1. Nitrate concentration in soils and subsoils as affected by farming practices in intensive agricultural areas N. Beaudoin 1, B. Mary 1, P. Durand 2, J.M. Machet 1 & B. Nicolardot 1 1 INRA - Unité d’agronomie de Laon-Reims-Mons, France 2 INRA - UMR S.A.S, Rennes, France 14 th N WORKSHOP N management in Agrosystems in Relation to the Water Framework Directive 24-26 October 2005, Maastricht, The Netherlands

2. Effect on the destruction on soil net N mineralisation and the potential risk of N leaching N dynamics in the RZ – Agricultural Practices 0 100 200 300 400 500 600 Feb.-97Aug.-97Feb.-98Aug.-98Feb.-99 kg N mineralised ha -1 From Vertes et al., 2002

3. Effect of the presence of catch crop on the amounts of N leached N dynamics in the RZ – Agricultural Practices Continuous barley, 5 years study, D=635 mm, Denmark Hansen & Djurhuus, 1996 Sugar beet-Wheat-pea, 10 years study, D=125 mm, France Mary et al., 2002 kg N ha -1 0 20 40 60 80 No CCCC kg N ha -1 0 10 20 30 40 No CCCC

4. Effect of increased fertilisation on N balance (Inputs – Exportations) N dynamics in the RZ – N leaching & N balance -40 0 40 80 120 160 080160240 N rate (kg N ha -1 ) N balance (kg N ha -1 ) Ropsley 1977-1992 UK 1941-1992 G + I + L From Davies & Sylvester-Bradley, 1995 G = gaseous losses, I = soil N immobilization, L= leaching losses

5. Relationships between N balance and nitrate losses N dynamics in the RZ – N leaching & N balance 0 10 20 30 40 50 60 N0.65N N + CC 0.65N + CC N balance kg N ha -1 0 20 40 60 80 100 120 N0.65N N + CC 0.65N + CC Nitrate concentration mg NO 3 - L -1 Mary et al., 2002 Mineral fertilisation and catch crops -40 0 40 80 120 Min N + rotation Min N + maize Slurry + rotation Slurry + maize kg N ha -1 N balance 0 10 20 30 40 50 60 70 Min N + rotation Min N + maize Slurry + rotation Slurry + maize Nitrate concentration mg NO 3 - L -1 Van Dijk et al., 2003 Organic fertilisation and rotation

6. Explicitation of N balance with N losses and N storage in soil organic matter N dynamics in the RZ – N leaching & N balance 0 50 100 150 200 250 300 Inputs - crop exportation Losses kg N ha -1 y -1 N immobilization Volatilization Denitrification Leaching From Wolf et al., 2005 Source: Institut de l’élevage, Paris