ABSTRACT


Víctor Volke H.1
 
Based on 42 experiments on the response of wheant to nitrogen and phosphorus applied to "trumao" soil in the provinces of Malleco and Cautin, a study was made on the optimal dosis of these mutrients for wheat, and on the degree of association of these optimal dosis and the level present in the soils when dtermined at the assimilable state in the laboratory. The soils under study were trumao Santa Bárbara (slopes) and trumao Victoria, Agua Fría and Vilcún (plains). Nitrogen in the soil was determined with the Keeney and Bremner incubation method, considering nitric and amonium nitrate; the Olsen method, modified by Schenkel, was used for phosphorus determination. Wheat cultivars sown in the present study were Cappelle Desprez (winter), and Chifen and Pumafen (spring).Nitrogen was applied as sodium nitrate (16% N) and phosphorus as treble superphosphate (47% P205 ), both at 5 different treatm nt levels. A polinomial second grade regresion equation was adjusted to treatment vields obtained. Bas d on these equations and the price relationships of fertilizers and the production obtained, optimal dosis for nitrogen and phosphorus were calculated.The following was concluded:
l. Optimal dosis for both winter and spring wheat cultivars were:a) Nitrogen: - For trumaos on slopes, 60-90 Kg/ha.b) Phosphorus:
- For trumaos on slopes, 180-220 Kg/ha (expresed in P205)
- For trumaos on plains, 160-200 Kg/ha.
II. The high level of association observed between the optimal dosis of nitrogen and phosphorus determined as yield response in wheat production, and content of these assimilable nutrients in the soil determined by laboratory analysis, gives good support for determination of an optimal dosis of fertilization through soil analysis.
Keywords:
1Ing. Agr., M. S., Centro Suelos y Riego. Estación Experimental Carillanca, Instituto de Investigaciones Agropecuarias (INIA), Chile. Actualmente en CIMMYT. Londres 40, México, D. F., México.