Long-term field experiments - museum relics or scientific challenge?

abonos npk acide organique alemania allemagne biodiversidad biodiversity carbon carbone carbono centeno chernozem chernozems chimie du sol crop yield engrais npk engrais organique farmyard manure fertilisation fertilizer application field experimentation fumier germany hidrocarburos humus hydrocarbons hydrocarbure inorganic fertilizers land use micro-organisme du sol microorganismos del suelo monocultivo monoculture npk fertilizers nutrientes nutrients organic acids organic fertilizers pedogenese phaeozem phaeozems rendement des cultures rendimiento de cultivos rye secale cereale seigle soil chemistry soil genesis soil microorganisms soil organic matter substance nutritive trial methods utilisation des terres