Spatial Variation in Soil Chemical and Physical Properties and Precision Agriculture in Two Carneros Pinot Noir Vineyards.

In 2003 a limited amount of funding was obtained to initiate a research program that would be used to establish a Precision Viticulture Research Group at UCDavis. The goals outlined for our first year of support were to document the existence of spatial variation in fruit ripening and other indicators of vine performance, and to ascertain whether such variation correlated with soil heterogeneity. Spatial non-uniformity in winegrape vineyards is recognized, and its influence on production practices is the subject of much discussion. Nonetheless, the extent of such variation, its documentation and quantitative influence on vineyard production, and information or analysis linking such variation to specific soil properties is scarce. The extreme spatial variability that exists in soils is the major reason for the existence of the science of Precision Agriculture. How the principles of Precision Agriculture will be applied to viticulture practices, and what resources and vine parameters will be important to assess, will form the basis of our work.

We made substantial progress in 2003 using the support we received. Sampling grids were established in both of the targeted vineyard sites. In one such site, over one thousand observations concerning ripening uniformity, fruit quality, vine size, yields and pruning weights were acquired. The data revealed large differences in grape ripening (brix, range = 17.3-24.2, on August 12, 2003). Brix did not vary randomly from vine to vine, rather, it varied in a discernable pattern. Pruning weights appeared to correlate with ripening. Higher Brix readings were observed in the same vineyard locations where higher pruning weights were found. At the second vineyard site, parallel information was acquired with the exception of the fruit quality and yield information, and our efforts there were limited by funding restrictions and the fact that sampling protocols had to be established. In the coming year we will continue these investigations focusing on soils sampling and mapping, along with the collection of more fruit and vine data.