[Increase in the productivity of corn through a rational use of fertilization]

abonos fosfatados abonos potasicos alluvial soils analyse statistique cation cationes cations engrais potassique essai fertilisation fertilizer application ion exchange capacity phosphate fertilizers plant response portugal potash fertilizers productividad productivity pruebas respuesta de la planta sol alluvial statistical analysis suelo aluvial trials zea mays