adoption of conservation tillage.
Farmers
Farmers choose particular tillage systems to address soil type, crop grown, machinery available, and local practice. Although these systems were originally developed to address water quality, soil erosion, and agricultural sustainability problems, they also lead to changes in soil carbon concentration. Farmers also vary in their scale of production, and farmers with a larger scale of production may be more capable of taking on the socio-economic risk of tillage practices uncommon with local custom without institutional support.
Technology suppliers
Corporate lobbies with a vested interest in the debate include producers of machinery adapted to a particular kind of tillage, and include suppliers of chemical and biological agents such as herbicides and certain variants of crops that are adapted to conservation tillage techniques.
Native biological agents
Key issues
Carbon sequestration may be aided by biological agents such as undisturbed earthworm communities within the soil, as well as bacteria and fungi, which may be adversely affected with the introduction of herbicides and pesticides.
Conservation tillage is confronted to a lot of issues implying very different actors. Our goal will be to explain in an understandable way all those issues as well as the interests and incentives of each actor.
First of all, the scientific proofs about the environmental benefit of conservation tillage are questionable. Is conservation-tillage really effective in order to reduce CO2 emissions ? Can it be applied to all kinds of lands around the world ? To all kinds of crops ? How do we measure the amount of CO2 stocked in non-tilled soil ? Which criteria do we use to measure the CO2 absorption-potential of the soil ?
The question to use or not to use conservation-tillage implies economical issues which can affect not only the consumers and the producers, but also corporations and the governments. Are farmers ready to change their work habits and give away their equipment ? Does it pay out ? Does conservation-tillage imply a rise of crop prices? What are the incentives of the governments ? Should they rather protect the environment or agricultural machinery manufacturers ?
Conservation tillage is characterized, as a CO2 reduction technique, by its reversibility. This means that unless its continued use can be guaranteed, all benefits resulting from it might be lost by a reversion to former methods. The issue of freedom is thus introduced: must governments issue binding laws to force the use of non-till methods? How can they enforce them? Don’t farmers have the right to go back to former techniques if the outcome is not as good as expected?
Ethics also play a role in this controversy. Do we need to use GMOs which are, like Monsanto indicates, more suitable to the use of conservation-tillage ? Or should we apply the precautionary principle and take into account a potential reduction of the crop harvest ? Which impact would this eventual reduction have on global under-nutrition ? Should developing countries have the right to continue the use of traditional tillage methods ?
Finally, conservation-tillage without GMO’s would possibly imply the use of chemical pesticides in order to conserve the quality of the crops and get rid of parasites and weeds. Would the environmental final result of those combined uses be positive ?
Sutdent group members
Here are the members of students group working on this controversy :
- Andrea Chen is our investigator in charge of the fieldwork.
- Sylvain Huchet is our coordinator, responsible for the group management.
- Yannick Gregor is our network analysis in charge of tracing and analysing the networks related to the controversy.
- Shuying Shao is our text-miner and knowledge engineer, responsible for the quantitative analyses of the texts related to the controversy.
- Valentin Bouvignies is our designer in charge of the information and the web design.
