Interactions of nitrogen fertilizers and forest humus—II. Beech and oak

摘要: Abstract Laboratory incubation experiments with and without added urea or NH 4 NO 3 were performed on humus from stands of beech ( Fagus silvatica ) grown soils limestone, schists, flysch peridotites oak Quercus conferta limestone schists. Beech showed considerable nitrification a concurrent high mobilization rate the nutrient elements Ca, Mg K, especially in presence increasing concentrations, but no net N mineralization was observed. schists concentrations did not modify their inability to nitrify. Non-nitrifying types ammonification K rates about one-tenth those observed nitrifying inversely correlated concentrations. Exchangeable Al 3+ extractable Mn present underlying inorganic all cases where absent overlying addition 500 parts 1000 Mn/10 6 separately combination failed inhibit nitrification. An interpretation these findings is attempted reference possibility absence climax vegetations preference certain forest species for + − .