Vine fertility/nutrition and composting

Photo credit: Vineyards at Dodon

Introduction

Regenerative viticulture practices can provide vines with the necessary nutrition by improving soil organic matter, offering organic or biological soil amendments often in the form of composts, and supporting the development of symbiotic relationships between vine roots and microbiomes. 

The annual removal of crops and prunings can deplete nutrients from the vineyard, reducing their availability within the ecosystem.  

Vineyards that rely solely on synthetic fertilizers to address nutritional issues can create a short-term feedback loop that: 

  • Damages the vine’s natural mechanisms for obtaining nutrients from the soil because the vine no longer needs to sustain symbiotic relationships between the vine roots and the soil microbiome; and 
  • Fails to replace lost soil organic matter. 

In such cases, it can become necessary to provide increasingly larger inputs of synthetic fertilizers to sustain vine and grape development. 

In detail

Mineral nutrition is crucial in grape production, affecting vine growth, berry development, maturation, and ultimately juice composition for winemaking. The mineral nutrient requirements of grapevines vary based on the variety, the type of rootstock, vine age, and production levels.  

Mineral nutrients are removed by the crop and through pruning, but some, like nitrogen and phosphorus, are potentially removed in much larger quantities. Nutrients can also be lost below the root zone through leaching and to the atmosphere through denitrification. Most of the biomass (shoots and leaves) produced annually by grapevines remains in the vineyard, releasing mineral nutrients back into the soil as it decomposes.  

How does regenerative viticulture address vine nutrition?  

Regenerative viticulture practices attempt to leverage how vines obtain nutrients through natural processes. Understanding these processes is vital to transition away from synthetic fertilisers. The three main pathways are:  

  1. Ionic exchange: Plants actively seek to cultivate beneficial bacteria and fungi by releasing 30-40% of the root exudates (sugars, amino acids, and other organic compounds) they produce through photosynthesis into the soil profile around their roots. This encourages the proliferation of bacteria and fungi who decompose organic matter and release nutrients from the sands, silts and clays in the soil profile. These bacteria and fungi are subsequently consumed by predator organisms – protozoa and nematodes. When the predators excrete their waste, e.g. excess nitrogen, plants can absorb these nutrients through their roots.
  1. Mutualistic exchange with endo- and ecto-phytes: Approximately 90% of plants, including vines, partner with mycorrhizal fungi – either endophytic (within the root itself) or ectophytic (around the root). These fungi form a mutualistic interface between the plant, soil, other plants and the rest of the soil food web through their extensive network of hyphae which can extend a plant root zone by 10,000 times. The mycorrhizal fungi will actively translocate nutrients for the plant in return for additional exudates to support their own growth.
  1. Rhizophagy: Plants are not vegan, they feed on microbes that are present in the root zone. They do this by the release of exudates that encourages their proliferation in the root zone. Endophytic microbes subsequently enter the root and are bombarded with a superoxide produced by the plant which oxidizes their cell walls and causes them to leak nutrients directly into the roots! The plant gets a tasty meal and any remaining bacteria escape through the root hair to feed and reproduce on more exudates.

What is the issue with synthetic fertilisers?  

There are several fundamental issues with the use of synthetic fertilisers.  

  • Synthetic fertilisers disrupt soil microbial activity. Fertilisers provide plants with readily available nutrients reducing the need for plants to form symbiotic relationships with microbes. The reduction of root exudates leads to a decline in microbial populations crucial for the natural cycling of nutrients in the soil and provision of nutrients in a plant available form.
  • Synthetic fertilisers do not replace lost soil organic matter and accelerate loss of organic matters. Synthetic fertilisers, particularly those high in nitrogen, can increase the solubilisation of organic matter. This make organic matter more susceptible to being leached away into water courses. Fertilisers often promote rapid mineralisation and breakdown of organic material without replenishing it, which over time reduces soil organic matter content. This degradation impacts soil structure and fertility, ultimately requiring increasing amounts of fertilizers to compensate for the loss of organic matter and fertility.  

What to do?

  1. Assess your plants and your soil 

It is important to know what nutrients are in your vines and soil, where there might be deficiencies or excesses and understand the status of microbial communities.  

Consider the following analyses:  

  • The nutrient status of the vine, through sap analysis 
  • The nutrients in the soil, through soil analysis 
  • Which nutrients are not being taken up by the vine from the soil 
  • Soil microbiology – particularly fungal to bacterial ratios, protozoan and nematode communities.  

You are then able to assess the causes of any nutritional deficiencies and non-synthetic fertiliser tools available to optimise nutritional uptake. This testing will give you a baseline to verify the efficacity of any measures that you put in place. 

  1. Develop a regenerative soil strategy 

There are many different options to adopting a regenerative approach for your soil, but broadly your goals should be to leverage the way vines naturally seek nutrients by: 

  • Increasing the soil organic matter content 
  • Increasing the quantity and diversity of microbes in the soil 
  • Improving soil structure and water holding capacity  
  • Enhancing plant available nutrients and plant uptake of these nutrients.  

Other regenerative practices such as no tillage, cover crops or the use of animals in the vineyard should also form part of your regenerative soil strategy.  

