Sampling for Degrees Brix in Vineyard Plots

Abstract

Degrees Brix of berry samples and cluster populations were studied from 1977 to 1980 in a mature block of Thompson Seedless grapevines at Davis, California, as well as the °Brix of outer berries of a number of varieties. In 1983, berry and cluster sampling were compared in a crop thinning trial in a commercial vineyard of Cabernet Sauvignon near Oakville, California. The purpose of these experiments was to determine estimates of sampling accuracy and an optimum sample size for precision. Berry samples were generally of higher °Brix than cluster samples. Variances experienced with berry and cluster samples agreed well with standard curves relating sample size to expected variance. In the Cabernet Sauvignon trial, two 10-cluster samples gave a calculated precision equal to two 50-berry samples for detecting a significant treatment difference of 1.0° Brix. Cluster sampling is recommended for greater accuracy.