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p r a c t i c a l w i n e r y & v i n e ya r d M a r c H 2 0 1 4 63 g r a p e g r o w i n g seems to play a role in phloem function- ing and is imported into fruit during a period of rapid sugar accumulation, sugar translocation during ripening may be affected by K deficiencies, especially near véraison. 5 In some instances the applica- tion of K fertilizer can lead to higher Brix at harvest. 7 On the other hand, high K levels in fruit can be a concern due to associated high levels of K in must and wines and the associated high must and wine pH. 9 Wines with high K content have been shown to have a high wine pH, which can cause reduction in wine color in red wines via impact on anthocyanin equilib- ria and increased problems with chemi- cal and microbial stability. The high pH of wines observed after vinification of fruit from high K soils or in irrigated vineyards is a concern in many wine regions. PWV References 1. Barber, S.A. 1962 "A diffusion and mass-flow concept of soil nutrient availability." Soil Sci. 93: 39–49. 2. Kuchenbuch, R., N. Claasen and A. Jungk. 1986 "Potassium availability in relation to soil moisture." Plant and Soil. 95: 221–231. 3. Nye, P.H. 1966 "The measurement and mechanism of ion diffusion in soil. I. The relation between self-diffusion and bulk diffusion." J. Soil Sci. 17: 16–23. 4. Iland, P., and B. Coombe. 1988 "Malate, tartrate, potassium, and sodium in flesh and skin of Shiraz grapes during ripening: concentration and compartmentation." Am. J. Enol. & Vitic. 39 (1): 71– 76. 5. Rogiers, S.Y., D.H. Greer, J.M. Hatfield, B.A. Orchard and M. Keller. 2006 "Solute transport in Shiraz berries during development of late- ripening shrinkage." Am. J. Enol. & Vitic. 57 (1): 73–80. 6. Sipiora, M.J. 1994 "The influence of irrigation on the mineral nutrient status of Cabernet Sauvignon grapevines in Somontano with special attention on potassium." In: Proc. VII Journee d'etude des Systemes de Conduite de la Vigne (GESCO), Valladolid, Spain: 308–313. 7. Sipiora, M. 1991. "Soil, vine, and management factors affecting grape- vine potassium status in North Coast vineyards." MSc Thesis. UC Davis. 8. Sipiora, M.J., M.M. Anderson and M.A. Matthews. 2005 "A role of irrigation in managing vine potas- sium status on a clay soil." Proc. Soil Environment and Vine Mineral Nutrition. In: Soil Environment and Vine Mineral Nutrition. P. Christensen and D. Smart (Ed.) Am. Society for Enol. & Vitic. 9. Sipiora, M.J., M.M. Anderson and M.A. Matthews. 2005 "Composition of Vitis vinifera L. cv. Pinot noir fruit and wines from Carneros Appellation in response to potassium fertilization and supplemental irrigation." Proc. Soil Environment and Vine Mineral Nutrition. In Soil Environment and Vine Mineral Nutrition. P. Christensen and D. Smart. (Ed.) Am. Society for Enol. & Vitic. 10. Williams, L.E., and P. J. Biscay. 1991 "Partitioning of dry weight, nitrogen and potassium in Cabernet Sauvignon grapevines from anthesis until harvest." Am. J. Enol. & Vitic. 42 (2): 113–117. Soil K concentra on Soil moisture level K availability High High High to Excessive High Low Adequate Low High Adequate (?) Low Low Low (deficiency most likely) Table V. Influence of soil P or K content and soil moisture on availability of P and K.