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Online measurement of soil organic carbon as correlated with wheat normalised difference vegetation index in a vertisol field.

Tekin Y, Ulusoy Y, Tümsavaş Z, Mouazen AM - ScientificWorldJournal (2014)

Bottom Line: Calibration model of SOC in full cross-validation resulted in a good accuracy (R (2) = 0.75, root mean squares error of prediction (RMSEP) = 0.17%, and ratio of prediction deviation (RPD) = 1.81).The validation of the calibration model using laboratory spectra provided comparatively better prediction accuracy (R (2) = 0.70, RMSEP = 0.15%, and RPD = 1.78), as compared to the online measured spectra (R (2) = 0.60, RMSEP = 0.20%, and RPD = 1.41).Although visual similarity was clear, low similarity indicated by a low Kappa value of 0.259 was observed between the online vis-NIR predicted full-point (based on all points measured in the field, e.g., 6486 points) map of SOC and NDVI map.

View Article: PubMed Central - PubMed

Affiliation: Vocational School of Technical Science, Uludag University, 16059 Bursa, Turkey.

ABSTRACT
This study explores the potential of visible and near infrared (vis-NIR) spectroscopy for online measurement of soil organic carbon (SOC). It also attempts to explore correlations and similarities between the spatial distribution of SOC and normalized differential vegetation index (NDVI) of a wheat crop. The online measurement was carried out in a clay vertisol field covering 10 ha of area in Karacabey, Bursa, Turkey. Kappa statistics were carried out between different SOC and NDVI data to investigate potential similarities. Calibration model of SOC in full cross-validation resulted in a good accuracy (R (2) = 0.75, root mean squares error of prediction (RMSEP) = 0.17%, and ratio of prediction deviation (RPD) = 1.81). The validation of the calibration model using laboratory spectra provided comparatively better prediction accuracy (R (2) = 0.70, RMSEP = 0.15%, and RPD = 1.78), as compared to the online measured spectra (R (2) = 0.60, RMSEP = 0.20%, and RPD = 1.41). Although visual similarity was clear, low similarity indicated by a low Kappa value of 0.259 was observed between the online vis-NIR predicted full-point (based on all points measured in the field, e.g., 6486 points) map of SOC and NDVI map.

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Related in: MedlinePlus

Scatter plot of predicted versus laboratory measured soil organic carbon (SOC) of the validation set (25 samples) for laboratory scanned (a) and online scanned soil spectra (b).
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fig4: Scatter plot of predicted versus laboratory measured soil organic carbon (SOC) of the validation set (25 samples) for laboratory scanned (a) and online scanned soil spectra (b).

Mentions: The performance of the vis-NIR spectroscopy for the prediction of SOC of the independent validation set under online measurement condition was not as good as that under laboratory measurement condition (Table 3). According to the classification of RPD values proposed by Viscarra-Rossel et al. [39], bother laboratory (RPD = 1.78) and online independent (RPD = 1.41) validations are classified as fair models/predictions (RPD values are between 1.4 and 1.8). Figure 4 shows the scatter plots of measured versus predicted SOC for laboratory validation and online validation. A better match of predicted versus measured SOC can be observed for the laboratory scanned spectra as compared to the online measured spectra, using the same soil samples (e.g., 25 soil samples). A relatively low model prediction performance compared to a previous report, using the same online sensor, was found as shown in Table 3 [21]. Kuang and Mouazen [21] observed clear increases in RPD values with spiked sample number per ha. On the basis of average values of the RPD of the three studied fields, authors reported that, by an increase in spiked sample number from 1/1.5 to 3.5/4.5 per ha, an average increase in RPD of 9.1% can be expected [21]. In this study about 6.5 samples per ha were spiked (67 samples for 10 ha) in the general sample set, which rejects the assumption of the effect of low number of spiked samples on resultant accuracy. Another reason for low accuracy obtained in this work might be due to the narrow variation range of the field SOC (Table 2) [21]. However, Kuang and Mouazen [21] also claimed that higher R2 and RPD for a larger variability dataset (larger range of concentration) can be obtained, but RMSEP would also be larger compared to a dataset with a small range of variability.


