Effects of Subsetting by Carbon Content, Soil Order, and Spectral Classification on Prediction of Soil Total Carbon with Diffuse Reflectance Spectroscopy

Table 1

Soil properties of selected samples for each soil grouping used in subsetting by soil order. Values listed in the table are the minimum and maximum for that specific subset with the mean in parentheses. Data is provided for samples from the Natural Resources Conservation Service (NRCS) archive where it is available. The compositional information (i.e., pH, texture, Al, Ca, and Fe) for the samples newly collected in 2010 has yet to be determined.

	Total carbon wt%	Organic carbon wt%	Clay wt%	Silt wt%	Sand wt%	pH	Total Al wt%	Total Ca wt%	Total Fe wt%
Andisol; soils	0.24–51	0.39–55.59	0.3–59.8	4.7–81.3	2.4–94.9	3.7–8	1.58–13.89	0.025–4.80	7.33–22.63
	(13.39)	(12.53)	(17.26)	(40.62)	(42.83)	(5.66)	(8.54)	(0.64)	(15.49)
High activity clay soils	0.21–53.63	0.3–14.65	0.2–66.7	10.8–93.2	0.4–88.6	3.3–8.3	10.95^a	0.52^a	10.13^a
	(14.51)	(3.94)	(25.72)	(44.08)	(30.21)	(5.89)
Low activity clay soils	0.15–10	0.2–3.58	7.6–88.7	10.4–69.5	0.75–69.8	4.5–7.3	7.66–9.61	0.049–0.16	13.43–27.03
	(1.65)	(1.11)	(47.52)	(34.86)	(17.61)	(5.92)	(8.28)	(0.096)	(23.23)
Organic-dominated soils	5–55.29	2.62–54.98	4.4–67.6	11.5–45.7	1.3–84.1	3.3–5.8		Not available
	(36.19)	(20.26)	(31.68)	(30.45)	(37.86)	(4.29)

^aOnly one data point available.