Results and experience from amelioration trials in Scots pine (Pinus sylvestris L.) forests of Northeastern Bavaria

In southern Germany slow-growing pine forests occur on podzolic soils. They may be naturally poor in nutrients (Ca, Mg, P and N) and/or degraded by human interference (causing mainly N-losses). Comprehensive amelioration experiments initiated between 1960 and 1964 were evaluated after 17-20 years. Repeated fertilization with N alone induced P and Mg deficiency on soils low in these elements. Therefore NPMg(K) - fertilization is now recommended in combination with moderate liming. The latter procedure is aimed towards stimulating organic floor turnover and counteracting possible adverse effects of acid deposition. Repeated N dressings as nitrochalk proved to be preferable to N-cyanamide and to lupin undergrowth as an N source for improving the N economy of the pine ecosystems, CaPKMg being supplied equally in both cases. The former procedure improved the nutritional status and growth of pines effectively and without delay, and increased soil fertility without causing major losses of humus and nitrogen. Underplanting of lupins on the other hand, although enhancing soil biological activity impressively, caused considerable damage to pine roots as well as humus losses, and improved nutrition and volume growth of pines only after a prolonged lag period.