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When it comes to vineyard nutrition, knowing your shit is the best way to maximise the efficacy of your nutrition management efforts and minimise potential negative impacts on the world around, and below, your vineyard. Spring is right around the corner in the Southern Hemisphere, harvest is looming for those in the Northern Hemisphere, and for both there may be some “major” fertilizer applications in the near future. Whether considering plans for the growing seasons, or a post-harvest pre-leaf fall top-up, keep the following in mind to make the most of your money while doing right by your vineyard and the environment.
Have a plan:
The best way to waste money is to make assumptions and apply “feel good” fertilizers. To be clear, we’re not against fertilizer use. Harvesting grapes removes nutrition every year, and the higher the yield the higher the removal rate, but simply assuming you need to give back what you take based on harvested tonnage is too basic. Testing plant tissue and/or soils is the best way to create a plan that targets the nutritional requirements of your site.
There is debate among growers whether it is better to test vines at flowering versus veraison, or soils in spring versus fall, but regardless of the timing, it is important you remain consistent so that trends over time can be seen.
What To Test? | When To Test? | Notes |
|---|---|---|
Petioles | Flowering* | Wash samples or pay to have them washed |
Leaf Blades | Veraison* | Wash samples or pay to have them washed |
Soil | Spring or Fall | In vineyards that graze sheep intermittently, keep this in mind when picking when to sample. Also should not be sampled at time points too close to fertilizer applications. |
*note: petioles and leaf blades can be taken at both of these time points - these just represent industry standard/basic practice.
Vine tissue tests are going to tell you if your vine is shy of any nutrients (if you can’t already see it). While what the vine “has” is important, we must also think about WHY it has what it has, and so a critical part of that story comes from soil, rootstock (e.g. S04 & 44-53 have poor Mg uptake), and fertilizer applications.
Don’t Treat Your Soils Like Dirt:
If you don’t already know, we’re pretty passionate about soils at Thoughtful Viticulture. Understanding the characteristics of your soil is such an important part of farming, and from a nutrition management perspective, you should know:
Soil Type – Parent material + texture
Soil Texture – Percent sand, silt, clay, and gravel.
Soil pH – this can wildly affect how available nutrients are in your soils (see table to the right)
Soil Depth – Restricted rooting depth, such as depth to pans
OM – Organic matter plays a critical role in nutrient cycles
CEC –affects how nutrients move (or don’t)
PAW – Plant available water, obviously important
Olsen P – A measure of mostly available P, a major macronutrient, in the soil
Drainage – Important for irrigation and rootstock choices, and can impact leaching
Soil Nutrient Availability – Determines likely nutrient deficiencies/toxicities to address
Slope – affects surface runoff, erosion, and water potential
Some of these soil characteristics are going to be determined by soil testing, while others require on site assessments. Due to the importance of soils there are some great resources available to use as a jumping off point. In New Zealand, Landcare Research has created S-Maps, which is available for many agricultural areas, and while the scale of the assessments is too large to pinpoint exact features of most farms, it does provide a good estimation of what you're working with. In the States, the USDA-NRCS has a similar map system called Web Soil Survey, and UC Davis' California Soil Resource Lab has a great plug in for Google Earth called SoilWeb Earth (links to these pages at the end).
Soil is the ultimate source of nutrition for vineyards. It is a very complex system with many moving parts, which is why it is important to understand some basic characteristics about your soils before making any plan to add ground fertilizer. However well intentioned “feel good” fertilizer applications are towards the vines, unnecessary additions can have some unintentional negative impacts (i.e. acidification, excessive vigour potential, etc.) on the soil ecosystem, and the ecosystems surrounding your farm.
Ways to give back:
There are two basic methods of fertiliser application, soil applied and foliar applied. What is “best” very much depends on what you’re after, what your system is capable of, and the timing of the application. Grapes are designed to actively take up nutrition from the soil, less so through the leaves, however, both are important tools for nutrient management in vineyards.
Rules of Thumb for Fertiliser Applications
Apply with Intention:
Know what you’re after from the fert. Are you wanting to increase vigour? If so, soil based ferts earlier in the season are best so that the vine can take up the nutrition early and grow more.
Recent work in Washington State show that foliar Nitrogen fert after veraison boosted YAN without increasing vigour, and gave an increase in YAN that would have required much more solid fert to achieve (Davadant et al, 2023)
Timing:
Vines in the early season are working almost exclusively on reserve nitrogen, and are not looking to the soil to take up nutrition at budburst.
Postharvest fert can be an excellent option in some circumstances, but how it’s applied, and how long the leaves stay operational on the vine, makes this a higher risk time to apply in terms of nutrient use efficiency.
Vines access nutrients in the soil solution, as soils become drier nutrient delivery to the root surface slows down.
Solid fert:
Takes a longer time to become plant available
Is a concentrated source of nutrition, so application timing is critical to avoid huge losses by either leaching or runoff.
Foliar fert:
Leaf cell uptake of any foliar spray is passive, and relies on the spray either going through stomata, or moving across the leaf’s cuticle and cell walls into the leaf cells themselves; this tends to reduce efficiency or requires specialised formulations.
