Survey of soil nutritive deficiencies using pot experiments. XXIV Behavior of Mg in a fertilization formula NPKCaMgS

Gotardo Schenkel S.1 Pedro Baherle V.2 y Mauricio Gajardo M.3

In a pot experiment, 458. soils from the area between Arauco and Magallanes were seeded with LoIium perenne x L. multiflorum and fertilized with NPKCaMgS, using the commercial fertilizers Triple Superfosphate and Potassium Sulphate plus pure ammonium nitrate and magnesium carbonate.
It was detected that Mgforms part of a multiple deficiency, togetherwith micronutrients. Four groups of soils were stablished:
a. Soils deficient in Mg and micronutrients, with a poor response to NPKCaMgSand NPKCaS (39.43 per cent).
b. Soils with no deficiency in Mg and micronutrients, and with good response to NPKCaMgS and NPKCaS (26.87 per cent).
c. Soils with no deficiency in micronutrienis and only occasionally deficient in Mg, with a poor response to NPKCaMgS and NPKCaS (though a little better to this ast one) (18.50 per cent). This group has some soils with an excess of micronutrients, in which the complete fertilization fórmula gives Iower yields than the formula with no micronutrients.
d. Solis deficient in micronutrients and, in some cases, also in Mg, with a good response to NP KCaMgS and NP KCaS (15.20 per cent).
The responses observed, are explained by the presence of micronutrients in the commercial fertilizers and supposing Ihe existence of two, and in some cases three, problematic micronutrients.

1 Facultad de Ciencias Agropecuarias y Forestales, U. de Concepción, Casilla 537, Chillán, Chile.
2 Estación Experimental La Platina (INIA), Casilla 5427, Santiago, Chile.
3 Estación Experimental Carillanca (lNlA), Casilla 58-D, Temuco, Chile.