Online Measurement of Soil Organic Carbon as Correlated with Wheat Normalised Difference Vegetation Index in a Vertisol Field

Table 4

Results of Kappa test comparing symmetric measures of maps of soil organic carbon (SOC) and normalized difference vegetation index (NDVI).

Pairs	Symmetric measures		κ
	Asymp. Std. Error^a	Approx. T ^b
Laboratory measured-laboratory vis-NIR predicted SOC (25 samples)	0.004	159.722	0.473
Laboratory measured-online vis-NIR predicted SOC (25 samples)	0.004	118.344	0.367
Laboratory measured SOC (92 samples)-NDVI	0.004	71.143	0.203
Online vis-NIR predicted SOC (6486 points)-NDVI	0.004	77.392	0.259

κ: Kappa.
a: not assuming the null hypothesis.
b: using the asymptotic standard error assuming the null hypothesis.