Tunis 2010

Environmental assessment of conventional and no-till cerealsystem in the North of Tunisia
By H BAHRI, M ANNABI...
needs.. The development of these methods has been accompanied with the awareness of
environmental problems generated by th...
fuel.ha-1. Concerning NT wheat system, machine energy consumption is about 2438 MJ.ha-1,
equivalent to 60 L fuel.ha-1. For...
Environmental assessment of conventional and no till cereal system
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Environmental assessment of conventional and no till cereal system

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Environmental assessment of conventional and no till cereal system 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

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Environmental assessment of conventional and no till cereal system

  1. 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. 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. 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.

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