ChileanJAR

At he Cauquenes Experimental Station (INIA). a field experiment was conducted from 1972 to 1981, using different sources and levels of N/ha, imposed to unirrigated Pedro Jiménez grapevines (Vitis vinifera L.). The general methods were described in a previous paper (Lavín y Valenzuela, 1986). Petioles were used to estimare the treatments'effects on levels of N, P, K, Ca and Mg. Doses of N used had no effect on the N content in the petioles. Concentrations of 0.75% N at full bloom, and 0.5% at fruit maturity, were considered adequate references for the vineyards of the area. The limited need to include P in the fertilizing program was confirmed; 0.1% was considered a good reference value at full bloom. At fruit maturity, P concentration can be as low as 0.06%. A significant interaction between sources and doses of N was found for K; concentrations of the latter, at full bloom and fruit maturity, were generally high, and in excess of 3% at full bloom. Calcium concentrations were not affected and considered adequate. Also, meassured Mg concentrations were adequate and generally aboye 0.3% at full bloom. Chilean nitrate generally diminished Mg concentrations in petioles.