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Use of on-ground gamma-ray spectrometry to measure plant-available potassium and other topsoil attributes
Journal article   Peer reviewed

Use of on-ground gamma-ray spectrometry to measure plant-available potassium and other topsoil attributes

M.T.F. Wong and R.J. Harper
Australian Journal of Soil Research, Vol.37(2), pp.267-278
1999
DOI: https://doi.org/10.1071/S98038
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Abstract

The incidence of potassium (K) deficiency is increasing in crops, pastures, and forestry in south-western Australia. Although soil K can be measured using soil sampling and analysis, γ-ray spectrometry offers a potentially cheaper and spatially more precise alternative. This could be particularly useful in precision agriculture, where inputs are applied according to need rather than by general prescription. In a study of topsoils near Jerramungup, Western Australia, strong relationships (r2 = 0·9) were found between on-ground counts of γ-rays derived from 40K (γ-K) and both total K and plant-available K. The success of γ-ray spectrometry in predicting available K relied on a strong relationship (r2 = 0·9) between total K and available K which may not hold in all areas. Although the relationship between γ-K and available K held over the range of 36–1012 mg/kg, crop response to K fertilisers is only expected when the available K content is <100 mg/kg. Estimates of available K from γ-K were unreliable at this lower end of the regression curve. Separate analysis with a subset of the data with available K <100 mg/kg showed a poor relationship between γ-K and available K (r2 = 0·05; d.f. 11). The usefulness of γ-ray spectrometry may therefore be restricted to defining areas where response to fertiliser K may occur, and where further soil sampling and analysis are required to predict the fertiliser requirement. Strong relationships (r2 = 0·9) were also found between γ-K and a range of other soil attributes, including clay, silt, and organic carbon content. These relationships depended on the locally strong relationship between total K and these soil attributes. Since such relationships do not hold everywhere, the utility of γ-ray spectrometry will likewise be limited. Site-specific calibrations are required if γ-ray spectrometry is to be used for soil property mapping.

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Source: InCites

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94 Record Views
75 Times Cited - Web of Science

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Citation topics
3 Agriculture, Environment & Ecology
3.45 Soil Science
3.45.1109 Soil Mapping
Web Of Science research areas
Soil Science
ESI research areas
Environment/Ecology
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