01758naa a2200313 a 450000100080000000500110000800800410001910000200006024500980008026000090017852009530018765000120114065000130115265000090116565000120117465000120118665000120119865000160121065000140122665000130124065000090125365300110126265300210127365300060129465300120130070000180131270000200133077300940135016145171995-06-27       1993    bl uuuu     u00u1 u    #d1 aALVES, B. J. R.  aA rapid and sensitive flow injection technique for the analysis of ammonium in soil extracts.  c1993  aThe steam distillation technique for the quantification of soil mineral nitrogen 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/hypochlorite 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 70oC. 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 couldbe achieved. It was found that amino acids would also give a positive colorimetric reaction but that in the ten tropical soils examined this was not a significant source of error.  aammonia  anitrogen  asoil  aAmônia  aMétodo  aMineral  aNitrogênio  aNutriente  aPastagem  aSolo  aMethod  aMineral nutrient  aN  aPasture1 aBODDEY, R. M.1 aURQUIAGA, S. S.  tCommunication in Soil Science and Plant Analysis, New Yorkgv.24, n.3/4, p.277-284, 1993.