The creation of a linear program, paying particular attention to nitrates assessment as well as to nitrates leaching, according to type of soil, pluviometry, croping system and agricultural practices (first of all : organic manure management). The cost appears to be very high and rises sharply as the nitrates level reaches 10 mg/l. The model shows great sensitivity and allows for the calculation of cost per mg. It also shows the advantages of establishing croping systems and farming practices which release few effluents. Bearing in mind current knowledge and potential developments (compost, better nutrition for cows, technical itinerairies for clean or specified crops - rather than use the term organic - with a higher added value...), it seems possible to maintain and develop a highly efficient localised farming system able to control its effluents.
