Chemical Aspects of Heather Burning

Heather burning is widely practised by farmers and gamekeepers in most upland regions of Great Britain. The conditions, if any, under which the practice can be regarded as a sound long-term system of management are not known. Pearsall (1950) and McVean (1959) have discussed the dangers associated with burning but little is known about the effects of burning on soil fertility. When a moor is burnt a large proportion of the plant nutrients contained in the standing vegetation is released in more mobile forms in the ash or in smoke. This paper describes an attempt using laboratory experiments to assess to what extent these nutrients are likely to be lost from the plant-soil system. It covers three major aspects of heather burning: the chemical changes which take place when vegetation is burnt; the effects of rain water on the products of burning; and finally the compensating factors that reduce or make good any losses from the system. In these experiments samples of heather were burnt in the laboratory, the resulting ash was extracted under various conditions and the capacity of the soil to retain the soluble nutrients was examined using soil blocks. The composition of the smoke produced during the burning was also determined.