Schenkel S., Gotardo1, Baherle V., Pedro2, Floody A., Horacio3 y Gajardo M., Mauricio4.

The nutritive deficiences of 70 soil samples of the Biobío provincef are determined with Lolium perenne x Lolium multiflorum in pot trials.
Phosphorus constitues the criical element in all soils, no matter which its origin is, being a generalized mineral deficiency.
The mean values of the parameters that define the fertility lines permit to establish the following decreasing order for the importance of the nutritive deficiency: phosphorus, potassium, sulfur, micronurients (B, Mo, Zn, Cu, Mn), magnesium and occasionally calcium.
This order is the same observed in the soil samples of the Malleco province, but the order of the deficiency of sulfur and potassium is altered in soil samples of the Ñuble province, where the sulfur deficiency is more important than the potassium deficiency (Araos, 1967).
Phosphorus deficiency is particularly severe in the soils near Santa Barbara area. Sulfur and potassium deficiencies are restricted to a certain soil series or o specific areas in the Biobío province being important the East and Southeast of Mulchen with soils of low potassium reserve. Field experiment with sugar beet relate the response to poassium ferilización in poor soils with the soil management done in the farm (Rojas, 1973 and 1978).
It is urgent the identification of the micronutrient or micronutrients which are lacking, because the damages caused for this deficiency in soils could become more important tha the phosphorus defciency.
The conclusions found in different field experimens with soils in the Biobío province agree with the findiengs of this paper.

1Ingeniero Químico, Casilla 244, Osorno.
2Ing. Agr., Líder Nacional Proyecto Fertilidad de Suelo, Estación Experimental La Platina, Instituto de Investigaciones Agropecuarias (INIA), Casilla 5427, Santiago, Chile.
3Laboratorista Químico, Universidad de Concepción, Casilla 537, Chillán, Chile.
4Ayudante Laboratorio, Proyecto Fertilidad de Suelo, Estación Experimental Carillanca, Instituto de Investigaciones Agropecuarias (INIA), Casilla 58-D, Temuco, Chile.