This study evaluated the environmental impacts of conventional tillage (CT) and no-till (NT) wheat systems in northern Tunisia using the INDIGO assessment method. The study surveyed 3 farms practicing both CT and NT. It found that NT had lower energy consumption (24% reduction) and environmental impact from energy use compared to CT. Pesticide use had a negative environmental impact under NT for one farm due to high glyphosate application rates. Nitrogen fertilization practices had similar environmental impacts under both CT and NT on 2 farms but were excessive on the third farm. This was the first study to assess the agro-environmental impacts of farming systems in Tunisia.

1. Tunis 2010
Environmental assessment of conventional and no-till cerealsystem in the North of Tunisia
By H BAHRI, M ANNABI and K LATIRI
Agronomy laboratory, INRAT Ariana 2049, Tunisia
and L BEN BECHER
APAD, Residence la Lune, Le Lac, Tunis, Tunisia
Summary
In Tunisia, cereals occupy nearly 30 % of the total agricultural land and cover 1.5 million
hectares, of which more than 50% are wheat. Cereals are sown every year between October
and December, predominantly in the northern third of the country called "Septentrionale
Tunisia" and farmers’ practices include mechanization and use of inputs (fertilizers,
pesticides) in order to improve productivity but they might represent a risk for the
environment and the different compartments of agro-system (soil, air and water) through
erosion and water pollution.
Since 1998, no-till system was introduced in Tunisia in order to reduce the cost of agricultural
practices and to preserve natural resources. The aim of this study was to compare and contrast
environmental impacts of conventional and no-till systems. In Northern Tunisia, a survey was
conducted among farmers practicing on the same farm both systems. Indigo model (from
INRA-France) was used to evaluate environmental impacts of nitrogen fertilization, pesticides
treatments and energy use.
Keywords: no till, environmental impact, energy consumption
Introduction
In Tunisia, cereals cover nearly 30 % of the total agricultural land and cover 1.5 million
hectares, more than 50% of which are wheat. Cereals are sown every year between October
and December, predominantly in the northern third of the country called "Septentrionale
Tunisia". Farmers’ practices include mechanization and use of chemical inputs (fertilizers,
pesticides) in order to improve productivity but these practices might represent an
environmental risk in the different compartments of agro-system (soil, air and water).
Since 1998, no-till system has been introduced in Tunisia in order to reduce the cost of
conventional practices and to preserve natural resources. Crop residue management
constitutes an important parameter for this system. In fact, soil organic matter is known as soil
fertility key. Recently, environmental functions have been attributed to soil organic matter
such as soil carbon sequestration in order to reduce CO2 emission into the atmosphere.
In order to evaluate environmental impacts of agricultural practices, different methods
exist. The first generation of these evaluation methods has generally focused on only one
environmental problem which is nitrate leaching (Simon & Le Corre, 1992).Since the
eighties, these tools have emerged in large numbers because they responded to obvious

2. needs.. The development of these methods has been accompanied with the awareness of
environmental problems generated by the intensification of agriculture. In the nineties, a new
type of environmental evaluation method was used which took into account more
environmental problems (Van der Werf & Petit, 2002) such as the INDIGO method
developed by INRA-France (Bockstaller & Girardin, 2003).
The aim of this study was to compare the environmental impacts of the conventional and
the no-till systems in Northern Tunisia.
Materials and Methods
Sites
In Northern Tunisia, a survey was conducted in collaboration with APAD (Association pour
une Agriculture Durable) among farmers practicing at the same time conventional till (CT)
and no till (NT) systems. Three farms grew wheat (farm 1, farm 2 and farm 3).
Method
INDIGO model, which was developed by INRA-France, was used to evaluate the
environmental impacts of nitrogen fertilization, pesticide treatments and energy consumption.
INDIGO method is a scoring method. For each agricultural practice a score is attributed: 0
(maximum risk to the environment) and 10 (no environmental risk) with a recommended
value of 7.
Nitrogen fertilization indicator (IN) assesses the impact of this practice on air and groundwater
qualities taking account of NO2 volatilization and NO3 leaching. The pesticide treatment
indicator (Iphy) assesses risks related to groundwater by leaching, to surface water by runoff
and to atmosphere by volatilization.
Energy consumption indicator (IEn) assesses the impact of energy consumption due to
agricultural practices on air quality through emissions of greenhouse gases or pollutants.
Results
The attribution of a score for each farm about pesticide treatments showed that
for farm 3, in CT and in NT, there is no negative impact of used pesticides and Iphy is about 7.
However for farm 1, in CT and NT, the Iphy is lower than 7. These results signify a bad
utilization of applied pesticide doses.
For farm1 and 2, Iphy for NT is lower than for CT, this difference is due to the pulverization of
glyphosate in NT system.
In our case, IN indicator is only related to the risk of nitrate leaching. For farm 1 and 2,
nitrogen fertilization, based on ammonitrate form, did not have a negative impact on
groundwater (IN ≈ 7). However, for farm 3, IN is about 4. This low indicator value is due to
the overestimation of crop nitrogen needed. For all investigated farms, no difference in IN
value was observed between NT and CT, because farmers use the same nitrogen fertilization
program for both systems.
Crop production is an activity which consumes energy directly by tillage operations, pesticide
treatments, harvest…. Besides, it is important to take into account the indirect consumption
related to input fabrication. For CT wheat system, energy consumption related to fertilization
is higher than machine energy consumption which is about 5870 MJ.ha-1, equivalent to 147 L

3. fuel.ha-1. Concerning NT wheat system, machine energy consumption is about 2438 MJ.ha-1,
equivalent to 60 L fuel.ha-1. For total energy consumption, the average is almost 9365 MJ.ha-1
equivalent to 232 L fuel.ha-1 for NT system and is almost 12350 MJ.ha-1, equivalent to 306 L
fuel.ha-1. Using the quantities of energy consumed, the energy indicator (IEn) was calculated
(fig. 1).
Fig. 1. IEn for NT and CT wheat system
IEn is near to 7 for NT system which signifies a good environmental efficiency of energy
consumption. This indicator is lower than 7 for CT system.
Conclusion
This research project using INDIGO method, in order to evaluate environmental impact of NT
practice, have shown that some practices have a negative impact on the environment. In fact,
pesticide treatments have a negative impact in the case of NT due to the input of an important
quantity of glyphoste molecules.
The principal advantage of NT compared to CT has been observed in energy consumption. In
fact, the reduction of energy is about 24 %.
It is the first time that such a study has been undertaken in Tunisia thus assessing the agrienvironmental impacts of farming systems. This work could be expanded to regions
characterized by aridity.
References
Bockstaller, C., et Girardin, P., 2003. How to validate environmental indicators.
Agricultural Systems 15, 83-89.
Simon J.C., et Le Corre L., 1992. Le bilan apparent de l’azote à l’échelle de l’exploitation
agricole : méthodologie, exemples de résultats. Fourrages 129: 79-94.
Van der Werf, H.M.G., et Petit, J., 2002. Evaluation of the environmental impact of
agriculture at the farm level: a comparison and analysis of 12 indicator-based methods.
Agriculture, Ecosystems and Environment 93: 131-145.