Domingo Godoy H.1, Carlos Muñoz S.2 y Bruno Razeto M.3

In order to determine the critical concentration of potassium on Fortuna peach trees, an essay was conducted under greenhouse conditions, working with nutrient solutions in sand culture, using eight potassium levels: 0- 10 - 25 . 50 - 75 - 100 - 200 - 400 ppm.
The experimental design consisted of randomised blocks, with three replications per treatment.
Shoot lenght and plant diameter was measured weekly, and leaf size was determined every 15 days.
Dry weight of the complete plant and of parts of it were determined at the end of the essay. Leaf and root samples were taken to determine its content of nitrogen, phosphorus, potassium, calcium and magnesium.
Potassium presented a clear effect on growth, but each part of the plant responded in different from to this element: roots presented the least response and the shoot lenght, the greatest.
At concentrations of 0 and 10 ppm of potassium in the nutrient solution, deficiency visual symptoms on the leaf were observed. This concentrations corresponded to contents of 0.37 and 0.58% of potassium in the leaf and 0.14 and 0.17% in the roots.
A range varying from 1.33 to 1.96% of potassium in the leaves, and from 0.31 to 0.37% in the roots is proposed as the critial level. Other nutritional aspects of this element were also studied.

1Ing. Agr., Proyecto Fruticultura, Estación Experimental La Platina, Instituto de Investigaciones Agropecuarias, Casilla 5427, Santiago, Chile. Profesor Propagación de Plantas, Escuela de Agronomía, Universidad Católica de Valparaíso.
2Ing. Agr., CORFO, Iquique.
3Ing. Agr., M. S., Profesor Fruticultura, Facultad de Agronomía, Universidad de Chile.