A serie of pot fertilizer trials in wheat, barley and clover on samples taken from 10 Bío-Bío soil series is described. In spite of the big differences among series tested, a big response to P fertilization was common to all of them. Responses to N, K and Ca are unreliable because the used amounts of nutrients were too big and possibly toxic to plants.
It is suggested that the technique employed can be used as a good biological method for determining nutrients deficiences in soils, provided that some modifications will be considered.

1 Ingeniero Agronómo, Departamento de Investigaciones Agrícolas, Ministerio de Agricultura