Requires the appropriate formulation and excellent coverage to have the best effect.
Sprayers should be well calibrated and high water rates used.
Fertigation:
Can be a great way to target application directly to the vines, but this may require you to alter your irrigation set to ensure the fert is pushed where it needs to be and not deeper than required.
Dosing quantity, frequency, and timing are important to consider.
Compost:
Test so you know what you’re applying
Much like whiskey – account for the “angel’s share,” or in this case – the “microbe’s share,” – and apply with the expectation that nutrient availability is less accurate than conventional fertilizers, and that not all the nutrition in the compost will end up available to the vines
Ways In Which One’s Shit is Lost:
Timing, product, application method, formulation, weather, and site conditions play a major factor in nutrient use efficiency of your fertilization efforts. Below are just a few notes on the big 3 – N, P, and K:
Nitrogen:
Nitrate leaching is a major way N fertiliser applications are lost, it can also have an acidifying affect when leached.
Ammonium fertilisers are not really prone leaching, but can acidify soils both by plant uptake and nitrification (which converts ammonium to nitrate)
Incorporating cover crops with high C:N ratios can lock up Nitrogen, when using cover crops it's important to know the impacts of incorporation timing and species C:N ratios.
Using legume cover crops do not always "help" (details below)
Phosphorous:
Surface run off accounts for the greatest proportion of how P fertilisers are lost
Formulation has great impacts on how solid applications become available and interact with the environment
Many vineyards can still thrive in low P soils with the help of mycorrhizal fungi
Knowing the %P Retention of your soils can improve decision making around how much to apply
Potassium:
K can leach, particularly in soils with low CEC (no surprise there)
Plants are more than happy to keep taking up K, over applying can impact wine quality
Applying compost with a substantial amount of grape marc and/or applying grape marc straight after pressing will likely be high in K, which is concentrated in grape skins. A laboratory test on compost, especially if you plan to use a lot, is recommended.
Cover crops:
Cover crops are sown for many reasons, including to help with vine nutrition. While it’s true that leguminous cover crops can fix atmospheric Nitrogen into plant available forms, they do not give up this nitrogen willingly, so the timing and method of their management, and the subsequent release of their fixed Nitrogen, needs to be considered. Legumes have to get all their other nutrients from the soil, and so can be in direct competition with vines for them, ultimately reducing productivity potential in some soils. Also, the symbiosis with Rhizobium bacteria is expensive (in terms of photosynthate demand) for the legume, so if the soil has adequate Nitrogen, legumes fix little, if any, additional. Finally, fixation requires warm soil, so legumes included in a winter cover crop mix likely fix little Nitrogen in cool climates if they are terminated before budburst as is common in frost prone regions. To assess whether fixation is happening, uproot some of the legumes and look for root nodules that are red or pink inside, indicating that the fixation is occurring.
Final Thoughts:
Legislation in New Zealand has put agricultural nutrient management under the microscope to help preserve waterways and ecosystems. While we can all agree limiting our impact on the environment is of the utmost importance, having a thoughtful approach to nutrient management is also a smart business decision. Adding unnecessary fertilizers is not only throwing money down the drain, but also potentially harming the ecosystem and degrading wine quality. However, taking nutrients in large quantities via fruit year after year without providing proper maintenance nutrition to the vines can cause negative yield, quality, and vine health outcomes in the long term. Fertilisation of vines is absolutely critical for long term vineyard success, but without a good plan you can end up doing more harm than good.
Literature cited
Davadant, P., Shcherbatyuk, N., Doyle, R., Harbertson, J., Keller, M. (2023). Impact of soil-applied and foliar-applied nitrogen on grape and wine composition. IVES Conference Series, GiESCO 2023.
Longbottom, M. (Ed). (2009). Managing grapevine nutrition in a changing environment, Research to Practice Manual. Australian Wine Research Institute, Adelaide, South Australia.
Other helpful resources
Web Soil Survey. USDA-NRCS. https://websoilsurvey.nrcs.usda.gov/app/
S-Maps. Landcare Research. smap.landcareresearch.co.nz
S-Maps - Marlborough District Council Access. https://smartmaps.marlborough.govt.nz/smapviewer/?map=eeeff21e2a664dbeba7e07d5b177d593
SoilWeb Apps. UC Davis California Soil Resource Lab. https://casoilresource.lawr.ucdavis.edu/soilweb-apps
Vineyard Underground Podcast: Advances in Vineyard Nutrition Monitoring with Dr. Markus Keller
Williams, L. E. VEN 115 (Raisin and Table Grape Production) Review of Mineral Nutrition of grapevines and Fertilization Guidelines for California Vineyards. https://ucanr.edu/sites/SoCo/files/288481.pdf
NZ Freshwater Farm Plans: https://environment.govt.nz/acts-and-regulations/freshwater-implementation-guidance/freshwater-farm-plans/
Managing grapevine nutrition and vineyard soil health. https://winewa.asn.au/wp-content/uploads/2020/04/Grapevine_Nutrition_LR_2.pdf
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