A shortage of suitable equipment could mean that only half the level of forest fertilisation that should take place this year in Finland will be realised, according to the Finnish Forest Association.

The association said up to 60,000ha should be fertilised in 2007. But only four helicopters are currently used for the task, making it difficult to increase the area of fertilisation.

During good weather, a helicopter can spread up to 50 tonnes of fertiliser a day.

Forest fertilisation became common in Finland during the 1960s and reached a peak in 1975 when 244,000ha were fertilised. The rate then gradually dropped due to a number of factors, including the end of state subsidies for fertilisers.