Nitrogen Inputs with Different Substrate Quality Modified pH, Eh, and N Dynamics of a Paddy Soil Incubated under Waterlogged Conditions

Synthetic fertilizer, livestock manure, and green manure are the typical nitrogen (N) sources in agriculture. This study was conducted to investigate the effects of different N sources on soil chemical environment and N dynamics. Changes in pH, redox potential (Eh), and concentration and δ¹⁵N of dissolved N [ammonium (NH₄ ⁺), nitrate (NO₃ ⁻), organic N, and total N] of soils treated with urea (U), pig manure compost (PMC), and hairy vetch (HV) were investigated in an incubation experiment under waterlogged conditions. The patterns of pH, Eh, and N concentration reflected both a greater mineralization potential of N derived from U than that from HV and PMC and easier decomposability of HV than PMC. The δ¹⁵N further suggested that nitrification was more active for U than for HV- and PMC-treated soils and that N loss via NH₃ volatilization and denitrification would be greater for HV than U and PMC treatments.