Research made at the Lund University, Faculty of Engineering in Sweden proves that fertilizing spruce with ash increases growth by an average of 14 %.
Mr Gunnar Thelin, manager of the research project, finds the results more positive than expected. He believes the most likely reason for increased spruce growth to be that ash improves the phosphorus balance of the trees.
The researchers examined ash treated surfaces in 23 different locations in Southern Sweden. Self-hardening crushed ash from heating plants was used in the project. The ash was spread by means of a forwarder connected to an ordinary centrifugal distributor.
The results were examined seven to eight years after spreading the ash. They demonstrate the increasing importance of compensating for the increased collection of felling residuals, i.e. branches and tree tops. Even though ash counteracts acidification the amount of ash used is not sufficient to make the ground less acid in the short term. Fall-out of sulphur has decreased considerably; it is no more than 10 % of the quantity 15 years ago, but there is still a lot of sulphur in the ground. It will take decades for the acidification from sulphur to disappear completely.