Bulk density, total contents of N, P, K, Ca and Fe and field- and laboratory-incubated mineral-N were determined for a bog and fen site 3 years after drainage treatments (3 m and 15 m ditch spacings), tilling treatments (untilled, tilled) and fertilization treatments (unfertilized, PK- fertilized), as well as for adjacent untreated (undisturbed) areas of the bog and fen. Tilling of the surface or fertilization did not significantly affect total nutrient contents in either bog or fen, although nutrient contents were generally higher in fertilization or drainage treatments that included tilling. As a result of decreased ditch spacing (from 15 m to 3 m), bulk density was significantly increased in the bog site (from 44.9 to 63.5 mg cm-3) and decreased (non-significant) in the fen site (from 105 to 89 mg cm-3). Total P and K were increased where PK was applied as fertilizer. In bog peats, bulk density (mg cm-3), total N concentrations (mg g-1) and total contents (kg ha-1) of N, P, K, Ca and Fe were significantly higher in the 3 m ditch spacing than in the 15 m ditch spacing. Thus, increases in total nutrient contents in bog peats can be attributed mainly to increased bulk density as a result of drainage treatment. In contrast, bulk densities and most nutrient contents of fen peats were not significantly affected by treatments. However, total N concentrations and total N contents were significantly reduced by more intensive ditching (3 m ditch spacing). Contents of mineral-N in fresh peat and field-incubated and laboratory anaerobically incubated (30°C) peat consisted entirely of NH4-N. Laboratory incubations over a 20-week period demonstrated a high potential for release of NH4-N in peat from treated sites of bog and fen. During four 28-day field incubation periods, production of mineral-N varied from 0.1 to 1.2 kg ha-1(net mineralization) to -0.1 to -0.3 kg ha-1(net immobilization) for bog peat. Similarly, on the fen site production ranged from 0.1 to 2.7 kg ha-1(net mineralization) and -0.1 to -1.7 kg ha-1(net immobilization). In the unfertilized and PK-fertilized treatments of the fen, as well as the PK- fertilized treatment of the bog, net immobilization predominated during the first incubation period, followed by net mineralization during the next three incubation periods. In the unfertilized treatment of the bog, net mineralization predominated early in the growing season, followed by net immobilization thereafter.
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