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The estimation of herbage mass of perennial ryegrass swards: a comparative evaluation of a rising‐plate meter and a single‐probe capacitance meter calibrated at and above ground level
Author(s) -
MICHELL P.,
LARGE R. V.
Publication year - 1983
Publication title -
grass and forage science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.716
H-Index - 56
eISSN - 1365-2494
pISSN - 0142-5242
DOI - 10.1111/j.1365-2494.1983.tb01652.x
Subject(s) - metre , lcr meter , perennial plant , environmental science , capacitance , residual , mathematics , zoology , hydrology (agriculture) , agronomy , chemistry , geology , biology , geotechnical engineering , physics , electrode , algorithm , astronomy
Abstract A rising‐plate meter and a single‐probe capacitance meter were calibrated on perennial ryegrass swards (cultivars S23, Endura, Melle) over the spring and summer (13 March to 14 September 1981). The swards were rotationally grazed by cattle and from mid‐June onwards they were irrigated and cut at 5 cm after grazing to remove rejected herbage. Linear regressions were calculated relating meter readings to herbage dry matter mass as measured by cutting 0–2 m 2 quadrats to either 18 mm above ground or to ground level. The regression for the rising‐plate meter was constant over the spring (slope 275 kg DM ha −1 cm −1 ) and again over the summer (slope 385 kg DM ha −1 cm −1 ). The regression for the capacitance meter changed slightly over the spring (slope 11.2 to 14.0 kg DM ha −1 unit reading −1 ) and was also constant over the summer (slope 20.3 kg DM ha −1 unit reading −1 ). Correlation coefficients were always above 09 and residual standard deviations ranged from 258–525 in Spring up to 636–918 kg DM ha −1 in summer. Residual standard deviations were lower with the plate meter than with the capacitance meter and were lower with the above‐ground cutting height. Neither meter was able to give accurate results with tall rejected herbage containing a build‐up of senescent material. Herbage mass below 18 mm was greater on summer than spring swards. When compared with a ground level cut. cutting above ground underestimated herbage mass on summer relative to spring swards; there was also a tendency to underestimate herbage mass on tall pastures relative to short pastures. There was no evidence of a curved relationship between herbage mass and meter reading with either meter and both meters gave readings related to herbage dry matter mass rather than mass of green herbage or water.