Coffee trees, particularly arabica, have a biennial bearing cycle that can result in alternate heavy and light crops. This of course affects farmers' annual incomes but the overall impact is very difficult to measure…

Depending on the overall supply and demand situation at the time a really low 'off-year' crop in Brazil (arabica) or Vietnam (robusta) could well affect global output and, therefore, also prices. It should be remembered however that coffee production is spread over a large number of countries, each with individual production patterns. Therefore, one cannot really speak of global 'on' or 'off' years but, biennial bearing in important producing countries certainly features in global coffee production and pricing discussions.

Some background to the biennial bearing phenomena itself:

In a year of heavy cropping most of the available carbohydrate produced by photosynthesis is used by the developing crop, and little is available for the formation of new wood (suckers) to bear the next crop. In the following year that situation is reversed, with only a small proportion of the available carbohydrate being required for the crop and most of it being available for new extension growth. This then results in a heavy crop in the following year and so on. This pattern of overbearing followed by poor fruit setting is particularly evident in unshaded coffee and occurs independently of climatic conditions. However, changes in rainfall patterns can produce similar effects: heavy crop this year - little next year..

Careful pruning can minimise the impact of biennial bearing by maintaining an acceptable ratio of leaf to crop and ensuring that sufficient new suckers are produced. Shaded coffee, grown under ideal conditions in the tropics or near the Equator, will present much less of a problem (if any) than coffee grown under more stressful conditions. As already mentioned however, coffee production conditions vary greatly throughout the coffee producing world and many individual factors affect crop yields. And, none are unique to all growing areas…

Biennial bearing and production *

The table below clearly shows 'on' and 'off' years in Brazil, whereas there is no discernable pattern for either Colombia or Vietnam. To note however that Brazilian production of Conillon robusta is relatively unaffected by biennial production changes - the fluctuations shown below are mostly due to fluctuations in Brazilian arabica production. * Only the three most important producing countries are reviewed with particular emphasis on Brazil - the world's largest producer.

Coffee production by crop year

So, does the market take into account the biennial pattern? Yes - but only nominally in that it knows the cycle is a fact of life but it reacts more to actual short-term forecasts, or changes in the flow of coffee on to the market, than to the fact that it will be an on or off year.  Can that be disentangled? Not really - it is an ever-present consideration and thus must be factored into the market at some point but it is a bit like background noise - it may always be there but one only really notices it when it is significantly different.

To end, we would summarise that, yes, biennial bearing does impact on the global coffee scene but - the overall impact is extremely difficult to quantify. To do so with any accuracy requires far more statistical and analytical resources than are available to www.thecoffeeguide.org.

Posted 21 January 2009