Ryegrass and white clover undersown in small grains at three nitrogen levels and four tillage treatments : after-effects on grain yields and soil structure

abonos nitrogenados cover plants crop yield estructura del suelo fertilisation fertilizer application labranza lolium multiflorum nitrogen fertilizers noruega norway plantas de cobertura plante de couverture rendement des cultures rendimiento de cultivos soil structure structure du sol tillage travail du sol trifolium repens