engleski

Analytical chemistry in service of nitrogen determination and protection of soil and water

Nitrogen (N) is one of seventeen essential elements required for optimal plant growth and development. Plants receive an N in mineral form (NO3- and NH4+) which exist in soil in insufficient quantities so nitrogen fertilization today is an indispensable measure in agricultural production. Many scientific studies indicate that excessive N fertilization is a threat to the environment so the crucial step in environment protection is development of analytical methods which will quickly and reliably quantify N in soil. The above refers primarily to the methods for nitrates detection because they do not bind to the soil adsorption complexes and end in groundwater or surface water. The primary objective of this paper was to compare three analytical methods for nitrates determination in soil with respect to the applied extraction agents, the selectivity and the speed of analysis. The study was conducted on 60 soil samples collected from a field trial which involves long-term N fertilization in the range from 0 to 300 kg/ha. The results reveal that diverse extraction agents (0.2 M K2SO4 and ultra pure water) extracted a significantly different content of nitrate nitrogen from the soil. The average extracted content decreased by the following sequence of analytical methods: spectrophotometry (9.88 mgN-NO3/kg) > ion selective potentiometry (3.69 mgN-NO3/kg) > ion chromatography (3.10 mgN-NO3/kg). Significant influence of chloride ions was determined on the selectivity of the nitrate electrode during potentiometric measurement. The spectrophotometric method involves evaporation of soil extract which further extends the time of analysis.

environment ; nitrates ; spectrophotometry ; ion selective potentiometry ; ion chromatography

nije evidentirano