Online measurement of soil organic carbon as correlated with wheat normalised difference vegetation index in a vertisol field.

Tekin Y, Ulusoy Y, Tümsavaş Z, Mouazen AM - ScientificWorldJournal (2014)

Scatter plot of predicted versus laboratory measured soil organic carbon (SOC) of the validation set (25 samples) for laboratory scanned (a) and online scanned soil spectra (b).
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4109388&req=5

fig4: Scatter plot of predicted versus laboratory measured soil organic carbon (SOC) of the validation set (25 samples) for laboratory scanned (a) and online scanned soil spectra (b).
Mentions: The performance of the vis-NIR spectroscopy for the prediction of SOC of the independent validation set under online measurement condition was not as good as that under laboratory measurement condition (Table 3). According to the classification of RPD values proposed by Viscarra-Rossel et al. [39], bother laboratory (RPD = 1.78) and online independent (RPD = 1.41) validations are classified as fair models/predictions (RPD values are between 1.4 and 1.8). Figure 4 shows the scatter plots of measured versus predicted SOC for laboratory validation and online validation. A better match of predicted versus measured SOC can be observed for the laboratory scanned spectra as compared to the online measured spectra, using the same soil samples (e.g., 25 soil samples). A relatively low model prediction performance compared to a previous report, using the same online sensor, was found as shown in Table 3 [21]. Kuang and Mouazen [21] observed clear increases in RPD values with spiked sample number per ha. On the basis of average values of the RPD of the three studied fields, authors reported that, by an increase in spiked sample number from 1/1.5 to 3.5/4.5 per ha, an average increase in RPD of 9.1% can be expected [21]. In this study about 6.5 samples per ha were spiked (67 samples for 10 ha) in the general sample set, which rejects the assumption of the effect of low number of spiked samples on resultant accuracy. Another reason for low accuracy obtained in this work might be due to the narrow variation range of the field SOC (Table 2) [21]. However, Kuang and Mouazen [21] also claimed that higher R2 and RPD for a larger variability dataset (larger range of concentration) can be obtained, but RMSEP would also be larger compared to a dataset with a small range of variability.

Bottom Line: Calibration model of SOC in full cross-validation resulted in a good accuracy (R (2) = 0.75, root mean squares error of prediction (RMSEP) = 0.17%, and ratio of prediction deviation (RPD) = 1.81).The validation of the calibration model using laboratory spectra provided comparatively better prediction accuracy (R (2) = 0.70, RMSEP = 0.15%, and RPD = 1.78), as compared to the online measured spectra (R (2) = 0.60, RMSEP = 0.20%, and RPD = 1.41).Although visual similarity was clear, low similarity indicated by a low Kappa value of 0.259 was observed between the online vis-NIR predicted full-point (based on all points measured in the field, e.g., 6486 points) map of SOC and NDVI map.

View Article: PubMed Central - PubMed

Affiliation: Vocational School of Technical Science, Uludag University, 16059 Bursa, Turkey.

ABSTRACT
This study explores the potential of visible and near infrared (vis-NIR) spectroscopy for online measurement of soil organic carbon (SOC). It also attempts to explore correlations and similarities between the spatial distribution of SOC and normalized differential vegetation index (NDVI) of a wheat crop. The online measurement was carried out in a clay vertisol field covering 10 ha of area in Karacabey, Bursa, Turkey. Kappa statistics were carried out between different SOC and NDVI data to investigate potential similarities. Calibration model of SOC in full cross-validation resulted in a good accuracy (R (2) = 0.75, root mean squares error of prediction (RMSEP) = 0.17%, and ratio of prediction deviation (RPD) = 1.81). The validation of the calibration model using laboratory spectra provided comparatively better prediction accuracy (R (2) = 0.70, RMSEP = 0.15%, and RPD = 1.78), as compared to the online measured spectra (R (2) = 0.60, RMSEP = 0.20%, and RPD = 1.41). Although visual similarity was clear, low similarity indicated by a low Kappa value of 0.259 was observed between the online vis-NIR predicted full-point (based on all points measured in the field, e.g., 6486 points) map of SOC and NDVI map.

Show MeSH
Related in: MedlinePlus