Jatropha is a cross-pollinated crop. This means that the pollen of one plant is transferred to another plant. This is achieved by bees and thus you will see bee­hives at Jatropha plantations. Any genetic improvement is strongly linked to the number of plants per acre or hectare. This is called the "plant population.”

Too many plants per hectare do not necessarily increase yield and profitability. Seed costs and soil fertility are to be considered. An optimal plant population for Jatropha production is one that maximizes both yield and profitability. There is a maximum of plants a plantation can bear. With too many plants per hectare the yield and, therefore, profitability will decrease. So far the optimal plant population for Jatropha has been found to be between 1600 and 2200 trees per hectare. The big challenge for maximum profitability is to concentrate research on the breeding and multiplication of plants that have the following proprieties:

• Resistance against pests.

• Optimal growing rates.

• High oil yields.

• Minimum rainwater use.

On a small scale, in several parts in the world Jatropha plants have been bred with an oil yield of 7 tonnes per hectare — triple the yield of the well-known varieties.

3.1.15