Effects of oxalic acid and inhibitors on nitrogen migration rule in Karst soil
[Objective]The purpose of the study was to explore the migration law of nitrogen fertilizer with oxalic acid,nitrification inhibitor(DMPP)and urease inhibitor(NBPT)in Karst soils.The results would provide a scientific basis for the rational application of nitrogen fer-tilizer in Karst areas and improve fertilizer utilization rate.[Method]The study employed an indoor soil column culture method with a combi-nation of oxalic acid,DMPP,and NBPT,along with three nitrogen fertilizers(potassium nitrate,ammonium chloride,and urea)at 30％soil moisture.After 15,30 and 90 days cultivation,soluble inorganic nitrogen contents were determined in different soil column layers to investi-gate the effect of the nitrogen transport pattern on nitrogen fertilizer with oxalic acid and two inhibitors in Karst soils.[Result]Nitrogen fertili-zation with oxalic acid and inhibitors had obvious effect on nitrogen transport in Karst soils compared to nitrogen fertilization alone at 15,30 and 90 days cultivation times.Potassium nitrate,ammonium chloride,and urea combined with oxalic acid increased soil soluble inorganic nitrogen to 0.516,3.266,and 0.958 mg/g,respectively.The percentage of soil soluble inorganic nitrogen increased in all three nitrogen fertilizers(potassium nitrate,ammonium chloride and urea had the highest percentage of soluble inorganic nitrogen at 16.68％,41.28％and 11.02％respectively).Ammonium chloride with oxalic acid+DMPP increased the soluble inorganic nitrogen content of the soil and its per-centage increased.The highest percentage was 45.48％at 15 days of cultivation.Urea combined with oxalic acid+DMPP,resulted in the highest soluble inorganic nitrogen content and percentage in the soil after 90 days of cultivation,which were 0.935 mg/g and 11.19％,re-spectively.[Conclusion]Potassium nitrate,ammonium chloride and urea,along with oxalic acid,increased the soluble inorganic nitrogen content of the soil and promoted its transport to deeper layers in Karst areas.The content of soluble inorganic nitrogen in the soil increased in the addition of oxalic acid+DMPP to both ammonium chloride and urea.The application of this efficient use of nitrogen fertilizer applica-tion method will be employ in the agricultural production.
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