High-Resolution 3-D Mapping of Soil Texture in Denmark
AUTHORS
Kabindra Adhikari
ADMIN(S)
Kabindra Adhikari
ABSTRACT
Soil texture which is spatially variable in nature, is an important soil physical
property that governs most physical, chemical, biological, and hydrological
processes in soils. Detailed information on soil texture variability both in
vertical and lateral dimensions is crucial for proper crop and land management
and environmental studies, especially in Denmark where mechanized
agriculture covers two thirds of the land area. We modeled the continuous
depth function of texture distribution from 1958 Danish soil profiles (up to
a 2-m depth) using equal-area quadratic splines and predicted clay, silt, fine
sand, and coarse sand content at six standard soil depths of GlobalSoilMap
project (0–5, 5–15, 15–30, 30–60, 60–100, and 100–200 cm) via regression
rules using the Cubist data mining tool. Seventeen environmental variables
were used as predictors and their strength of prediction was also calculated.
For example, in the prediction of silt content at 0 to 5 cm depth, factors that
registered a higher level of importance included the soil map scored (90%),
landscape types (54%), and landuse (27%), while factors with lower scores
were direct insolation (17%) and slope aspect (14%). Model validation (20%
of the data selected randomly) showed a higher prediction performance in
the upper depth intervals but increasing prediction error in the lower depth
intervals (e.g., R2 = 0.54, RMSE = 33.7 g kg−1 for silt 0–5 cm and R2 = 0.29,
RMSE = 38.8 g kg−1 from 100–200 cm). Danish soils have a high sand content
(mean values for clay, silt, fine sand, and coarse sand content for 0- to 5-cm
depth were 79, 84, 324, and 316 g kg−1, respectively). Northern parts of the
country have a higher content of fine sand compared to the rest of the study
area, whereas in the western part of the country there was little clay but a
high coarse sand content at all soil depths. The eastern and central parts of
the country are rich in clay, but due to leaching, surface soils are clay eluviated
with subsequent accumulation at lower depths. We found equal-area
quadratic splines and regression rules to be promising tools for soil profile
harmonization and spatial prediction of texture properties at national extent across
Denmark.
Department of Agroecology
Aarhus University
Blichers Alle 20, 8830 Tjele, Denmark
Soil Science Society of America, Aug. 2013, Vol 77 (3)
KEY WORDS
Digital soil mapping, Soil texture, Regression-rules, Denmark
SPAPER ID
4063
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