The Departamento de Investigaciones Agrícolas carried on between the year 1940-1946 a series of field trials on the effect of tue "four elements' (N P K Ca) on wheat; results of these trials are summarized in this article. Besides, results of a series of factorial field trials on the effect of "rates of aplication of lime and phosphorous fertilization" on wheat are presented by the first time.
An attempt at interpreting these results is made considering the modern criteria aboutthe function of liming.
In the trials on "four' elements" it was found out that lime increases yields in the acids soils, south of the Maule river; these increases are not so common as the increases induced by nitrogen or phosphorous. The effect of liming is important in granitic soils and in red clays but it is erratic and generally small in volcanic soils ("trumaos"); among the volcanic soils, that of Victoria was the one in which the response to lime was better.
Trials on "rates of aplication of lime and phosphorous" were located only insoils south of the Maule; they were carried on between the years 1947-1951. Several rates of aplication of lime (500 to 4000 Kg. CaO per Ha.) were tested combined with different amounts of phosphorous fertilization (50 to 300 Kg. P2O5/Ha.).
All the soils tested gave a big response to phosphorous. Same as in the "4 elements" trials, response to lime in "trumaos" was erratic and rather small,and was marked and constant in granitic soils and red clays. Response to lime in all the soils tested tend to decrease when the rate of phosphorous fertilization is increased. When the highest rate of phosphorous is used (300 Kg. P2O5/Ha.) response to lime nearly desappears.
When common rates of phosphorous fertilization are used (50 Kg. P2O5/Ha.) this interaction is small and practically the effect of the combined ap

1 Ingeniero Agronómo. Sección Suelos. Departamento de Investigaciones Agrícolas.