Effects Of Acidification And Freeze-thaw On Ammonia Migration Activity In Black Soil

Due to the rapid population growth and the rapid industrial development in recent years,people one-sided pursuit of GDP growth blindly, the soil is facing "serious overdraft". TheAcidification causes the decline of soil’s fertility, thus it brings compaction and degradationoccurs, and it also diminishes the yield and quality of crop at last. As the essential nutrients ofcrop, the nitrogen is very close relationship with the yield and quality of crops. However, thelow utilization of nitrogen cause economic losses, but also cause severe environmental problems.So it is very necessary to make a thorough inquiry the adsorption characteristics and verticalmigration of nitrogen which is in the acidification for improving the utilization of nitrogen andreducing environmental pollution. The ammonia of soil was selected as a indicator to discussedthe effects of soil acidification on nitrogen adsorption characteristics and variation of verticalmigration under different experimental conditions. the research has the following conclusions:(1) This study aimed to investigate the characteristic of ammonia absorption in control soilsand acidified soils by the methods of adopting equilibrium adsorption and Nesslerspectrophotometric. The results showed that, the ammonia absorption in acidified soils andcontrol soils experienced rapid adsorption, slow adsorption equilibrium sorption.The amount ofequilibrium adsorption in control soils and acidified soils were1324mg/kg and1194mg/kg. Thelow temperatures had function to enhance the soil’s capability of ammonia absorption, and theaffects of mutative temperature on ammonia absorption of acidified soil was more sensitive thanthe control soil. the ammonia adsorption capacity of two soil increased with the increasing ofammonia solution pH, and the amount of equilibrium adsorption in acidified soils was moresusceptible to outside influence on the change of pH. After the removal of organic matter in twogroups of soil, the ammonia adsorption capacity of acidified soil was lower than the control soil,acidification could diminished the ammonia adsorption capacity of the soil organic matter.Results showed that the ammonia adsorption capacity reduced with the increasing offreeze-thaw cycles, it showed a trend which was from increase to decreasing about thedifferences of ammonia adsorption capacity in two groups of soil. The biggest difference of soiladsorption came in the fifth weeks’free-thaw cycles; when the freeze-thaw cycles increased to8cycles, two adsorption curve almost coincidence, it indicated the impact of free-thawing onammonia adsorption minimize after8weeks’free-thaw cycles. it had no significant changesunder the different freeze times; it reduced with the increasing of moisture contentbefore-freezing, the adsorption capacity of ammonia in different moisture before-freezing treatments soil were arranged by descending order as follows:15%>25%>35%. Langmuirisotherms was fitted to the adsorbed ammonium in the solution using regression procedure, itgave good fits of the measured data. Acidification promoted the release of ammonia andincreased soil ammonia loss risk.(2) This study aimed to investigate the variation of vertical migration in control soils andacidified soils by the methods of soil-column leaching. The results showed that: the ammoniacontent in leachates of two groups’ soil were shown the trend which was from increase to fallthen tended to balance; the ammonia content of leaching liquid decreased with the increasing ofpH. The soil organic matter content of soil had inhibition function of the vertical migration ofammonia, the ammonia content of leaching liquid decreased in soil which had high organicmatter content.With the increase of freeze-thaw cycles, the cumulative amount of ammonialeaching solution presented rise firstly after fall and then trended leveled off at last, the effectswhich freeze-thaw cycles could increased the ammonia content of leaching liquid in acidifiedsoil was more obvious than control soils. When the freeze-thaw cycles increased to3cycles, theammonia content of leaching liquid in acidified soil reached a max to179.1mg/L, when thefreeze-thaw cycles increased to5cycles, the ammonia content of leaching liquid in control soilreached a max to106.1mg/L; With the increase of freezing time, the cumulative amount ofammonia leaching solution increased gradually. The amount of ammonia leaching liquiddecreased gradually with the increase of moisture content before-freezing; the content of liquidin Acidified soil were higher than the control soil under the same conditions. Freeze-thawprocess promoted the release of acidified soil ammonium and increased soil ammonia loss risk.Acidification promoted the release of ammonia under the process of freeze-thaw and increasedsoil ammonia loss risk under freezing-thaw action.