Evaluation of spatial interpolation techniques for mapping agricultural topsoil properties in Crete|
Christos G. Karydas, Ioannis Z. Gitas, Eirini Koutsogiannaki, Nikolaos Lydakis-Simantiris and Georgios N. Silleos
The aim of this work was to evaluate prediction
maps created with interpolation for five common topsoil properties, namely
organic matter, total CaCO3, electric conductivity, Fe content, and
clay content in a Mediterranean agricultural system. Knowledge about spatial
variance of soil properties is of significant importance when implementing
"good farming rules" towards sustainable rural development. A 25 ha
block of fields cultivated with grape vines and olive trees
in the island of Crete was targeted as a study site. 106 topsoil samples were collected
on a 50 × 50 m2 grid
and then analysed in the laboratory. Three well-known spatial interpolation techniques,
namely Ordinary Kriging (OK), Inverse Distance Weighting (IDW), and Radial Basis Functions
(RBF) were applied for generating
the prediction maps, which then were assessed for their accuracy and effectiveness
with a new, independent set of samples. This time the samples were collected randomly.
The results indicated that there was not a method clearly more accurate than
the other methods for any of the tested properties. The Goodness of Prediction
(G) had positive values for Fe content and total CaCO3 for all
interpolation techniques and positive values for Organic Matter only for IDW.
Among G values, only the value for total CaCO3 was big enough
for all techniques, indicating that only this specific property counted for
mapping. It is believed that the topography, crop alteration and farming
practices significantly affected the results in the specific landscape. Future
research will focus on taking account of between-field variations that are due
to different crops or farming practices, incorporating segmentation techniques
on cadastral data and satellite imagery.
Submitted: 09 Sept 2008
Revised: 19 Feb 2009
Accepted: 12 Mar 2009
Published: 31 Mar 2009
Responsible editor: Bogdan Zagajewski
Karydas C G, I Z Gitas, E Koutsogiannaki, N Lydakis-Simantiris & G N Silleos, 2009.
Evaluation of spatial interpolation techniques for mapping agricultural topsoil properties in Crete.
EARSeL eProceedings, 8(1): 26-39