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78 WINES&VINES April 2016 GRAPEGROWING PRACTICAL WINERY & VINEYARD balances (see photo at top left). The former compresses soil pores, and the latter disar- ranges them due to soil particle dispersion. To alleviate compaction, shatter and loosen the soil with chisels or rippers. To promote soil aggregation, add organic amendments and calcium as gypsum. Cover crop roots can stabilize soil porosity improvements achieved through deep cultivation, organic matter and gypsum, and can further en- hance them. In addition to advancing soil solution flow toward roots, grapegrowers can encourage the extension of vine roots into greater vol- umes of soil and toward the solution therein. Improving soil permeability, as described above, assists in this effort. Supporting spring and post-harvest flushes of root growth are also crucial. The application of fertilizers containing ammonium-nitrogen, organic acids and ample phosphorus can be particularly beneficial in this effort. It is also essential to control soil-borne pests and diseases that damage and diminish root systems. Plant-parasitic nematodes, Phylloxera and Phytophthora Other measures to improve the root zone environment can enhance mineral nutrient efficiency. These include soil amending to ensure a pH between 5.5 and 7.0, which limits many reactions that remove nutrients from the soil solution. Cover crops can increase soil humus and, correspondingly, cation exchange capacity, which buffers the nutrient content of the soil solution (see lower left photo). Such humus additions also stimulate soil microbes, whose products accelerate the weathering of soil minerals and the release of the nutrients they contain into the soil solution. Finally, optimum mineral nutrient use de- pends on a balanced supply of all mineral nutrients. For example, grapevines may suffer nitrogen deficiency even though ample nitro- gen is present in the soil if vines are suffering either boron or manganese deficiency (see above right photo). Mineral nutrient efficiency may be less than optimal if grapegrowers fail to look be- yond fertilizers and how they are applied. Growers will be more consistently successful if they think broadly about mineral nutrients in the context of comprehensive soil and water management. Stan Grant is a consultant working mainly with grapegrowers and vineyards in the northern interior of California (Lodi, Delta and Sierra Foothills) and the eastern San Francisco Bay Area. 2016 marks the 16th anniversary of his consulting business, Progres- sive Viticulture. Previously, Grant was director of farming at Duarte Nursery and viticulturist with Gallo Vineyards. He earned a master of science degree in soil science from the University of California, Davis. For more information, visit progressivevit.com. This article was edited from its April 2015 publication in the Mid-Valley Agricultural Services newsletter. Wet surface soil becomes compacted under vineyard traffic. Cover crop awaits incorporation into vineyard soil. Interveinal chlorosis (yellow leaves with green veins) is a symptom of foliar manganese deficiency. Further Reading Burt, C; K. O'Connor and T. Ruehr. Fertigation. Irrigation Training and Re- search Center, Calif. Poly. State Univ., San Luis Obispo, CA. 1998. Grant, S. "Balanced Soil Fertility Management in Vineyards." Practical Winery & Vineyard. May/June 2002. Grant, S. "Fertilizer Efficiency for Wine Grape Vineyards." Practical Winery & Vineyard. March/April 2006. Marschner, H. Mineral Nutrition of Higher Plants. 2nd Ed. 1995. Miller, R.J., D.E. Rolston, R.S. Rausch- kolb and D.W. Wolfe. "Drip Application of Nitrogen is Efficient." Calif. Agric. 30, 16-18. 1976. The Fertilizer Institute. "What are the 4 R's?" nutrientstewardship.com/what- are-4rs. (Last accessed Sept. 21 2015.) Tisdale, S.L., W.L. Nelson and J.D. Beaton. Soil Fertility and Fertilizers. 4th Ed. 1985. PROGRESSIVE VITICULTURE LLC