Nutrient Management Survey Reveals Industry Practices

By Dr. Patty Skinkis, Oregon State University

The NGRA-initiated High-Resolution Vineyard Nutrient Management project, led by Washington State University’s Markus Keller, received second-year SCRI funding this fall. Organized to develop both sensor-based tools to measure in-field grapevine nutrient status and regional nutrition guidelines, the research will help growers to manage vineyard nutrition using precision viticulture.

But first, the team set out to benchmark how the industry is—or isn’t—managing vineyard nutrition today. A survey was conducted in Spring 2021 to give the team an overview of current practices, gauge the appetite for new technologies, and guide future research.

The survey was completed by 322 people, representing 25 states, nearly 176,000 acres and all four grape sectors (juice, raisin, table and wine grapes). The majority of respondents were grape growers (88%), including vineyard owners, managers or viticulturists. The remainder of respondents were consultants (7.5%) and vineyard management companies (4.5%). Their responses may surprise you!

Nutrient Management Plans
The majority of respondents nationwide (88%) did not have nutrient management plans for their vineyards. Maryland had the highest percentage of respondents with nutrient management plans (86%), followed by Idaho (33%) and California (24%). The majority of farm nutrient management plans (71%) were primarily developed for regulatory compliance (e.g., Natural Resource Conservation Service [NRCS] or Soil and Water Conservation Districts [SWCD]). Only 17% indicated that a farming certification required them to have nutrient management plans and even fewer (12.5%) indicated that it was required by their company. For growers with nutrient management plans, 63% developed their own plans, 26% used a crop consultant, and only 11.4% used public resources, such as NRCS, to draft that plan.

Nutrient Testing
The majority of respondents (57%) determined nutrient status using both tissue and soil testing rather than soil or tissue testing alone.

Tissue testing. The majority of respondents (60%) test vine nutrient status annually and 23% test every two to three years. Just under half (47%) only test petioles, and 10% test only leaf blades. Whereas 22% of respondents test both leaf and petiole samples separately (two different tests), 19% of respondents collect composite leaf samples where whole leaves (blade + petiole) are tested.

Tissue test timing was split between bloom and véraison, with 44% of respondents sampling at both bloom and véraison. Most (62%) sample vineyards at a rate of <5 acres per sample. However, 31% of respondents sample 5 to 20 acres per sample. Area represented in a tissue sample was not related to total farm size; growers with larger vineyards did not necessarily sample larger areas.

Soil testing. The majority of respondents test vineyards soils regularly. Most (43%) test soils every two to three years, but 20% test annually and 24% test at intervals greater than three years. The remaining respondents test vineyards only when problems arise (10%) or when required by regulation (2%).

Fertilizer Application
The regular sampling of vine tissues and soil has the potential to help producers understand when and how to fertilize, as 75% of respondents indicated that they apply fertilizers annually. Respondents apply both foliar (66.5%) and soil-applied (74.3%) fertilizers, representing macronutrients (Nitrogen [N], Phosphorous [P], and Potassium [K]) at 61% and micronutrients at 55%. The nutrients of greatest concern for respondents are N, K and Boron (B). As expected, there were differences in macro- and micro-nutrient concerns by state, with NY and TX having greater concern for N than the other states. K was the most concerning nutrient in CA and NY, B was the most concerning nutrient in OR, and N was the most concerning in WA.

Deciding how much fertilizer to apply can be challenging. Only 29% of respondents indicated that they determine their own fertilizer rates. Just over half of respondents (50.6%) rely on recommendations from crop consultants, vineyard management companies or Extension agents. A few (14%) use recommendations from testing labs. The rest (6.4%) use visual cues, observations, experience or routine to guide which fertilizers and rates to use. The majority of respondents (65.3%) apply fertilizers differently across vineyard blocks, whether by soil characteristics, or crop quality or production goals.

Importance of Vineyard Nutrition Management
Although 73% of respondents agreed that nutrient management was very or extremely important to achieve yield or quality targets, the majority indicated that nutrient management costs comprise only 5-10% of their total vineyard management budget. The majority (64%) believed there would be yield losses with improper nutrient management. But most believed it wouldn’t impact the unit price paid for their fruit (68%).

Technology Use
Only a small fraction of the respondents (17%) use technology (most commonly, remote and proximal sensing) to assist in vineyard nutrient management. Why such low adoption? Respondents reported that technologies are either not necessary or too costly, or they don’t know how to use them. This means that nutrient management tools developed for growers need to be easy to use and cost-effective. However, input on new tools should also come from crop advisors, consultants and vineyard management companies who are making most fertilizer and application rate recommendations.

Patty Skinkis is a Professor and Viticulture Extension Specialist at Oregon State University. As a collaborator on the HiRes Vineyard Nutrition project, she organized and analyzed this survey. This article was excerpted from her original summary, “Nutrient Management Survey Helps Research Team Understand Current Industry Practices,” published in October 2021 on the HiRes Vineyard Nutrition project website. Download the original.

See also this related story, “Research team working to update decades-old vineyard nutrition guidelines, improve grape tissue sampling,” published this month by WSU CAHNRS News.