Abstract form

The effect of changing sampling strategy on salt-affected soil profile
data evaluation
Zsófia BAKACSI*, Tibor TÓTH
Research Institute for Soil Science and Agricultural Chemistry of the Hungarian
Academy of Sciences
*Corresponding author’s e-mail: zsofi@rissac.hu
The Hungarian Soil Monitoring system has been in existence since 1992, and
characterizes 1236 soil sampling sites, representing different land use categories. From
the beginning till 2000, concerning the Hungarian genetic soil classification system, the
applied systematic sampling focused on the genetic soil horizons. This sampling
strategy fully accepted the genetic based soil stratification, and each sample represented
a genetic soil horizon. The resulted profile-data were available for detecting the changes
in soil properties, but the claim to spatial correlation and international harmonization
called for a new concept of sampling. According to the new method the sampling area
enlarged, and focused not only the profile, but for a 50 m circle around the profile. The
average samples are collected from nine boreholes, equidistantly in 0-30 cm, 30-60 cm
and 60-90 cm depth intervals. In the year of the changes, because of the comparability
and continuity, all the profiles were sampled with both of the methods (by horizons and
equidistantly). This paper focuses on the effect of the methodological change for the
salt-affected soil profile data evaluation in a dataset for the period 1992-2003.
Assumed that the characteristic salt profile was well described with the genetic soil data
set, we studied whether the new dataset originating from the equidistant sampling shows
the same salt profile or not. We divided the salt content data of the upper three soil
horizons in 10 groups, according to the genetic types and/or subtypes of salt affected
soils -determined in the Hungarian Soil Monitoring system- and compared the measured
salt content data according to their sampling strategy. In the genetic based dataset the
three horizons are separated sharply, and -with few exceptions- the lowest salt content
occurs in the surface-subsurface layer and the salt content increases with the depth. In
the equidistant based dataset the separated horizons “moved” closer to each other, the
difference between the salt content of the layers decreased. In some cases the earlier
order of salt content changed and the second and third layer has the same salt content
value. Using the equidistant method, as a result of the overlapping sampling, the effect
of the salt-content changes in the genetic soil horizons is less clear.
In each soil type or subtype that we analysed the differences between the two groups of
dataset by the Kruskal-Wallis test, and in some cases the expectation for the continuity
of the 1992-2003 dataset seems not to be fulfilled.
Key words: sampling strategy, salt-affected soils
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