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Spatial Modeling of a Soil Fertility Index using Visible–Near‐Infrared Spectra and Terrain Attributes
Author(s) -
Viscarra Rossel R. A.,
Rizzo R.,
Demattê J.A.M.,
Behrens T.
Publication year - 2010
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2009.0130
Subject(s) - soil water , terrain , soil fertility , environmental science , soil map , soil science , remote sensing , soil survey , digital elevation model , soil test , hydrology (agriculture) , cartography , geography , geology , geotechnical engineering
Our objective was to develop a methodology to predict soil fertility using visible–near‐infrared (vis–NIR) diffuse reflectance spectra and terrain attributes derived from a digital elevation model (DEM). Specifically, our aims were to: (i) assemble a minimum data set to develop a soil fertility index for sugarcane ( Saccharum officinarum L.) (SFI‐SC) for biofuel production in tropical soils; (ii) construct a model to predict the SFI‐SC using soil vis–NIR spectra and terrain attributes; and (iii) produce a soil fertility map for our study area and assess it by comparing it with a green vegetation index (GVI). The study area was 185 ha located in São Paulo State, Brazil. In total, 184 soil samples were collected and analyzed for a range of soil chemical and physical properties. Their vis–NIR spectra were collected from 400 to 2500 nm. The Shuttle Radar Topographic Mission 3‐arcsec (90‐m resolution) DEM of the area was used to derive 17 terrain attributes. A minimum data set of soil properties was selected to develop the SFI‐SC. The SFI‐SC consisted of three classes: Class 1, the highly fertile soils; Class 2, the fertile soils; and Class 3, the least fertile soils. It was derived heuristically with conditionals and using expert knowledge. The index was modeled with the spectra and terrain data using cross‐validated decision trees. The cross‐validation of the model correctly predicted Class 1 in 75% of cases, Class 2 in 61%, and Class 3 in 65%. A fertility map was derived for the study area and compared with a map of the GVI. Our approach offers a methodology that incorporates expert knowledge to derive the SFI‐SC and uses a versatile spectro‐spatial methodology that may be implemented for rapid and accurate determination of soil fertility and better exploration of areas suitable for production.