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Value of a rising‐plate meter for estimating herbage mass of grazed perennial ryegrass‐white clover swards
Author(s) -
MICHELL P.
Publication year - 1982
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.1365-2494.1982.tb01580.x
Subject(s) - perennial plant , linear regression , calibration , quadrat , regression analysis , mathematics , agronomy , environmental science , dry matter , grazing , statistics , biology , ecology , shrub
A rising‐plate meter was used in a double sampling technique to measure the herbage mass of rotationally grazed perennial ryegrass‐white clover swards over a period of 2 years. The meter was calibrated by developing a linear regression between meter reading and herbage dry matter mass as measured by cutting 0·2‐m 2 quadrats to ground level. There was a strong relationship between meter reading and herbage mass, and correlation coefficients were consistently 0·2 or above. The calibration regression was normally constant for extended periods, especially over the winter and spring. The relationship was more variable over the summer but appeared to follow a pattern that was to some extent repeatable between years. The slope of the regression (kg DM ha ‐1 cm ‐1 ) was 312 and 267 in the two winters and reached values of 800 and 452 in the two summers. The calibration relationship was adequately described by a linear model over the winter and spring but there was a tendency for a curved relationship in mid‐to late summer. The standard pooled regression found with winter ryegrass‐clover swards was not applicable to the more erect prairie grass, and the standard regression overestimated slightly the yield of heavily grazed swards. There was no evidence of a difference in relationship between irrigated and non‐irrigated swards over the summer. The individual meter readings could be used to develop a useful diagrammatic picture of the changes that occurred in sward structure as the pastures were subjected to different managements and this could be used to illustrate problem areas in pasture management. The meter was useful in overcoming the problem of variability of herbage mass within paddocks and could give precise estimates of herbage mass, especially when it was possible to use a pooled regression encompassing a large number of calibration cuts. In these cases the meter could be used to detect differences of about 8%.