A term used to describe the yield of grapes at harvest, usually expressed in hectolitres of grape must or wine per hectare or in kilograms of grapes per hectare. Overseas, tons/acre is also commonly used. This is also used as a wine-law specification, expressed as a maximum yield in hectolitres per hectare, for certain wine quality levels and can vary greatly depending on the country, wine-growing region, individual sites or even certain wines. With regard to vine density, there has been an extreme reduction over the last two millennia. The Romans still recommended 50,000 vines per hectare; this ruled out mechanical treatment of the vineyard from the outset. In the middle of the 19th century, the density was still 20,000 vines per hectare on average, with yields not exceeding 40 hectolitres per hectare. Today, the vines are planted at a distance of 1.5 to 2 metres from each other (this varies from country to country and wine-growing region, and also depends on any regional regulations).
In general, it is customary to plant an average of 5,000 vines per hectare (see under Form of cultivation). On a rough average, a vine for yield-reduced quality wine yields 1.5 to 2.5 kg of grapes, which results in 1.5 to 2 bottles of wine with 0.75 l each. For specialities or predicates, such as Beerenauslese, Trockenbeerenauslese or Eiswein, the yield is considerably lower. For the grape varieties cultivated in Germany and Austria, one can expect an average of 55 to 75 litres of must from 100 kilograms of grapes at normal ripeness. The yield and grape quality in the vineyard is controlled by the winegrower through various measures throughout the year, including pruning and leaf care, as well as thinning out (green harvest) and grape splitting or grape breakage.
The yield is calculated using the following formula: average number of grapes per vine x average grape weight in kg x number of vines per hectare gives the yield in kg/ha. A more precise formula, taking into account specific values, can be found on the website "Dienstleistungszentren Ländlicher Raum Rheinland-Pfalz": (pruning [eyes/vine] x budding rate [%] x average number of grapes/vine x average grape weight [g/vine] x number of vines/ha) / 1000 = yield [kg/ha]. An example is (12 eyes/vine x 90% x 2.2 grapes/shoot x 120 g/grape x 5000 vines/ha) / 1000 = 14,256 kg/ha. The specific values per grape variety/vine, such as weight/number of grapes, are given under the keyword grape.
The yield is one of the most important factors influencing the production of top wines. As a rule, lower yield quantities also result in higher qualities. A surplus yield of grapes has a negative effect due to mostly too little sugar, colorants and aromas. So do high yields therefore mean poor quality in principle? To be precise, the "right" relationship between quantity and quality is not completely clear and is also strongly dependent on other factors such as soil type, type of cultivation, density of planting, relationship between the amount of leaves and grapes, grape variety with its rootstock and the type of pressing. However, not only the number of vines per hectare, i.e. the density of planting or the space available per vine, especially for its roots, has a great influence, but also the yield per vine.
In the Grand Cru locations in Champagne, Bordeaux and Burgundy, the vines often produce only half a kilogram of grapes, but up to 10,000 vines per hectare stand in very narrow rows. Such a high density can also be found in the German Moselle wine region. It is a fact that in Bordeaux red wines from Cabernet Sauvignon can produce top wines at relatively high yields, but in Burgundy the qualities from Pinot Noir are problematic at yields of more than 50 hl/ha from hillside sites. So even relatively high yields can produce good quality. For the production of simple consumer wines or distillates, however, mass producers (varieties with high yields) are deliberately used.
A list of maximum wine yields per hectare in descending order: Soave 140 hl, Chianti 100 hl, Rheingau 84 hl, Barolo 80 hl, Brunello di Montalcino 80 hl, Austria for all areas 67,5 hl, Champagne 60 hl, Rioja 60 hl, Beaujolais 50 hl, Saint-Émilion 45 hl, Pomerol 40 hl and Priorato 10 hl. Individual producers set themselves particularly low limits, significant examples are the French wineries Domaine de la Romanée-Conti with 25 hl and Château d'Yquem with 9 hl, and the Spanish winery Dominio de Pingus with 12 hl per ha.
The wine market organisation adopted by the EU in 1999 obliges the member states to set a permissible yield per hectare for each quality wine in quantities of grapes, must or wine, taking into account the yields of the ten preceding years, with only those vintages that are satisfactory in terms of quality being taken into account. The countries may fix yields differently according to the criteria of production area or part of the production area, vine varieties or groups of vine varieties and quality groups under their own responsibility. The excess quantities may not be placed on the market.
Not only within the EU, but in most wine-growing countries, yield limits are an important criterion for the classification of wines within quality systems. This can also vary per wine-growing region, wine-growing sector or, as in the Romanic countries, per appellation. But how can compliance be checked? Apart from the fact that quality-conscious producers themselves have a strong interest in achieving a reduction in yield through targeted measures, control is carried out by wine authority institutions. Of course, the authorities cannot, however, carry out on-site inspections of all producers during the grape harvest. As an example, the custom in Austria, which is similar in many countries, will be explained here. The Austrian Wine Act 2009 defines the quantity restriction:
§ 23 (1) Winegrowers (managers of vineyard areas) may not market more than the maximum quantity per hectare of agricultural, quality or special quality wine or of grapes intended for their production per harvest of a vintage year. (2) The maximum quantity per hectare shall be 9,000 kg of grapes or 6,750 litres of wine per hectare of vineyard area entered in the vineyard register and planted with vines for the production of country, quality or special quality wine. 3. If the maximum quantity per hectare is exceeded, the entire quantity harvested may be marketed only as wine without a vine variety or vintage designation. The verification:
Every year, a harvest declaration must be made by each holding by the 30 November deadline. On this declaration, the quantity harvested can be seen for the quality grades covered by the hectare yield regulation. In connection with the stated total wine-growing area of the holding, the BKI authority calculates whether the maximum yield per hectare has been complied with. The above-mentioned sanctions apply if the maximum yield is exceeded. This sounds very rigorous, but in reality it is far from extreme. This is because the harvest declaration can be divided into wines with and without a maximum yield per hectare (formerly table wine). Thus, a holding that harvests more than the 9,000 kg/ha in total would only have to "sacrifice" a "partial quantity" with a corresponding area for the "wine from Austria" (for which there is no yield limit).
In addition, the calculation of the maximum yield per hectare is based on the cultivated area under vines (sum of productive and infertile areas). This means that the young plants that have no or little yield are also included. Furthermore, the maximum yield per hectare is the same across all quality levels (max. 9,000 kg/ha). This means that a Prädikatswein producer who, for example, harvests 3,000 kg of a Trockenbeerenauslese on one hectare can therefore harvest 15,000 kg on his second hectare. That is a total of 18,000 kg on two hectares, without exceeding the permitted value. As already mentioned, however, quality-conscious producers often fall far short of the yield restrictions.
All aids, work and measures in the vineyard during the vegetation cycle can be found under the keyword vineyard care. Complete lists of the numerous vinification measures or cellar techniques, as well as the various types of wine, sparkling wine and distillate regulated by wine law are included under the keyword vinification. Comprehensive information on wine law can be found under the keyword wine law.