Santosh Kalauni, Roger Paul Schreiner,* and Patricia A. Skinkis
*United States Department of Agriculture-ARS-HCRL, 3420 NW Orchard Ave, Corvallis, OR, 97330 (paul.schreiner@usda.gov)

Mineral nutrients play a crucial role in ensuring optimal vine growth and high-quality fruit production. This study investigates the effects of nitrogen (N), potassium (K), and magnesium (Mg) fertilization on vine nutrient status, productivity, and fruit composition in western Oregon vineyards over three years (2021 to 2023). Three trials were conducted: one focused on N in Chardonnay, while the other two addressed deficiencies of K and Mg in separate Pinot noir vineyards. Each trial had treatments replicated four times using a randomized block design. The N trial involved three rates of soil-applied N (no N, 20 lb N/acre, and 40 lb N/acre), while the K trial included both soil (no K, 200 lb K/acre, and 400 lb K/acre) and foliar fertilizer (3.3 lb K/acre) treatments. The Mg trial focused solely on foliar applications (no Mg, 3 lb Mg/acre, and 6 lb Mg/acre). Key findings revealed minimal effect of N on growth and fruit metrics, yet it positively influenced vine N status, with effects varying across different tissue types and over time. Additionally, juice yeast assimilable nitrogen levels increased as the N application rate increased. Notably, soil-based K application had more visible effects than foliar application or no K on vine growth; vine K status across leaf blade, petiole, and dormant stem; and juice pH by the end of the third year. The Mg trial had limited effects on vine growth and productivity, although leaf blade Mg increased with greater Mg application rates. Petioles did not respond significantly across the years. However, foliar Mg application reduced the severity of symptomatic leaves, particularly at high and medium application rates. These findings contribute to our understanding of nutrient management in western OR vineyards and are being used to establish critical nutrient levels tailored to specific grape varieties in the region and nationally as part of the High Resolution Vineyard Nutrition Project.

Funding Support: National Institute of Food and Agriculture-Specialty Crop Research Initiative Coordinated Agricultural Projects (CAP) grant project award number: 2020-51181-32159