Field testing of grape maturity

Since harvesting grapes at the proper stage of maturity is essential to quality—whether the grapes are intended for winery, table, or raisin use—an accurate means of estimating maturity in the field is necessary. Experiments were designed to measure the reliability of three field sampling methods—individual berry, cluster, and whole vine—in order to provide a more rational basis for grower practice. The varieties tested were Semillion and Carignane in regions II, IV, and V, Thompson Seedless in regions IV and V, and Flame Tokay in region IV. The degree Balling, Abbé refractometer reading, per cent reducing sugar, per cent total acidity, and pH were determined on all samples. According to these analyses, the three methods compare very favorably. It is suggested, however; that berry sampling, since it is the simplest and most rapid of the three methods, may be the most practical.