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Coffee vs. wine

From the August 2019 issue.

In select excerpts from Coffee and Wine: Two Worlds Compared, former United Nations Senior Adviser Morten Scholer compares the growth and yields of the plants behind the two beverages.

From seed to coffee tree
The coffee tree or coffee bush is an evergreen perennial of the Coffea rubiaceae family. It can grow to 10 metres (30 feet) but is usually pruned to less than three metres to make harvesting easier. There are an estimated 17 billion coffee trees in the world.

Coffee trees reproduce primarily from seeds. Reproduction by cuttings of branches, also called shoots, is possible and most successful with Robusta.

To grow coffee plants from seeds, one needs ripe coffee cherries. After removal of the skin and pulp, the seeds (coffee beans still in parchment) are set out to germinate in sand for one to two months. When small stems grow with small leaves, the seedlings are moved to nursery beds and eventually planted in the field after a year. A processed green coffee bean can also be used as seed, but the method is less effective. Natural propagation is mostly a result of birds consuming the coffee cherries and then spreading the seeds with their droppings.

For Arabica, it takes three to four years from seedling to the first full harvest. For Robusta, it may be two to three years only.

Yield per coffee tree and per hectare
One kilogram of green coffee beans requires around six kilograms of fresh cherries. A coffee tree will typically produce around 0.8 kilograms (or two pounds) of green bean coffee annually but yields vary from less than 0.1 to more than two kilograms.

The world average yield for coffee is around 12 bags (60 kilograms each) of green coffee per hectare. That is 720 kilograms per hectare or 640 pounds per acre – based on a harvest of just more than four tonnes of fresh cherries per hectare.

The yield varies from country to country for many reasons. Some are given by nature (like climate, terrain, and soil) whereas others are related to agricultural practices, including choice of variety, pruning, use of fertiliser, renovation through replanting and grafting, planting density, weeding, inter-cropping, irrigation, management of diseases and pests, and harvest methods.

The yields in Brazil have gone up over the years primarily as a result of increased planting density and cultivation practices. They are likely to grow further with irrigation being one of the means. Some Arabica areas with experimental irrigation and optimal use of fertilisers already produce more than 70 bags (4.2 tonnes) of green beans per hectare – even 100 bags (six tonnes) and over, have been mentioned for Conilon (Robusta).

Propagation of grapevines
Grapevines are climbing plants, most of which do not have their own natural support like trees. They can grow in arid regions (just like olives and plums) but are sensitive to climate and sometimes dependent on irrigation.

Grapevines are usually propagated from cuttings – that is, by taking dormant shoots pruned off during the spring. The cuttings are planted in garden soil and grown for a year before they are planted in the vineyard. They will be the same variety as the vine that they were taken from, whereby desired characteristics can be preserved.

When growing grapevines from seed, the new vine may differ from the fruit from which it originated. This is how grape breeders breed new varieties. 

The lifetime of vines varies with grape variety, climate, soil type, maintenance, regional traditions, and other parameters. Vines can grow for up to 100 years, exceptionally more. There are vines from the 1850s in the Loire region in France and Barossa Valley in Australia. A few vines in California are from around 1880. Old vines have a low yield, and both the harvest and wine production are labour-intensive. 

Yield per vine and per hectare
Let’s look at some of the questions often asked about yield: what is possible, what is desirable, what is typical, and what is permitted?

The annual yield per vine and per hectare depends on climate, soil, drainage, grape variety, age of the vines, density of planting, pruning technique, use of pesticides, fertilisers and irrigation, timing of the harvest, and the vinification method. The yield can be measured as weight of grapes or volume of wine.

A vine typically produces what corresponds to one litre of wine per year. But production may be less than half a litre from some vines in Bordeaux and more than five litres in some vineyards in the New World.

Production per vineyard area is measured differently around the world. In Europe it is common to measure and regulate the production in hectolitres of wine per hectare (hL/ha), whereas, in most of the New World it is weight of grapes per area unit.

An easy and rounded conversion is one tonne per acre of grapes equals 17 hL/ha of wine. The conversion factor is slightly lower for white wine (15 to 17 hL/ha) and higher for red wine (17 to 19 hL/ha) depending on the variety of the grapes and the vinification style.

A controlled low yield is generally recognised as a parameter for quality, which is why many appellations stipulate a maximum allowed production of grapes or of wine – for example seven tonnes per hectare or 45 hectolitres per hectare. The actual yield is the result of the density of vine planting combined with the vineyard management, in particular the practice of green harvesting of green berries, also called thinning or dropping of fruit. The relation between crop load and wine quality is a thoroughly studied aspect but the correlation remains unclear.

*The information has been extracted and edited from Morten Scholer’s 330-page book Coffee and Wine: Two Worlds Compared.

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