COMPARATIVE STUDY OF THREE METHODS OF NUTRITIONAL DIAGNOSIS FOR GRAPEVINES
Abstract
Nutritional status of Cabernet Sauvignon vineyards in the Serra Gaúcha region was evaluated, according to the methods developed in Califomia, Michigan and South Africa. The Californian method, using leaf petiole sampled at flowering, identified no nutritional troubles for P, K, Mg, Mn and Zn, but B was deficient in 83.3% of the vineyards. The Michigan method, using leaf petiole sampled during "véraison", identified no nutritional troubles in the vineyards for B, Fe and Mn. For N, 58.3% were below normal nutritional class, and the others were normal; for P 25.0% were normal and 41.7% above normal; K was excessive in 58.3% and above normal in 25.0%; Ca and Mg were normal or in excess for all vineyards; Zn above normal in 75.0%. For the South African method P and B were normal in all vineyards; N in 83.3%; K, Ca, Mg, and Mn were above normal in 91.7% of the vineyards, and Zn in 75.0%. Differences found among methods were probably dueto the phoenological state when samples were taken and tissue analysed.
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