Mineral nitrogen in agricultural soils and nitrogen losses: relation to soil properties, weather conditions, and farm practices

abonos nitrogenados agricultural soils conduite de la culture crop management crop yield escorrentia leaching lessivage du sol losses manejo del cultivo manejo del suelo mise en valeur du sol nitrogen content nitrogen fertilizers noruega norway perte rendement des cultures rendimiento de cultivos ruissellement runoff soil management sol agricole teneur en azote weather