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Purpose <p>Rising plate meters (RPM) can provide a quick and low-cost approach to measure and monitor changes in pasture herbage mass. Calibration equations for modern diverse swards are needed. Herbage mass prediction equations for use with a RPM in modern diverse swards were developed.</p> Method <p>A total of 2,247 fresh herbage samples were collected between the years 2017 and 2024 from 148 different land parcels in the UK that were either managed for grazing and/or conservation or not managed for agricultural use. The swards had a range of grass and non-grass species, with temporary grass and permanent grass areas consisting of 95% grass species compared to 67% grass content for more diverse temporary swards. The herbage properties of compressed sward height (measured by RPM in centimeters), dry matter (DM) content (g/kg), fresh weight (FW) and DM herbage mass (both kg/ha), fresh and DM densities (both kg/ha/cm) were measured and used to develop herbage mass prediction equations for use with a RPM. Fresh weight and DM cover measurements were used to develop prediction equations.</p> Results <p>Prediction errors of derived linear equations for FW and DM herbage mass were mainly associated with random error (proportion of MSPE &gt; 0.5), rather than overall mean bias or slope bias, with overall error lowest for managed temporary grass areas (RMSPE = 2902 and 2867 FW kg/ha, and 590 and 575 DM kg/ha, for intercept and herbage density or solely herbage density predictions, respectively). Correlations between observed and predicted FW and DM herbage mass, based on linear intercept and herbage density or solely herbage density per sward height, for managed temporary grass and diverse swards were higher (<i>r</i> &gt; 0.49) than unmanaged or permanent grass swards (<i>r</i> &lt; 0.40).</p> Conclusion <p>In managed swards, herbage mass predictions can be made based solely on herbage density × compressed sward height using the derived density coefficients, whereas accounting for the linear intercept was more important in unmanaged swards. Calibration equations to estimate FW and DM herbage mass based on compressed sward height with a RPM were found to be more suited for use with managed swards, rather than unmanaged swards with a large intercept value or with a greater diversity of species.</p>

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Calibrating a rising plate meter to predict herbage mass of modern diverse agricultural swards

  • 期刊论文

  • 发表日期：

    2026年6月27日

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  • Matt J. Bell,
  • Tim Bevan,
  • Brian Evans,
  • Wing Ng,
  • Felicity Roos

摘要

Purpose

Rising plate meters (RPM) can provide a quick and low-cost approach to measure and monitor changes in pasture herbage mass. Calibration equations for modern diverse swards are needed. Herbage mass prediction equations for use with a RPM in modern diverse swards were developed.

Method

A total of 2,247 fresh herbage samples were collected between the years 2017 and 2024 from 148 different land parcels in the UK that were either managed for grazing and/or conservation or not managed for agricultural use. The swards had a range of grass and non-grass species, with temporary grass and permanent grass areas consisting of 95% grass species compared to 67% grass content for more diverse temporary swards. The herbage properties of compressed sward height (measured by RPM in centimeters), dry matter (DM) content (g/kg), fresh weight (FW) and DM herbage mass (both kg/ha), fresh and DM densities (both kg/ha/cm) were measured and used to develop herbage mass prediction equations for use with a RPM. Fresh weight and DM cover measurements were used to develop prediction equations.

Results

Prediction errors of derived linear equations for FW and DM herbage mass were mainly associated with random error (proportion of MSPE > 0.5), rather than overall mean bias or slope bias, with overall error lowest for managed temporary grass areas (RMSPE = 2902 and 2867 FW kg/ha, and 590 and 575 DM kg/ha, for intercept and herbage density or solely herbage density predictions, respectively). Correlations between observed and predicted FW and DM herbage mass, based on linear intercept and herbage density or solely herbage density per sward height, for managed temporary grass and diverse swards were higher (r > 0.49) than unmanaged or permanent grass swards (r < 0.40).

Conclusion

In managed swards, herbage mass predictions can be made based solely on herbage density × compressed sward height using the derived density coefficients, whereas accounting for the linear intercept was more important in unmanaged swards. Calibration equations to estimate FW and DM herbage mass based on compressed sward height with a RPM were found to be more suited for use with managed swards, rather than unmanaged swards with a large intercept value or with a greater diversity of species.