Comparison of Nitrate and Ammonium Leaching of Soils Collected from Different Regions of China: A Soil Column Experiment

Soil nitrogen (N) leaching varies substantially in amounts and rates depending on soil type and N form, but the underlying mechanisms for this variation are largely unknown. We used six soils collected from the south, east, central, and west regions of China to examine the leaching of nitrate and ammonium in these soils through a soil column experiment during eight days. Large amounts of nitrate were leached in the starting three days, but only small amounts of ammonium were leached during the eight days. After eight-day leaching, most of applied ammonium was retained in soils, but nitrate residue in soils was very low. The cumulative nitrate leaching amounts were ordered as follows: the two acid soils from South China > the two neutral soils from South and East China > the two alkaline soils from Central and West China. The neutral and alkaline soils had fewer clay, more sand and organic matter, and higher denitrification potential compared with the acid soils. Nitrate leaching amount was negatively correlated with denitrification potential in different soils, suggesting that fewer nitrate leaching and residual in the neutral and alkaline soils may be attributed to their stronger denitrification relative to the acid soils. Nitrate is rapidly lost through leaching in the present acid soils and through denitrification in the neutral and alkaline soils, whereas ammonium is mostly remained in all soils with little leaching. Soil denitrification potential may be responsible for the difference in nitrate leaching among the six soils.

Automated summary

Leaching of nitrate and ammonium in soil varies with soil type and N form. Acidic soils have higher nitrate leaching, while neutral and alkaline soils have lower nitrate leaching due to their stronger denitrification potential. Ammonium is mainly retained in all soils with little leaching.