The sampling method is a key aspect when designing a soil monitoring network.
The determination of any physical and chemical property can be subject to uncertainties
because of the sampling method. In this study, we compared the efficiency
of sampling with a spade and a gouge auger for the physicochemical characterization
of topsoil samples from 150 mineral soils under various land cover (LC) classes
in Switzerland taken within the LUCAS 2015 Survey. The sampling methods differed
in their scheme, accuracy of litter removal and control of sampling depth,
which were more rigorous with the gouge auger than the spade method. Values of
root mean square error of properties ranged between 1/2 and 1/30 of their mean
values. Lin's concordance correlation coefficient showed that the spade and gouge
auger methods produced similar results for all properties (LCCC ≥0.73), with a better
relation for arable land than other LC classes. A poor relation was observed for
potassium (LCCC = 0.35) in coniferous forest because of its shallow distribution in
depth. We concluded that the simpler and cheaper spade method is an accurate
method for topsoil sampling at the continental scale. From this study, it is clear that
some improvements in the control of sampling depth and the accuracy of litter
removal are needed, especially when monitoring forest soils and properties that
change rapidly with depth. Spade sampling can help to expand the implementation
of soil monitoring surveys at the continental scale at relatively low sampling cost.
Highlights
• Spade and gouge auger sampling methods were compared to monitor topsoil
properties in the LUCAS Survey.
• The gouge auger is the method of choice for properties with patchy and shallow
distribution.
• The spade method is efficient if sampling depth and litter removal are carefully
controlled.
• Spade sampling can expand topsoil monitoring at continental scale at relatively
low sampling cost.