Nitrate Distribution and Accumulation in Deep Unsaturated Zone Soils in Piedmont of North China Plain

LIANG Huiya;WANG Shiqin;WEI Shoucai;Key Laboratory of Agricultural Water Resources, Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences;University of Chinese Academy of Sciences;

Deep unsaturated zone;;Nitrate;;Distribution;;Accumulation

The unsaturated zone is the link which water and nutrient transforms between atmosphere and aquifer, and it is crucial to study the distribution and accumulation of NO_3~–-N for preventing nitrate pollution in groundwater because it is the place where farmland nitrate distribute and accumulate and is the channel that nitrate leaches to the aquifer. In this study, the Geoprobe direct push system was employed to obtain 10.5 meters of continuous soil core samples from the typical deep unsaturated zones in croplands under two different fertilization(N0, no nitrogen fertilizer applied; and N600, 600 kg/(hm~2·a) nitrogen fertilizer applied in North China Plain in order to analyze the profile distribution, accumulation and key influential factors of NO_3~–-N in soils. The results showed that NO_3~–-N remained stable in N0, however, in a long-term application of 600 kg/(hm~2·a) nitrogen fertilizer(N600), NO_3~–-N leached to 10.5 m and accumulated in the deep unsaturated zone, the peak of accumulation was determined by soil texture and moisture content. The distribution and accumulation of NO_3~–-N were mainly affected by water migration, soil texture and denitrification.