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26 WINES&VINES August 2017 Grounded Grapegrowing "H ealthy vines make great wine" is a truism most viticulturists and winemakers can agree on. In the past two decades, we have seen great strides in defining and improving vine health. This includes the pursuit of virus-free propagation materi- als, irrigation scheduling based on vine moisture status, improvements in integrated pest management approaches to disease and pest control, and more discussion between winemakers and grapegrowers about managing fruit and when to pick for optimum quality. Opinions start to vary when we discuss vineyard envi- ronment and soils management. There is a keen interest among many winegrowers to optimize their soil conditions and provide vines with the resources needed to produce top quality and yield. For a long time we discussed "soil quality," which had a focus on the ability of soils to provide the best vine-rooting environment with functions that include having adequate nutrients, water storage and gas exchange, and the ability of roots to penetrate this porous substrate in search of the resources necessary for plant growth. In recent years, the dialogue has changed as we've begun to understand how agricultural land can also provide ecosystem services that are dependent on biological processes and a broader relationship with the environment. In this article, we will ex- plore some of the principles and limita- tions of the concept of soil health. The real secret life of plants One of the last frontiers in u n d e r s t a n d i n g p l a n t growth is the relation- ship vines have with microbes. Like humans, plants basically have a micro-ecosystem made up of very large populations of microbial organisms. Some colonize internal tissues while others live on external surfaces. Combined with the vast diversity of microorganisms in the soil rhizosphere, these plant- and soil-associated microbes comprise the plant microbiome. The microbiome is intricately involved in plant health and serves as a reservoir of additional genes that plants can access when needed. The study of microbiomes is an emerging field that has greatly benefited from bio- technology including genomics and improved methods for measuring plant physiology and metabolites created by both plants and microbes. Based on present knowledge, three sub-microbiomes are recognized. The phyllosphere are leaves and the microbes that dwell on them, which can be quite important to their plant hosts. Leaf-associated bacteria can influence host growth and function in many ways, including the production of growth-promoting nutrients and hormones that help protect hosts against pathogen infec- tion. How this ecosystem works is not well understood. Regardless, there are biofungi- cides in use today that utilize this idea to help prevent disease from occurring by competi- tion for space and also destruction of the pathogen itself. As a region, the microbe population density on leaves is probably rela- tively low compared to other areas of the vine, as microbes often rely on plant exudates as a food source. Vine leaves are not particularly "leaky." The fructosphere con- sists of fruit and the mi- crobes associated with that area. Since early n GLENN McGOURTY Attention Turns from Soil Quality to Soil Health