Dissolved organic matter (DOM) plays an important role in soil biological activity and transport of pollutants and nutrients in soils, but very little information is available with regard to the long-term impact of agricultural management practices on the dynamics and fate of DOM in acidic soils. The seasonal and inter-annual variation of dissolved organic carbon (DOC) and nitrogen (DON) contents and leaching were investigated in an acidic clay soil (Ferric Acrisol) by a long-term field lysimeter experiment in subtropical China. The experiment was conducted from 2002 to 2010 with 4 fertilization treatments under maize monoculture: no manure (CK), low-rate manure with 150kgNha-1y-1 (LM), high-rate manure with 600kgNha-1y-1 (HM), and high-rate manure with 600kgNha-1y-1 and lime at 3000kg Ca(OH)2ha-13y-1 (HML). Manure application resulted in a seasonal variation of soil DOC and DON, and significant effects were observed by manure DOC, microbial biomass and soil water content. Soil DOC, which was mainly determined by soil organic matter and soil water content, increased yearly until the seventh year when it was stabilized. Manure application on acidic clay soil did not alter DOC leaching, whereas DON leaching clearly increased after three years of high manure application of 600kgNha-1y-1. The average annual DON leaching losses under long-term manure application had a range of 3.8-5.4kgha-1, accounting for 6-11% of total nitrogen leached. The addition of lime, combined with manure application, produced no impact on soil dynamics and leaching of DOC and DON, with the exception of increasing emission of CO2.
