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The accuracy of a range of capacitance probe methods for estimating pasture yields

Published online by Cambridge University Press:  27 March 2009

G. G. Johns
Affiliation:
Department of Agronomy, University of New England, Armidale, New South Wales, 2351

Summary

Nine different capacitance probe methods were used to estimate the herbage yields of 32 small pasture plots; ten meter readings were used in conjunction with the yield data from a variable number (n) of quadrats in each plot. Expected yields were determined by cutting ten quadrats per plot. Estimated yields were compared with expected yields for both the differing methods and the differing values of n. At each level of n the yield estimates from the different probe methods were compared with those obtained simply by cutting n quadrats.

Using calibration data from only one quadrat per plot (n = 1), all probe methods except one gave greater accuracy than that obtained from the single quadrat yields only. For n = 2, the advantage of the probe methods was less pronounced and where n = 3 only one probe method (one which involved no regression computations) gave superior accuracy to that obtained merely by using the yield data from the three cut quadrats. At n > 3, only the one probe method gave increased precision; all other probe methods were markedly less accurate than the equivalent raw quadrat results.

Only one probe technique (which combined data from markedly dissimilar swards) gave yield estimates which were noticeably biased.

Results from an earlier study are presented to demonstrate the influence of season, species and irrigation on probe calibration.

Recommendations are made on the various probe methods which may prove effective in some experimental situations.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1972

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References

Alcock, M. B. (1964). An improved electronic instrument for estimation of pasture yield. Nature, Lond. 203, 1309–10.Google Scholar
Alcock, M. B. & Lovett, J. V. (1967). The electronic measurement of the yield of a growing pasture. I. Statistical assessment. J. agric. Sci., Camb. 68, 2738.CrossRefGoogle Scholar
Alder, F. E. & Richards, J. A. (1962). A note on the use of the power-driven sheep-shearing head for measuring herbage yield. J. Br. Orassld Soc. 17, 101–2.Google Scholar
Back, H. L. (1968). An evaluation of an electronic instrument for pasture yield estimation. Part 1. General relationships. J. Br. Orassld Soc. 23, 216–22.Google Scholar
Back, H. L., Alder, F. E. & Gibbs, B. G. (1969). An evaluation of an electronic instrument for pasture yield estimation. 2. Use with double sampling for regression estimation. J. Br. Orassld Soc. 24, 168–72.Google Scholar
Campbell, A. G., Phillips, D. S. M. & O'reilly, E.D. (1962). An electronic instrument for pasture yield estimation. J. Br. Orassld Soc. 17, 89100.CrossRefGoogle Scholar
Dowling, E. J., Spencer, K. & Bouma, D. (1966). The performance of a capacitance-measuring instrument in estimating yield of subterranean clover pastures. Fid Stn Rec. Div. PI. Ind. C.S.I.R.O. (Ausi.) 4, 103–7.Google Scholar
Fletcher, J. E. & Robinson, M. E. (1956). A capacitance meter for estimating forage weight. J. Range Mgmt 9, 96–7.CrossRefGoogle Scholar
Hyde, F. J. & Lawrence, J. T. (1964). Electronic assessment of pasture growth. Electronic Engng, 36, 666–70.Google Scholar
Johns, G. G. (1971). Water use efficiency in dryland herbage production. Ph.D. thesis, Univ. New England, N.S.W., pp. 238.Google Scholar
Johns, G. G., Nicol, G. R. & Watkin, B. R. (1965). A modified capacitance probe technique for estimating pasture yield. I. Construction and procedure for use in the field. J. Br. Orassld Soc. 20, 212–17.Google Scholar
Johns, G. G. & Watkin, B. R. (1965). A modified capacitance probe technique for estimating pasture yield. II. The effect of different pastures, soil types and dew on the calibration. J. Br. Orassld Soc. 20, 217–26.CrossRefGoogle Scholar
Jones, R. J. & Haydock, K. P. (1970). Yield estimation of tropical and temperate pasture species using an electronic capacitance meter. J. agric. Sci., Camb. 75, 2736.CrossRefGoogle Scholar
Lovett, J. V. (1966). A comparison of pasture productivity in hill and lowland environments. Ph.D. thesis, Univ. Wales, pp. 168.Google Scholar
Neal, D. L. & Neal, L. R. (1965). A new electronic meter for measuring herbage yield. U.S. Forest Service Research Note P.S.W. 56, 14.Google Scholar
Van Dyne, G. M., Glass, F. M. & Opstrup, P. A. (1968). Development and use of capacitance meters to measure standing crop of herbaceous vegetation. Oak Ridge National Laboratory Report ORNL-TM- 2247, pp. 47.Google Scholar