Irreversible Loss of Organic Soil Functions after Reclamation

After drainage, organic soils change their basic functions from natural carbon sinks and water reservoir to sources of greenhouse gases and water-deficient bodies. The natural process of carbon sequestration is paludification; with drainage and aeration, the organic soil undergoes the irreversible moorsh-forming process (MFP). The intensity of MFP is shown by morphological and structural transformations, enrichment in humic substances, changes in mineral composition, as well as shifts in microbial populations, mesofauna and earthworm species. The climatic impact 16factor (CO₂ + CH₄ + NO_x) of organic soil cultivation would be between 2.9 and 10.3 Mg CO₂ ha⁻¹ y⁻¹. Maximum CO₂ production is associated with arable farming and 90-cm deep water table level. The easily mineralizable N pool makes up 0.4 to 2.8% of total N in the 0-20 cm layer, supplying 77 to 493 kg N ha⁻¹ y⁻¹ as mineral N depending on moorsh stage. Optimum volumetric air content for N mineralization is 20–30%. There is 20% more N mineralized under arable farming compared with grassland. The NO₃-N to NH₄-N ratio increases with MFP, thus enhancing N leaching and denitrification in anaerobic microsites. Addition of N-bearing fertilizers increases N pollution hazards. Organic soil quality as monitored by MFP attributes is best maintained under grassland farming with high groundwater level.