[The effect of nitrogen fertilizers applied in different terms in combination with green manure on corn performance on cherno-podzolic soils of Polesje region of the Ukraine]

abonos verdes ammonium nitrate appropriate technology calidad crop yield engrais vert fertilizantes nitrogenados grain granos green manures nitrate d'ammonium nitrato de amonio nitrogen fertilizers quality rendement des cultures rendimiento de cultivos secale cereale ucrania rss ukrainian ssr zea mays