How should you fertilise a vineyard?

Fertilising is about providing the soil with substances – either organic or inorganic in nature and natural or synthetic in origin – that nourish plants and help to improve soil fertility, that is, the overall physical, chemical and biological properties of the soil.

Strictly speaking, however, it is important to distinguish between fertilising and manuring, which here in Italy can be described using the same word “concimare”. Fertilising is a generic term that means “providing the soil with substances that improve its fertility” and fertilisers are divided into manures, soil improvers and conditioners. Manures provide the nutrients that plants need, and therefore affect the chemical properties of the soil. Improvers provide organic substance and thus modify the physical properties of the soil, particularly its structure. In this article on fertilising the vineyard, we look at fertilisation in a broad sense that also considers both manures and soil improvers.

Fertilising the vineyard

Fertilising the vineyard is aimed at giving back to the soil what the vines have absorbed from it. That is to say, the nutrients that the plants consume in larger quantities (called macro-elements, particularly nitrogen, phosphorus and potassium) and also in minimal but essential quantities (micro-elements, such as iron and boron). When you harvest grapes, you actually deprive the vines of the elements they assimilated in order to grow and produce the fruits. The same is true if you prune vines and then take away the cuttings, rather than shredding them and leaving them in place.

If the nutrients are not replenished, over time their scarcity manifests itself in the vines through specific symptoms that are often visibly recognisable, and which depend on the type of deficiency. Of course, the negative effects of nutritional deficiencies are also apparent in the reduced quantity and quality of the grapes. On the other hand, over-fertilisation doesn't benefit vines (or the environment) either. In the case of nitrogen, for example, it leads to more vigorous growth, which in turn increases the plants’ vulnerability to disease and parasites (here you can find our focus article on some of the main enemies of vines: powdery mildew and mealy bugs).

There are several types of vineyard fertilisation with respect to the life cycle of the vine. Basal fertilisation is done before planting the rooted cuttings (vine seedlings) and is followed by annual fertilisation, including nursery fertilisation for the first 2-3 years and production fertilisation from the third/fourth year onwards, once the vines start producing grapes.

Basal fertilisation (or, in the second instance, production fertilisation) requires a preliminary analysis of the soil to ascertain its characteristics, including its texture, the content of organic matter and various chemical elements, etc. During the production phase, it is advisable to repeat this analysis every five years. Whilst this attention to detail is essential for a winery business, it’s overkill in the case of family vineyards or orchards containing just a few vines. To get a rough idea of the properties of the soil in your locality, you can consult zoning studies promoted by wine protection consortia and other such bodies, for example.

Before planting a vineyard, one of the decisions you need to make is which training system to use. The most widespread system is the espalier method, in all its variations: here you can find guidelines for creating an espalier vineyard.

When and how to fertilise the orchard

Basal fertilisation provides a reserve of nutrients that will be useful to the vines in subsequent years. How should you fertilise the vineyard when planting it? Simply add organic fertiliser, i.e. fertiliser of animal and vegetable origin such as manure or mature compost, into the holes where you plant the cuttings. Manure and compost provide the soil with organic matter and fertilise it, transforming into readily available and reserve nutrients through the respective processes of rapid and slow mineralisation. At this stage it makes no sense to apply mineral nitrogen fertiliser, because it would be lost due to leaching.

Nursery fertilisation supports the plants’ early growth, before they become productive. It allows the vines to overcome the stress of transplanting and to take root, resume vegetative growth after winter, and gradually prepare to produce grapes. Therefore, for this type of fertilisation, the fertiliser should be rich in nitrogen, which is a decisive element in the development of plants (roots, leaves, etc.) and in their production cycle.

Production fertilisation is performed on vines during their entire productive life, from the initial stages through to veraison, harvesting and beyond. Just as with a farm vineyard, for a small domestic vineyard it is necessary to work out how much and when to fertilise based on the environmental conditions and soil characteristics. By means of a series of rather complex calculations – effectively a nutritional evaluation of the vineyard – you can estimate how much to fertilise: it depends on the consumption of nutrients by the vines and how many nutrients are lost (through leaching, volatilisation into the atmosphere, etc.). You then need to take into account factors that influence the absorption of nutrients, such as the texture, pH level and organic content of the soil. Another important factor is the availability of water, in the form of rain and irrigation, because plants actually absorb nutrients when they are dissolved in water present in the soil (circulating solution). Conversely, it is inadvisable to use mineral nitrogen fertilisers during very rainy periods.

In order to work out when to fertilise your vineyard, you need to achieve the right balance between the times of the year when the vine roots assimilate nutrients and the phases in which the plants need them most. Although it varies from one chemical element to the next, in general it can be said that absorption peaks in late summer/early autumn, after the grape harvest, and in spring, between vegetative recovery and flowering: these are the optimal periods for fertilising the vineyard.

If you don’t like the idea of complex calculations, you can simply fertilise a vineyard during its productive phase with organic soil improvers, such as manure and compost, or organic nitrogen fertilisers such as pelleted (i.e. dry) chicken manure. Besides improving the soil, manure and compost act as slow-release fertiliser, while chicken manure is a fast-release fertiliser that is extremely nutrient-rich. Another organic nitrogen fertiliser you can use is pelleted animal manure, which performs a fertilising and soil-improving action at the same time. Fresh animal manure performs the same functions, but is not as readily available or practical to use.

Autumn fertilisation of the vineyard helps vines accumulate reserves to better resist the winter and to expend when budding the following spring, because it brings forward the consumption peak of nitrogen (as well as of magnesium, manganese and sulfur) with respect to the absorption peak. So in autumn, you can fertilise the vineyard with organic soil improvers that slowly release nutrients into the soil, then in spring use nitrogen fertilisers – which are faster-acting – to support foliage growth and the preparatory stages of production, bearing in mind that the plants’ biological activity during the resumption of vegetative growth is fuelled by nutritional reserves formed thanks to autumn fertilisation.

Vineyard fertilisation should also take into account crop care and soil management. When you finish pruning the vines, if you shred and bury the cuttings – respectively with a flail mower and rotary tiller – it will provide a source of both organic matter and macro- and micro-elements for the vineyard soil. Furthermore, planting grass cover either throughout the vineyard or only between the rows contributes significantly to the supply of nutrients (nitrogen in particular), and production fertilisation further supplements this supply. Manage grass cover by mowing it with a brushcutter, flail mower, garden tractor or even a lawnmower, if you have a single plant or a vine arbour in the garden, then leaving the clippings in place. In the space of 4-5 years, a grass-covered vineyard can become practically self-sufficient in terms of soil nutrition.

Are you interested in growing your own food? Cultivating a vineyard, vegetable plot or orchard, is a first step towards food self-sufficiency.