Diagnostic tools for grassland fertilization management

Permanent grasslands occupy a very important place in the agricultural landscape. Compared to annual crops, they constitute particular agro-systems that are characterized by the complexity and originality of their mineral element cycle. The work presented is based on data collected in three systems, in the central Pyrenees (Ercé), in the Massif-Central (Gramond), in France and in the southern Carpathians (Dealu Sasului), in Romania. The questions we wish to answer are the following: what is the dose of phosphate fertilizer that is necessary to be at the optimum and to valorize the nitrogen brought by fertilizers and the one released by the mineralization of the organic nitrogen of the soil? 2-what is the evolution of the indicators that allow to make a diagnosis on the level of the availability of P (nutrition indexes, soil analysis...) in relation to the practices? 3-at the end of how long will we see an answer to the impasses of phosphorus and nitrogen. 4-What are the changes in botanical composition associated with the practices?