Field-Scale Neutron Probe Calibration and Variance Analysis for Clay Soil
Publication: Journal of Irrigation and Drainage Engineering
Volume 121, Issue 5
Abstract
Although widely used for field measurements of soil moisture, problems continue with the use of the neutron probe in clay soils comprised of over 40% clay fractions, and in the determination of the intensity of field sampling necessary to characterize a site. We examine issues associated with field practice and calibration, data analysis and estimation of variance, and error in soil moisture measurements for silty clay soils in the Imperial Valley, California, using large calibration data sets from several different layouts of neutron access tubes. Our analysis indicates that for field calibrations: (1) bulk density corrections of the count ratio data do not necessarily improve the standard errors of the water content measurements; (2) soil sampling for calibration within the access tube hole at the time of tube installation results in smaller measurement errors; (3) calibrations improve as the average soil moisture of the profile at the time of the original sampling decreases; and (4) field-wide calibrations improve, and the sampling intensity required to characterize soil moisture content decreases with an increasing soil depth. We also address aspects of the neutron probe use associated with soil salinity and polyvinyl chloride (PVC) access tubing (chloride interference), inclusion of shallow sampling data in calibrations, and instrument, calibration, and spatially related standard variances affecting field measurements.
Get full access to this article
View all available purchase options and get full access to this article.
References
1.
Dickey, G. L., Allen, R. G., Barclay, J. H., Wright, J. L., Stone, J. F., and Draper, B. W. (1993). “Neutron gauge calibration, comparison of methods.”Proc., 1993 Nat. Conf. on Irrig. and Drain. Engrg., ASCE, New York, N.Y., 1136–1144.
2.
Greacen, E. L. (1981). Soil and water assessment by the neutron method . CSIRO Publication, East Melbourne, Victoria, Australia.
3.
Greacen, E. L., Correll, B. L., Cunningham, R. B., Johns, G. G., and Nicolls, K. D. (1981). “Calibration.”Soil and water assessment by the neutron method. CSIRO Publication, East Melbourne, Victoria, Australia, 50–81.
4.
Greacen, E. L., and Hignett, C. T. (1979). “Sources of bias in the field calibration of a neutron meter in cracking clay.”Australian J. Soil Res., Vol. 17, 405–415.
5.
Greacen, E. L., and Schrale, G. (1976). “The effect of bulk density on neutron meter calibration.”Australian J. Soil Res., Vol. 14, 159–169.
6.
Grismer, M. E., and Tod, I. C.(1991). “Drainage of clay overlying an artesian aquifer. I: Hydrologic assessment.”J. Irrig. and Drain. Engrg., ASCE, 117(2), 255–270.
7.
Hanson, B. R., and Dickey, G. L.(1993). “Field practices affect neutron moisture meter accuracy.”California Agr., 47(6), 29–31.
8.
Haverkamp, R., Vauclin, M., and Vachaud, G.(1984). “Error analysis in estimating soil water content from neutron probe measurements. 1: Local standpoint.”Soil Sci., 137(1), 78–90.
9.
Hewlett, J. D., Douglas, J. E., and Cutter, I. L.(1964). “Instrumental and soil moisture variance using the neutron scattering method.”Soil Sci., 97(1), 19–24.
10.
Jayawardane, N. S., Meyer, W. S., and Burns, H. D. (1983). “Moisture measurement in a swelling clay soil using neutron moisture meters.”Australian J. Soil Res., Vol. 22, 109–117.
11.
Johns, G. G., Cunningham, R. B., Durin, F. X., and Williams, J. (1981). “Site selection and representivity.”Soil and water assessment by the neutron method. CSIRO Publication, East Melbourne, Victoria, Australia, 101–116.
12.
Mitchell, A. R. (1990). “Water infiltration in a cracked soil during flood irrigation,” PhD dissertation, Dept. of Soils and Envir. Sci., Univ. of Calif., Riverside, Calif.
13.
Mitchell, A. R., and van Genuchten, M. T.(1993). “Flood irrigation of a cracked soil.”Soil Sci. Soc. Am. J., 57(2), 490–497.
14.
Nutting, P. G. (1943). “Some standard thermal dehydration curves of minerals,”USGS Profl. Paper No. 197-E, U.S. Geological Survey.
15.
Perrier, E. R., MacKenzie, A. J., and Zimmerman, R. P. (1974). “Physical and chemical properties of major Imperial Valley soils.”USDA-ARS Western Region Publ. W-17, U.S. Dept. of Agr.-Agric. Res. Service (USDA-ARS) Berkeley, Calif.
16.
Peterson, R. G., and Calvin, L. D. (1965). “Sampling.”Methods of soil analysis, C. A. Black et al. eds., Am. Soc. of Agronomy, Madison, Wis., 54–72.
17.
Sinclair, D. F., and Williams, J. (1979). “Components of variance involved in estimating soil water content and water content change using neutron moisture water.”Australian J. of Soil Res., Vol. 17, 237–247.
18.
Stone, J. F., Allen, R. G., Dickey, G. L., Wright, I. L., Nakayama, F. S., and Phillips, R. W. (1993). “The ASCE neutron probe calibration study: overview.”Proc., 1993 Nat. Conf. on Irrig. and Drain. Engrg., ASCE, New York, N.Y., 1095–1102.
19.
Tod, I. C. (1989). “Irrigation and drainage of cracking clay soil,” PhD dissertation, Dept. of Agr. Engrg., Univ. of Calif., Davis, Calif.
20.
Vandervaere, J. P., Vauclin, M., Haverkamp, R., and Cuenca, R. H. (1994a). “Error analysis in estimating soil water balance of irrigated fields during the EFEDA Experiment. 1: Local standpoint.”J. Hydrol., Vol. 56, 351–370.
21.
Vandervaere, J. P., Vauclin, M., Haverkamp, R., and Cuenca, R. H. (1994b). “Error analysis in estimating soil water balance of irrigated fields during the EFEDA Experiment. 2: Spatial standpoint.”J. Hydrol., Vol. 56, 371–388.
22.
Vauclin, M., Haverkamp, R., and Vachaud, G.(1984). “Error analysis in estimating soil water content from neutron probe measurements. 2: Spatial standpoint.”Soil Sci., 137(2), 141–148.
23.
Williams, J., and Sinclair, D. F. (1981). “Accuracy, bias and precision.”Soil and water assessment by the neutron method, CSIRO Publication, East Melbourne, Victoria, Australia, 35–49.
Information & Authors
Information
Published In
Journal of Irrigation and Drainage Engineering
Volume 121 • Issue 5 • September 1995
Pages: 354 - 362
Copyright
Copyright © 1995 American Society of Civil Engineers.
History
Published online: Sep 1, 1995
Published in print: Sep 1995
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.