Mixed farming systems as a way towards a more efficient use of nitrogen in European Union agriculture

aves de corral azote cerdo cycle de l'azote engrais organique european union exploitation agricole explotaciones agrarias farming systems farms grazing grazing systems hortalizas legume mixed farming nitrogen nitrogen cycle organic fertilizers ovin ovinos pastoreo plant production porcin poultry sheep sistemas de pastoreo soil sol suelo swine vegetables volaille