Field tríaIs on comparisón of differents phosphorus fertilizers in several farms of the Chilean Ministery of Agriculture point out to the following facts.
Using the same amount of P205, superphosphate, chilean thermic phosphates ("Melón" and "Pelícano") and North African phosphorite ("Hyperphosphate") seem to have same effect; the results on phosphorite are limited so the statement can not be conclusive. Red guano and bone-flower have abont the same immediate effect and this effects is about half the effect of the phosphates named before.
The yield of the pasture sward that follows wheat in the rotation indicates that the effect of the different sources of phosphorous used in the trials tend to equilize after the first year following the aplication.
The effect of application of the organic fertilizers, (bone meal and red guano) at seeding time was practically the same as the application of these fertilizers a month earlier.

1 Ingeniero Agronómo, Depto. Investigaciones Agrícolas, Sección Suelos