Abstract
Accurate prediction of dry matter yield (DMY) in pastures is crucial for grazing management. Estimates by means of rising-plate-meter measurements are a time-effective way to determine DMY in pastures. It has been shown previously that the accuracy of DMY estimation can be improved by taking the day of the year (DOY) into account. In this study we replace DOY by Growing Degree Days (GDD) and compare both approaches. €e study was performed in South Tyrol (NE Italy), where 830 paired measurements of DMY and compressed sward height (CSH) by means of rising plate meter (Grasshopper®) were taken in three different paddocks during three growing seasons (2020, 2021 and 2023) covering the whole grazing season from April to the start of November. Statistical predictive models for DMY were stepwise forward developed by linear models starting from a baseline model including paddock and CSH. Both approaches (GDD and DOY) resulted in final models predicting a curvilinear increase of DMY with increasing CSH, a stronger slope towards the end of the CSH range and a fluctuating effect of the growing season. Although GDD proved to be a valid alternative to DOY, it did not increase the accuracy of statistical models estimating DMY based on CSH.