01656naa a2200265 a 450000100080000000500110000800800410001910000200006024500980008026000090017852009540018765000130114165000140115465000090116865000130117765000160119065000150120665000090122165300130123065300110124365300130125470000180126770000200128577300850130517903242017-04-03       1993    bl ---       0--  u    #d1 aALVES, B. J. R.  aA rapid and sensitive flow injection technique for the analysis of ammonium in soil extracts.  c1993  aThe steam distilation technique for the quantification of soil mineral nitrogens is not well adapted to estimate very low levels of NH4+ and NO3- such as those found in tropical pastures. In this paper we describe a flow injection analysis (FIA) technique for the direct estimation of soil ammonium in potassium chloride extracts. The technique is based on the salicylate/hypochloride colorimetric reaction with the resulting colouration read at 647 nm. The speed of the reaction was increased by immersing the reaction coils in a water bath maintained at 70C. The technique was capable of accurately quantifying ammonium to concentrations as low as 0.05 mg NH4+-N/L (equivalent to 0.25 mg NH4+-N/g dry soil) and sample thoughputs of at least 60 samples per hour could be achieved. It was found that amino acids whould also give a positive colorimetric reaction but that in the ten tropical soils examined this was not a significant source of error.  anitrogen  anutrition  asoil  aAnálise  aNitrogênio  aNutrição  aSolo  aAmmonium  aAmonio  aAnalysis1 aBODDEY, R. M.1 aURQUIAGA, S. S.  tCommunications in Soil Science and Plant Analysisgv.24, n.3/4, p.277-284, 1993.