Accurate estimation of herbage mass (HM) is essential for optimising grass utilisation and increasing profit for pasture-based livestock agriculture. The rising plate meter (RPM) is used for predicting HM based on average compressed sward height (CSH). Sampling resolution and distribution are primary parameters in determining spatial heterogeneity of HM. There is no definitive sampling protocol for the RPM. The objectives of this study were to: investigate spatial variation of HM within pastures, determine the number of RPM measurements required to accurately predict mean HM, and assess the precision of the RPM in terms of measurement repeatability. Intensive CSH measurements and HM reference cuts were carried out on controlled plots and grazed paddocks over two grazing seasons. Sward heterogeneity was estimated as the coefficient of variation (CV) of CSH and compared to empirically derived ‘true’ sward heterogeneity in terms of HM CV. Retrospective analysis simulations were performed to identify the effect of various reduced measurement resolutions on estimated mean CSH error. Repeated measures analysis was performed on grass samples to determine RPM measurement system precision. Results indicated that pasture heterogeneity varied by 36% across the growing season and was affected by grazing, fertilisation, sward composition and seasonality. Mean CSH could be estimated to within 5% relative prediction error by recording 24 measurements per ha in a random stratified manner. The standard deviation of RPM measurement repeatability was calculated to be 4.34 mm. The findings of this study will be used to inform the implementation of a more optimum grass measurement protocol.

中文翻译：

---

升板仪测量异质草原草丛压缩草丛高度的精度评价

准确估计牧草质量 (HM) 对于优化草的利用和增加以牧场为基础的畜牧业的利润至关重要。上升板计 (RPM) 用于根据平均压缩草丛高度 (CSH) 预测 HM。采样分辨率和分布是确定 HM 空间异质性的主要参数。RPM 没有明确的采样协议。本研究的目的是：调查牧场内 HM 的空间变化，确定准确预测平均 HM 所需的 RPM 测量次数，并评估 RPM 在测量可重复性方面的精度。在两个放牧季节，对受控地块和放牧围场进行了密集的 CSH 测量和 HM 参考切割。草地异质性被估计为 CSH 的变异系数 (CV)，并与根据 HM CV 经验得出的“真实”草地异质性进行比较。进行了回顾性分析模拟，以确定各种降低的测量分辨率对估计平均 CSH 误差的影响。对草样进行了重复测量分析，以确定 RPM 测量系统的精度。结果表明，牧草异质性在整个生长季节变化了 36%，并受到放牧、施肥、草地组成和季节性的影响。通过以随机分层方式记录每公顷 24 次测量，平均 CSH 可以估计在 5% 的相对预测误差内。经计算，RPM 测量重复性的标准偏差为 4.34 毫米。