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Increased sample point density in farm soil mapping by local calibration of visible and near infrared prediction models

Wetterlind, Johanna and Stenberg, Bo and Söderström, Mats (2010). Increased sample point density in farm soil mapping by local calibration of visible and near infrared prediction models. Geoderma. 156:3-4, 152-160
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Official URL: http://dx.doi.org/ 10.1016/j.geoderma.2010.02.012

Abstract

For use as decision support for variable rate applications in precision agriculture, the commonly used sample point density of one sample per hectare is often not enough. However, increasing the sampling density using laboratory analyses is too expensive for farmers to implement. It is there-fore important to find methods for rationalisation. To this end, farm-scale visible and near infrared reflection (vis–NIR) calibrations were established on two farms in southern Sweden (Hacksta and Sjöstorp) for soil texture, soil organic matter, total N, pH and plant-available P, K and Mg. By keeping the laboratory analyses to a minimum to be used for vis–NIR calibrations and only collect-ing vis–NIR spectra from the vast majority of the samples, the sampling density could be increased without significantly increasing the cost. In this study 25 samples were used in the calibrations. Six different calibration sample selection methods were compared, selected from three different data-sets originating from a larger context aiming at covering soil variations. Using only 25 calibration samples resulted in good predictions for clay at both farms, r2 values of 0.81 and 0.89 and RMSEP
values of 3.6 and 3.9%. Sand, soil organic matter and total nitrogen were well predicted at Hacksta (r2=0.87, 0.90 and 0.89 and RMSEP=3.0, 0.28 and 0.018% respectively) but 25 samples proved to be too few at the geologically divided farm Sjöstorp. For predicting pH and plant-available P, K and Mg, more than 25 calibration samples were needed at both farms, although with 75% of all ref-erence samples (92 and 94 at Hacksta and Sjöstorp respectively) in the calibration these parameters also showed potential for building useful NIR calibrations (RPD values between 2.3 and 2.8 except for the predictions for pH at one of the farms resulting in an RPD value of 1.6). However, predic-tions for silt content were less reliable and the small number of calibration samples was not the li-miting factor in this case. The promising results are encouraging for further development of cost-effective high resolution farm soil maps using NIR spectroscopy.

Authors/Creators:Wetterlind, Johanna and Stenberg, Bo and Söderström, Mats
Title:Increased sample point density in farm soil mapping by local calibration of visible and near infrared prediction models
Series/Journal:Geoderma (0016-7061)
Year of publishing :2010
Volume:156
Number:3-4
Page range:152-160
Publisher:Elsevier
ISSN:0016-7061
Language:English
Publication Type:Journal article
Refereed:Yes
Article category:Scientific peer reviewed
Version:Accepted version
Full Text Status:Public
Agris subject categories.:F Plant production > F04 Fertilizing
P Natural resources > P30 Soil science and management
P Natural resources > P31 Soil surveys and mapping
Subjects:(A) Swedish standard research categories 2011 > 2 Engineering and Technology > 207 Environmental Engineering > Remote Sensing
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Agricultural Science
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Soil Science
Keywords:Diffuse reflectance spectroscopy, Plant-available P, K and Mg, Soil pH, Precision agri-culture, Clay, Soil organic matter
URN:NBN:urn:nbn:se:slu:epsilon-e-909
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-909
ID Code:9494
Department:(NL, NJ) > Dept. of Soil and Environment
(S) > Dept. of Soil and Environment
External funders:Stiftelsen Lantbruksforskning
Deposited By: J Wetterlind
Deposited On:14 Mar 2013 09:10
Metadata Last Modified:31 Mar 2015 12:08

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