Near infrared reflectance spectroscopy for the analysis of agricultural soils

The objective of this work was to investigate the usefulness of near infrar ed (NIR) reflectance spectroscopy in determining: (i) various constituents (total N, total C, active N, biomass and mineralisable N, and pH), (ii) par ameters (soil source, depth from which sample was obtained, type of tillage used) and (iii) rate of application of NH4NO3 fertiliser) of low organic m atter soils. A NIRSystems model 6250 spectrometer was used to scan soil sam ples (n = 179) obtained from experimental plots at two locations with three replicate plots under plow and no till practices at each location with thr ee rates of NH4NO3 for each plot (2 x 3 x 2 x 3). For each of these, sample s were taken from five depths for a total of 2 x 3 x 2 x 3 x 5 or 180 sampl es (one sample lost). The results demonstrated that NIR reflectance spectro scopy can be successfully used to determine some compositional parameters o f low organic matter soils (particularly total C and total N). It is also a pparent that for non-biological parameters (excluding soil type as reflecte d by source) such as the depth from which the sample was obtained, the rate of application of NH4NO3 fertiliser and the form of tillage used, that NIR reflectance spectroscopy is not very useful, unless a very limited set of samples is used (i.e. single tillage and location). For other determination s, such as pH, biomass N and active N, the results may be useful depending on the exact needs in question. Finally, from the results presented here, N IR reflectance spectroscopy was not successful in determining soil N minera lisable in 21 days.