Accumulation and profile distribution of soil mineralized nitrogen in fallow season

Two long-term field experiments were conducted in the Shenyang Ecological Experimental Station, aimed to study accumulation and profile distribution of soil mineralized nitrogen (N) in upland and paddy fields with different fertilization treatments in the fallow season. Results showed that normal fertilizer application could result in accumulation and leaching loss of mineralized nitrogen (N) in the deeper layer of the soil profile in the nongrowing season in monoharvesting farmland. Accumulation of mineralized N reached the highest in the 1-m soil profile before freezing. Compared with the upland field, the accumulation amount of inorganic N in the 1-m paddy soil profile with different fertilization treatment was significantly lower. The loss profile of nitrate (NO3-)-N is observed before and after the first irrigation in spring; the first irrigation before transplanting rice seedlings in spring can cause soil nitrate leaching. Fertilization could obviously increase the accumulation and loss of NO3--N in upland and paddy fields in the fallow season, which creates the potential for groundwater nitrate pollution.