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Combining two national-scale data sets to map soil properties, the case of available magnesium in England and Wales: combining two soil surveys

Lark, R. M.; Ander, E. L.; Broadley, M. R.

Authors

MURRAY LARK MURRAY.LARK@NOTTINGHAM.AC.UK
Professor of Geoinformatics

E. L. Ander



Abstract

Given the costs of soil survey it is necessary to make the best use of available data sets, but data which differ with respect to some aspect of the sampling or analytical protocol cannot be combined simply. In this paper we consider a case where two data sets were available on the concentration of plant‐available magnesium in the topsoil. The data sets were the Representative Soil Sampling Scheme (RSSS) and the National Soil Inventory (NSI) of England and Wales. The variable was measured over the same depth interval and with the same laboratory method, but the sample supports were different and so the data sets differ in their variance. We used a multivariate geostatistical model, the linear model of coregionalization (LMCR), to model the joint spatial distribution of the two data sets. The model allowed us to elucidate the effects of the sample support on the two data sets, and to show that there was a strong correlation between the underlying variables. The LMCR allowed us to make spatial predictions of the variable on the RSSS support by cokriging the RSSS data with the NSI data. We used cross‐validation to test the validity of the LMCR and showed how incorporating the NSI data restricted the range of prediction error variances relative to univariate ordinary kriging predictions from the RSSS data alone. The standardized squared prediction errors were computed and the coverage of prediction intervals (i.e. the proportion of sites at which the prediction interval included the observed value of the variable). Both these statistics suggested that the prediction error variances were consistent for the cokriging predictions but not for the ordinary kriging predictions from the simple combination of the RSSS and NSI data, which might be proposed on the basis of their very similar mean values. The LMCR is therefore proposed as a general tool for the combined analysis of different data sets on soil properties.

Journal Article Type Article
Publication Date Oct 5, 2018
Journal European Journal of Soil Science
Print ISSN 1351-0754
Electronic ISSN 1365-2389
Publisher Wiley
Peer Reviewed Peer Reviewed
APA6 Citation Lark, R. M., Ander, E. L., & Broadley, M. R. (2018). Combining two national-scale data sets to map soil properties, the case of available magnesium in England and Wales: combining two soil surveys. European Journal of Soil Science, https://doi.org/10.1111/ejss.12743
DOI https://doi.org/10.1111/ejss.12743
Keywords Soil Science
Publisher URL https://onlinelibrary.wiley.com/doi/abs/10.1111/ejss.12743

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