TY - JOUR

T1 - Incorporating a periodic function into an equation for estimating herbage mass in Zoysia-dominated pastures from rising plate readings

AU - Itano, Shiro

AU - Tomimatsu, Hajime

AU - Nakagami, Koji

AU - Maeda, Yasuyuki

PY - 2012/9

Y1 - 2012/9

N2 - A rising plate meter (RPM), which enables rapid, non-destructive estimation of herbage mass of pastures, is useful in grazing management. Herbage mass is estimated from the RPM readings using a linear regression model, which has the parameters α (constant) and β (slope). In this study, we analyzed the seasonal changes in the two parameter values for total and green herbage (TH and GH, respectively) masses in Zoysia-dominated pastures, and examined the potential for incorporating a periodic function (PF) of the parameters into the equation for estimating herbage mass. The values of both α and β showed a weak seasonal periodicity for TH. No periodicity and a clear seasonal periodicity were detected in the α and β values for GH, respectively. Compared with the linear regression models developed separately for individual dates, the equation incorporating a PF for β improved the estimation accuracy for the GH mass (from 0.64 to 0.77 as R2), though it did not affect the predictability for the TH mass. Incorporation of a PF into the model relating herbage mass to the RPM reading increases the sample number and broadens the data range by allowing the use of all seasonal data, and produces a single equation useful for estimating herbage mass across seasons.

AB - A rising plate meter (RPM), which enables rapid, non-destructive estimation of herbage mass of pastures, is useful in grazing management. Herbage mass is estimated from the RPM readings using a linear regression model, which has the parameters α (constant) and β (slope). In this study, we analyzed the seasonal changes in the two parameter values for total and green herbage (TH and GH, respectively) masses in Zoysia-dominated pastures, and examined the potential for incorporating a periodic function (PF) of the parameters into the equation for estimating herbage mass. The values of both α and β showed a weak seasonal periodicity for TH. No periodicity and a clear seasonal periodicity were detected in the α and β values for GH, respectively. Compared with the linear regression models developed separately for individual dates, the equation incorporating a PF for β improved the estimation accuracy for the GH mass (from 0.64 to 0.77 as R2), though it did not affect the predictability for the TH mass. Incorporation of a PF into the model relating herbage mass to the RPM reading increases the sample number and broadens the data range by allowing the use of all seasonal data, and produces a single equation useful for estimating herbage mass across seasons.

KW - Green mass

KW - Herbage mass

KW - Periodic function model

KW - Rising plate meter

KW - Zoysia-dominated pastures

UR - http://www.scopus.com/inward/record.url?scp=84865653637&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84865653637&partnerID=8YFLogxK

U2 - 10.1111/j.1744-697X.2012.00253.x

DO - 10.1111/j.1744-697X.2012.00253.x

M3 - Article

AN - SCOPUS:84865653637

SN - 1744-6961

VL - 58

SP - 127

EP - 132

JO - Grassland Science

JF - Grassland Science

IS - 3

ER -