Consequences of soil sampling depth during the assessment of the effects of tillage and fertilization on soil quality: a common oversight

The objective of this work is to discuss the consequences of soil sampling depth during the assessment of the effects of tillage and fertilization on soil quality, within the context of a well-known recommendation: the imperative need to consider soil depths covering the entire plow layer during such assessment. It is necessary to (i) warn that this recommendation is most often forgotten and (ii) illustrate with real data the consequences of this common oversight. We carried out two field experiments in Derio (Spain): the first (2004) on a Dystric Cambisol and the second (2005-2007) on an Epidystric Cambisol. We hypothesized that conflicting conclusions regarding the effects of tillage and fertilization on soil quality can be drawn depending on the soil depth subjected to analysis. With respect to soil enzymes, it was found that inconsistencies in values with soil depth can be reduced when the results are expressed as specific activities.