Effects of inoculation with Frankia on the growth and nutrition of alder species and interplanted Japanese larch on restored mineral workings

The value of interplanting various alder species as a nitrogen-supplying nurse crop to Japanese larch on restored opencast coal spoil was investigated experimentally. Six alder species were inoculated with two strains of Frankia in a nursery experiment, and their performance tested in the field over a 6-year period. Their effect on the growth and foliar nutrition of Japanese larch was also studied. The experiments demonstrate that alders can significantly improve growth, although there is a period of about 5 years before this nursing effect is detectable, corresponding to the time necessary to accumulate nitrogen in the growth substrate. However, compared with other methods for improving spoil nutrition, such as application of sewage sludge, or mixing in organic soil-forming materials, the growth of larch using the alder nursing method is poor.