Nitrogen leaching from organic agriculture and conventional crop rotations (France)

A great challenge to science is to elucidate how agriculture can feed the increasing world population without damaging the environment, while preserving other resources such as freshwater. In the Seine basin, characterised by intensive agriculture, most of surface and underground water is contaminated by nitrate. Conventional agriculture has regularly increased the use of industrial fertilisers since the WWII, leading to high nitrogen leaching, as shown by lysimeters or suction cup measurements. Such measurements are very scarce for other agricultural systems such as organic farming (Hansen et al. 2000; Haas et al. 2002; Mondelaers et al. 2009). The goal of our study is to investigate nitrogen leaching from organic agriculture, taking into account complete organic rotations (6-9 years). We hypothesize that leaching for organic farming is less than for conventional farming, although factors such as different practices, types of soil and age of conversion need to be taken into consideration. This work should have an impact on nitrogen sufficiency and management of organic practices

Curative vs. preventive management of nitrogen transfers in rural areas: Lessons from the case of the Orgeval watershed (Seine River basin, France)

The Orgeval watershed (104 km(2)) is a long-term experimental observatory and research site, representative of rural areas with intensive cereal farming of the temperate world. Since the past few years, we have been carrying out several studies on nitrate source, transformation and transfer of both surface and groundwaters in relation with land use and agriculture practices in order to assess nitrate (NO3-) leaching, contamination of aquifers, denitrification processes and associated nitrous oxide (N2O) emissions. A synthesis of these studies is presented to establish a quantitative diagnosis of nitrate contamination and N2O emissions at the watershed scale. Taking this watershed as a practical example, we compare curative management measures, such as pond introduction, and preventive measures, namely conversion to organic farming practices, using model simulations. It is concluded that only preventive measures are able to reduce the NO3- contamination level without further increasing N2O emissions, a result providing new insights for future management bringing together water-agro-ecosystems. (C) 2014 The Authors. Published by Elsevier Ltd

Composantes hydrologiques des émissions terrestres du gaz à effet de serre N2O

Etude réalisée pour le compte de l’ADEME dans le cadre de la convention 1660C0003. Rapport intermédiaire[Departement_IRSTEA]GMA [TR1_IRSTEA]11 - VERSEAU / TRANSFEA