Influence of soil conditions on grape yield and quality

Grapevine is a flexible crop capable of growing on almost any type of soil. However, the quantity and quality of the harvest depend on soil conditions more than in most other plants. When planning a vineyard, it is important to evaluate not only the plough layer, but also the subsoil horizons and parent rock. The root system of the vine reaches a depth of 2–3 meters or more, so the properties of the deep layers directly affect the development of the vines.

How the physical properties of the soil determine grape quality

Regardless of the region of cultivation and the intended use of the harvest, grapes require light, warm, and aerated soils. They must have good water permeability and a sufficient supply of nutrients. On heavy clay soils and chernozems with a high humus content, yield increases, but the quality of the berries decreases significantly. For table cultivars, this threatens the loss of transportability and storage life.

In the juice of wine cultivars grown on heavy chernozems, the concentration of nitrogenous substances increases. This leads to clouding of the must, impairs the color of juices and wines, and reduces their ability to be stored for a long time. In contrast, light skeletal and gravelly soils improve the storage life of table grapes. Juices and wines from such sites possess a delicate, harmonious taste, a pronounced cultivar bouquet, and high clarity.

Solonetzic sites, soils with excessive stoniness, or a washed-out root-inhabited layer are unsuitable for planting vineyards. Massive chernozems with a high clay and silt content pose a particular danger. On such lands, the root system of the vine is sharply inhibited, and the productivity of the bushes drops. The limiting physical properties of the soil that restrict grape growth must be controlled by the agronomist at the plantation design stage.

• Soil density — above 1.4 g/cm³
• Soil hardness — more than 20 kg/cm²
• Porosity at minimum moisture — 15%
• Wilting moisture — less than 1.2 of maximum hygroscopicity

Rootstock selection and the influence of geographic soil type

In areas where phylloxera is present, the above-ground part of the bush contacts the ground exclusively through the root system of the rootstock. The roots of rootstock cultivars are very sensitive to the soil type, its mechanical composition, and the level of active lime. Excess lime inhibits the plant, so the rootstock is selected strictly according to the structure of the soil profile at a specific site. The correct selection of the "rootstock-soil" pair determines the longevity of the entire vineyard.

When selecting rootstock material for chernozems and forest soils, they are oriented towards their mechanical composition:

• Riparia Gloire de Montpellier — the best option for loamy chernozems;
• Riparia x Rupestris 101-14 — optimal for heavy loamy chernozems and gray forest loamy soils;
• Berlandieri x Riparia Kober 5BB — recommended for soils that are heavier in mechanical composition.

The wide geography of industrial viticulture confirms the high adaptability of the crop. In France, Hungary, Bulgaria, Romania, and the countries of the former Yugoslavia, vineyards are traditionally concentrated on brown mountain-forest soils. In the regions of the former USSR, plantings are located on a wide variety of soil types depending on the cultivation zone.

• Chernozems (ordinary, southern, leached, carbonate) — Moldova, North Caucasus, southern Ukraine;
• Humus-carbonate soils — Crimea, foothills of the Krasnodar Territory, Georgia, Armenia;
• Serozems of long-term irrigation and eroded soils — Uzbekistan, Tajikistan, Turkmenistan, Azerbaijan;
• Chestnut soils — Stavropol Territory, Kherson Region, Dagestan, Zhambyl and Almaty regions of Kazakhstan;
• Sandy deposits of river floodplains and terraces — Chechnya, Dagestan, Bukhara Region of Uzbekistan, as well as Kherson, Mykolaiv, and Odesa regions of Ukraine (including the Lower Dnieper and Lower Dniester sands);
• Sandy massifs of marine origin — Absheron Peninsula (Azerbaijan), Arabat Spit (Crimea), Anapa area (Krasnodar Territory);
• Pebbly soils, yellow soils, and red soils — Fergana Valley (Uzbekistan), individual regions of Georgia.

Aeration and density: how soil structure manages root development

The mechanical composition of the soil directly determines the depth and branching of the grapevine root system. In heavy soils, the vine is forced to overcome high mechanical resistance. As a result, the plant forms thick skeletal roots to the detriment of fine feeder roots responsible for nutrition. Increased soil density inhibits bush development, reduces berry sugar content, and increases juice acidity.

Aeration is no less critical for grapes. With poor air exchange and a lack of oxygen in the root zone, the uptake of water and nutrients drops sharply. Under anaerobic conditions, toxic decomposition products — carbonic acid, organic acids, and alcohols — accumulate in the soil. They damage the root cell protoplasm, depriving it of its semi-permeability and osmotic properties.

The impact of oxygen deficiency has been proven experimentally for all grape cultivars and rootstocks. Popular rootstock forms are particularly sensitive. For instance, the roots of the Riparia x Rupestris 3309 rootstock function normally only when the oxygen content in the soil air is at a level of 19–20%. A drop of just 2% in this indicator slows down the development of the vine fourfold due to a profound disruption of root nutrition.

• Thickness of skeletal roots in heavy soils — more than 4 mm
• Optimal O₂ content for Riparia x Rupestris 3309 rootstock — 19–20%
• Delay in vine development when O₂ drops by 2% — 4 times
• Number of aroma components in juice and wine — about 400

A decrease in soil porosity leads directly to a reduction in the length and mass of grape roots. This problem is most acute in compacted chernozems, which are naturally characterized by low porosity. Under such conditions, vine productivity drops sharply across key indicators:

For this reason, light, well-aerated gravelly and skeletal soils formed on limestone are considered the best for vineyards. They contain a large percentage of stony-loamy fractions. Large gravel on the field surface acts as a natural soil conditioner and creates optimal conditions for the vine:

• accumulates and conducts heat to the roots;
• retains soil moisture and prevents rainwater runoff;
• protects the root-inhabiting horizon from compaction by tractor wheels;
• maintains air voids between stones.

