ABSTRACT.


Gotardo Schenkel S.1, Pedro Baherle V.2, Horacio Floody A.3, Mauricio Gajardo M.4
 

The behaviour of three fertilizaton treatments, N, NP and NPKS ws studied in pot experiments with 59 soil samples from the continental part of the Magallanes province. Results are interpreted by the fertility diagram, using ryegrass.
The response to N alone was very poor, even in those soils with a better phosphorus availabiltity. the only exception was sample 8982, from Riesco island, which showed less deficiencies of all the nutrients.
The yield indexes obtained with NP triplicated those with N alone. this is explained since NP conrrects the phosphorus deficincy, which is the principal one. Fertility is no further increased as a consequence of the serious sulfur and potassium deficiencies.
The soil fertility is increased with NPKS to levels close to the potential fertility. The smallest eficiency is observed in soils that show micronutrient or magnesium deficiencies. The prediction of the N, NP and NPKS treatment effect can be made from their fertility diagram. The position coefficients defined by the N production line are always smaller than the corresponding A coefficients from the fertility line corresponding to the main defficient nutrient. The opposite generally occurs with the NP and NPKS production lines, when the phosphorus or (phosphorus + potassium + sulfur) deficiencies are respectively corrected.
The validity of these results is confirmed with the results of some previous field experiments.

Keywords:
1Ing. Químico, Proyecto Fertilidad de Suelo, Estación Experimental Carillanca, Instituto de Investigaciones Agropecuarias (INIA), casilla 58-D, Temuco, Chile.
2Ing. Agr., Proyecto Fertilidad de Suelo, Estación Experimental Carillanca, INIA.
3Laboratorista Químico, Proyecto Fertilidad de Suelo, Estación Experimental Carillanca, INIA.
4Ayudante de Laboratorio, Proyecto Fertilidad de Suelo, Estación Experimental Carillanca, INIA.