  1. Purchase or create compost or other microbial inoculants 

There are numerous compost solutions available: 

  1. Buy municipal or commercial compost. Usually readily available and relatively cheap per tonne. But it’s important to verify the quality of any commercial compost both in terms of nutritional composition and microbial life before application. Poor quality compost can contain plant pathogens, plastics and toxins which could affect vine health.  
  1. Make thermophilic compost on site. High quality compost can be made use vineyard prunings, winery waste, farmyard manure, grass cuttings and other locally available materials. It’s important to get the right balance between C:N materials and to monitor the compost temperature during the production process. The compost pile temperature must exceed 55C and be turned multiple times to ensure all parts of the pile have been through a thermophilic process which kills pathogens. Well-made thermophilic compost can be ready in as little as 90 days and is a fantastic microbial inoculant for aerated compost teas.
  1. Take part in community composting. There is an rise in community composting programmes and schemes where organisations collect food scrap waste from restaurants, vineyards, farmers markets, stadiums, etc, using the waste to create compost and provide that to vineyards.
  2. Set up a worm composting (vermicompost) system. Worm composting systems are effective way to manage organic waste, transforming it into high quality, microbial diverse compost. The gut of the earth worm contains many beneficial bacteria and the resulting worm castings are potentially high in N, P, K, Ca, Fe, Zn and Mn, as well as protozoa which will help soil food web nutrient cycling. Manure, food waste and kitchen scraps can all be composted in a vermicompost system. Vermicompost systems can be scaled to match the size of the vineyard. For example, an old bathtub could provide enough vermicompost for 1-2 hectares when used to produce aerated compost tea. Large continuous through flow systems can produce tonnes of worm compost per year. Vermicompost can also be bought from commercial suppliers. Worms can also be used to filter winery wastewater, providing vermicompost.
  1. Build a Johnson-Su bioreactor. Johnson-Su bioreactors create a microbially diverse BEAM (biological enhanced agricultural management) compost rich in P solubilising and free-living & symbiotic N fixing microbes. These compost systems can be built with readily available materials (wire mesh, landscape cloth, irrigation pipes). Applications of BEAM compost have been shown to increase soil carbon sequestration by up to 10.7 tons per hectare which, if applied to 40% of arable land could sequester a significant amount of anthropogenic CO2.
  1. Brew aerated compost teas. Aerated compost teas can be used to increase the number of beneficial bacteria, fungi, protozoa and nematodes from existing on-site composting systems without the need to source significant amounts of compost materials. For example, a 1000 litre compost tea brew that could cover several hectares can be produced with 10-20kg of high quality, microbially diverse compost, vermicompost or Johnson-Su compost.
  1. Identify other nutrient amendments to address mineral deficiencies. There are other commercially available products such as liquid seaweed (kelp), fish hydrolysate, and rock dusts that can be used to address specific mineral imbalances. For example, kelp is one of the best sources of manganese that could address manganese deficiencies when applied as a foliar spray.
  1. Apply amendments to the soil and the vines.  

Compost amendments can be applied to the under-vine strip using a side discharge spreader. Application rates per hectare will depend on the results of your initial analysis and objectives of your regenerative soil strategy. Compost does not need to be worked into the soil as the soil microbial communities can do the job for you. In fact it is better not to invert the soil.

Aerated compost teas can usually be applied using existing spray equipment, either as a foliar treatment directly on the vines or to the vineyard floor. Frequency of application of compost teas is likely to depend on the results of soil mineral and nutrient tests, microbial soil analysis and plant health assessments, but could between 14-30 days throughout the growing season.   

  1. Monitor progress and evolve your strategy over time 

As it takes time to build or rebuild soil health, it is essential to have soils and petioles (or whole leaves) tested and to get advice from an agronomist to ensure there is an optimum nutrient balance for the vines’ growth and productivity. 

There is a lot of research and development being conducted into biostimulants to replace synthetic fertilisers. This includes black soldier fly larvae frass.

Further information

Compost, teas and Johnson-Su
Fertility through cover crops
Worms
Biochar
Biostimulants

Toolkit

Certification

To certify or not to certify? And if you do want to certify, which one to choose? Here we list the schemes that are certifying vineyards as regenerative

Glossary

Regenerative viticulture has a whole vocabulary of terms associated with it. This glossary defines the top 100 terms.

Monitoring soil health

Monitoring soil health is essential to improve your soil health. Lab tests every three years can show trends over time. Tests for soil structure can be performed in the vineyard

Soil organic matter

SOM is an important biological property, the essential food stuff for the soil food web. Minimise losses by minimising tillage. Increase through compost, cover crops, mulch

Interrow management

Tillage exposes the soil to the air, leading to carbon lost to the atmosphere. Native species or cover crops can be managed by mowing, crimping and rolling, grazing

Undervine management

Undervine tillage damages soil biology. Vineyard context will determine the most appropriate alternative for managing this more challenging area

Decompaction

The best way to avoid poorly performing compacted soils is to develop a healthy soil biology: minimise vineyard passes, use plants with deep root systems and encourage earthworms

Soil/ground cover

A key principle is to avoid bare soils. Ground cover reduces soil temperature/evaporation. Living ground cover maximises photosynthesis, provides habitat and biodiversity, helps store carbon

Cover crops

Soil life depends on having things growing and living in it. Selection and management of cover crops is context-specific, preferably native species, direct drilled to minimise soil disturbance