Management of nitrogen and phosphorus fertilizers in Sub-Saharan Africa. Proceedings of a symposium held in Lome, Togo, 25-28 March, 1985

abonos fosfatados abonos nitrogenados afrique occidentale cropping systems economia economics economie fertilidad del suelo fixation de l'azote fosfato mineral mineral resources nitrogen fertilizers nitrogen fixation phosphate fertilizers phosphate naturel recursos minerales rock phosphate sistemas de cultivo soil fertility sol tropical suelo tropical trial methods tropical soils west africa