[Efficient rates of nitrogenous fertilizers applied to natural grass stand of Arctagrostis wild cereal of the Polar zone]

application rates clima polar climat polaire composition crop yield dose d'application fertilizantes nitrogenados gramineas graminee grasses natural pastures nitrogen fertilizers pastizal natural plantas silvestres plante sauvage polar climate prairie naturelle rendement des cultures rendimiento de cultivos urss ussr wild plants