[Nutrient balance in ecological plant production - Kvithamar cultivation system fields]

agriculture biologique avena azote azufre biocenose biocenosis biocoenosis brassica napobrassica calcio calcium contenido de materia seca crop yield cultivo migratorio disponibilidad de nutrientes dry matter content farmyard manure fertilidad del suelo fosforo fumier hordeum magnesio magnesium nitrogen noruega norway nutrient availability nutrition des plantes organic agriculture ph phosphore phosphorus plant nutrition plant production potasio potassium rendement des cultures rendimiento de cultivos shifting cultivation soil fertility soufre sulphur