The color of the soil also influences the temperature regime. Dark soils (chernozems and chestnut soils) absorb more solar energy, heating up faster and more intensely than light sandy or calcareous soils. In such areas, the growing season begins earlier, developmental phases proceed faster, and berries ripen at an earlier date.

Chemical composition of the soil and harvest quality

It is traditionally believed that the best grapes for winemaking are obtained on calcareous soils with an alkaline reaction. However, high-quality raw material can also be harvested on acidic soils — everything here depends on the biological characteristics of the cultivar. For example, Riesling, Silvaner, Traminer Rose, and Müller-Thurgau prefer acidic soils. In such an environment, grapes absorb micronutrients more actively (with the exception of molybdenum), whereas macronutrients are absorbed more easily in neutral soils.

Excessive soil fertility is often detrimental to wine quality. High nitrogen content leads to the production of watery juices and wines poor in extract, tannins, and pigments. If nitrogen fertilizers are applied to calcareous soils, the concentration of anthocyanins in the berries drops sharply. A lack of available potassium in the soil also leads to a deficit of phenols and anthocyanins.

The chemical composition of the soil directly regulates the accumulation of proteins and amino acids in the berries. The subtle varietal aroma of the grape, which consists of nearly 400 volatile components, also depends on the type of soil. These substances determine the future organoleptic properties of the juice and wine.

Understanding these patterns protects the agronomist from mistakes when establishing a vineyard. A detailed consideration of the influence of soil factors on the vine is the basis for agro-ecological zoning. This is the main practical tool for the correct selection of plots for specific cultivars.

How to unlock the potential of a cultivar: micro-zoning and selecting a method of propagation

To fully unlock the potential of grape productivity and quality, it is necessary to match the biological characteristics of the cultivar with the specific conditions of the plot as closely as possible. For this purpose, micro-zonal zoning is conducted. The work is carried out on the scale of an ecological-geographical region, a specific farm, or individual plots within it.

In the process of planning plantings, the agronomist solves four key tasks:

• Determines the economic feasibility of commercial grape cultivation in the given zone.
• Selects cultivars based on ripening time and intended use, focusing on the sum of active temperatures and their intensity during the berry ripening phase.
• Selects the cultivation technology: covering, non-covering, or conditionally covering crop, with or without irrigation.
• Compares the requirements of a specific cultivar with the soil and climatic conditions of the chosen plot.

In commercial viticulture, plants are propagated exclusively by vegetative means. The seed method is used only in breeding to develop new cultivars, as seedlings lose the characteristics of the mother plant due to heterozygosity. Furthermore, organisms grown from seed have a long juvenile period, which delays the onset of fruiting.

Practical methods of vegetative propagation and nursery operations

Vegetative propagation of grapes is based on their biological capacity for regeneration. A bush's roots can only reproduce new lateral roots, but growing an entire plant from them is impossible due to the lack of buds. A new plant is formed only from stem segments—cuttings or layers—that carry at least one healthy bud.

In practice, the following propagation methods are used for establishing and renovating plantations:

• Common cuttings. A simple method for own-rooted culture of European-Asian cultivars and phylloxera-resistant rootstocks. For this, cuttings are cut from matured annual shoots—ranging from one- to five-bud cuttings—rooted, and grown into one- or two-year-old nursery plants. Green shoots can also be used in the process.
• Grafted cuttings. This method is based on the grafting of a scion onto a rootstock. Grafting is necessary for the renovation and reconstruction of vineyards and the accelerated propagation of valuable cultivars.
• Layers. Used rarely, mainly for hard-to-root species and cultivars, or for the rapid production of vigorous own-rooted nursery plants in the very first year.
• Meristem of the apical bud. A labor-intensive laboratory method used in research centers for virus-free sanitation and propagation of rare introduced cultivars.

Specialized nursery enterprises are engaged in growing high-quality, true-to-type nursery stock. They are the most important link in the industry, ensuring the establishment of new vineyards. Their main task is the production of nursery plants that strictly comply with commercial standards.

The annual establishment of new table vineyards, the reconstruction of old plantations, and demand from private farms require a constant supply of quality nursery plants. To meet this need, a nursery for own-rooted material requires a reliable infrastructural base. It is important to correctly build the entire technological chain—from vine harvesting to planting in the field.

To grow healthy own-rooted nursery plants, the farm requires the following facilities:

• true-to-type mother plantations of regionally adapted cultivars for harvesting cuttings;
• specialized storage for vine wood and finished nursery plants;
• facilities for pre-planting preparation of cuttings;
• hotbeds, trenches, and an irrigated nursery plot within a crop rotation system.

Complexes for the production of grafted material

The production of grafted nursery plants is technologically more complex and requires more significant capital investment. For this task, specialized grafting complexes are built according to standard or custom designs. They allow for the integration of all stages into a single cycle—from storing scions and rootstocks to the hardening of finished plants.

In addition to rootstock and scion mother plantations, a modern complex requires complex engineering infrastructure. The central element is the main production building, where key technological processes are concentrated. All rooms must be logistically connected for efficient handling of plant material.

Such a complex must include:

• storage facilities for rootstock cuttings, scions, and finished nursery plants with a compressor station for refrigeration units;
• facilities for pre-grafting preparation of grafting components;
• a grafting workshop, a block of stratification chambers, and a waxing station in the main building;
• glazed greenhouses with hydroponic sections for the accumulation and hardening of grafts;
• a warehouse for storing equipment and tools, as well as an administrative and utility block.