Biological evaluation of potassium and magnesium deficiencies in fruit trees

Rafael Ruiz S.1 y Edgardo Moraga S.1

Deficiencies of K observed in table grapes and of Mg in apple trees, were biologically evaluated through pot experiments, using soil from different layers of the profile. By comparisons between dry matter yield and nutrient absorption, with or without the theoretically deficient nutrient, a relationship between the deficiency present in the trees and the growth of forages was established. The clover used to evaluate the K problem, clearly showed the deficiency and confirmed, under biological basis, that the chemical fixation of K observed previously in the same soil, signifies a lower availability of K to the plant. Similar experiments where conducted with ryegrass, to evaluate the Mg deficiency. Results indicated a nulle effect of Mg agregation to the pots, in terms of dry matter yields. Magnesium absorption was, however, increased by higher levels of mineral N and organic matter present in the soil profile. This effect was grater than the agregation of Mg itself. A discussion of the meaning of these results in terms of Mg deficiency in the trees, is presented.

1 Estación Experimental La Platina (INIA), Casilla 439, Correo 3, Santiago, Chile.