IWRA Proceedings

AbstractThe impacts of direct seeding on soil and environment protection in the Mediterranean climate For oral presentation M.R. Khaledian1,2, J.C. Mailhol1, P. Ruelle1, F. Forest3, D. Rollin1 1) UMR G-EAU Cemagref-Cirad-Engref-IRD, BP 5095, 34196 Montpellier Cedex 05 France 2) Guilan University of Iran Tel: +33 467 166 412, fax: +33 467 166 440 email:mohammad.khaledian@cemagref.fr 3) Direct seeding research unit, Cirad, Montpellier, France A key principle of direct seeding into mulch (DSM) system is the retention of crop residues on the soil surface to preserve soil water for crop growth. In response to the negative impact of soil degradation processes under conventional cropping systems that are based on soil tillage, DSM system without tillage practices and with protective cover of crop residue are being developed in many parts of the world. Apart from the positive effect on soil conservation and sustained land productivity, another major impact of DSM is decreasing labour costs, generally leading to higher income and a better standard of living for the farmers. Water is often a major limiting factor for crop production. Soil water availability is directly related to environmental factors i.e. precipitation, evapotranspiration, soil type and topography, but may be influenced by agronomic practices, including irrigation, fallowing and sowing time, or via specific water conservation practices, such as terracing and mulching. However DSM is a successful system especially in the south of America, but the impacts of system in the Mediterranean climate especially in the south of France is less well known; so that this study has been carried out within the scope of an European project. Durum wheat was sown for two years on Lavalette experimental site in Montpellier (43° 40’N, 3° 50’E, altitude 30m) in the south of France. There were two main treatments: DSM and conventional tillage (CT). There were different irrigation and nitrogen rates. Crop production, water and nitrogen balance, soil bulk density, plant density, infiltration rate, soil temperature and soil water content in different layers, soil preparation time and diesel oil consumption, root development, soil carbon, soil nitrogen and soil organic matter were assessed and compared in these two systems. The results show that the crop production is higher in CT system, where nitrogen losses and water use efficiency are higher too. In environmental protection view, DSM system has more advantages such as increasing soil water content, soil carbon, soil nitrogen and organic matters which may have a direct and positive impact on the soil quality. DSM decreases soil preparation time, diesel oil consumption and nitrogen losses, which mean that DSM could mitigate Co2 emission by decreasing fossil fuels consumption. The results show that the presence of mulch can limit soil evaporation and stores extra soil water content, which is suitable for crop and mineralization during dry periods. DSM decreases soil temperature and moderates its fluctuation in the top soil layer which the first effect can increase the necessary time for plant emergence for winter crops. All in all, DSM can be considered as a reliable alternative crop system in the Mediterranean context.