A rule-of-thumb by Dr. Raymond Keogh
I feel that the debate on growth rates of teak has gone on too long; growth rates for this species are well known and it is time to make this abundantly clear!
The question of growth rates in teak plantations has become a contentious issue in recent times. It is of crucial importance to teak growers and investors because timber production forecasts and financial returns depend on accurate predictions. Fortunately, we know more about teak growth rates in plantations than any other tropical hardwood. Growth and yield studies began in earnest last century and continue today. Growth is normally expressed in terms of cubic metres per hectare per year and highest growth rates are normally expressed in terms of maximum mean annual increments (note: maximum current annual increments, which are higher than mean annual increments are not normally used in timber forecasting as they would produce erroneous predictions over the life of the crop).
A very tolerable rule-of-thumb can be applied across the tropics regarding highest growth rates in teak plantations. This rule-of-thumb does not change for wide definitions of stem volumes.
Growth rates which exceed an average of twenty cubic meters per hectare per year in twenty years are unlikely to be encountered.
In other words, only in exceptional circumstances will the total production of stem woody material exceed four hundred cubic metres in twenty years. Growers and investors must base their predictions on averages and not exceptional growth rates. Most practicing foresters in the tropics would be content to encounter an average annual growth rate of ten to fifteen cubic metres per hectare per year over twenty years on all their plantation sites. Through good site selection and the planting of genetically improved seed, growers can boost averages and avoid poor producing sites.
Genetic improvement may boost growth but is an expensive long-term activity. Growth may also be boosted in some cases by fertilizer application, but the identification of the necessary chemicals and their optimum rates of application are not fully understood. At the present state of development in teak, it would be unwise to expect that average growth rates can be boosted to reach or surpass the maximum rule-of-thumb growth rate for teak throughout the tropics. Even if it were possible to do so, it would be wise to have a clear understanding of the effects of this increase on wood quality.
Raymond M. Keogh
1 May 1996