Development of a Robust Sensor Calibration for a Commercially Available Rising Platemeter to Estimate Herbage Mass on Temperate Seminatural Pastures

Rising platemeters are commonly used in Ireland and New Zealand for managing intensive pastures. To assess the applicability of a commercial rising platemeter operating with a microsonic sensor to estimate herbage mass with its own equation, the objectives were (i) to validate the original equation; (ii) to identify possible factors hampering its accuracy and precision; and (iii) to develop a new equation for heterogeneous swards. A comprehensive dataset (n = 1511) was compiled on the pastures of dairy farms. Compressed sward heights were measured by the rising platemeter. Herbage mass was harvested to determine reference herbage availability. The adequacy of estimating herbage mass was assessed using root mean squared error (RMSE) and mean bias. As the adequacy of the original equation was low, a new equation was developed using multiple regression models. The mean bias and the RMSE for the new equation were overall low with 201 kg dry matter/ha and 34.6%, but it tended to overestimate herbage availability at herbage mass < 500 kg dry matter/ha and underestimate it at >2500 kg dry matter/ha. Still, the newly developed equation for the microsonic sensor-based rising platemeter allows for accurate and precise estimation of available herbage mass on pastures.

Field Evaluation of a Rising Plate Meter to Estimate Herbage Mass in Austrian Pastures

Pasture management is an important topic for dairy farms with grazing systems. Herbage mass (HM) is a key measure, and estimations of HM content in pastures allow for informed decisions in pasture management. A common method of estimating the HM content in pastures requires manually collected grass samples, which are subjected to laboratory analysis to determine the dry matter (DM) content. However, in recent years, new methods have emerged that generate digital data and aim to expedite, facilitate and improve the measurement of HM. This study aimed to evaluate the accuracy of a rising plate meter (RPM) tool in a practical setting to estimate HM in Austrian pastures. With this study, we also attempted to answer whether the tool is ready for use by farmers with its default settings. This study was conducted on the teaching and research farm of the University of Veterinary Medicine in Vienna, Austria. Data were collected from May to October 2021 in five different pastures. To evaluate the accuracy of the RPM tool, grass samples were collected and dried in an oven to extract their DM and calculate the HM. The HM obtained from the grass samples was used as the gold standard for this study. In total, 3796 RPM measurements and 203 grass samples yielding 49 measurement points were used for the evaluation of the RPM tool. Despite the differences in pasture composition, the averaged HM from the RPM tool showed a strong correlation with the gold standard (R2 = 0.73, rp = 0.86, RMSE = 517.86, CV = 33.67%). However, the results may not be good enough to justify the use of the tool, because simulations in economic studies suggest that the error of prediction should be lower than 15%. Furthermore, in some pastures, the RPM obtained poor results, indicating an additional need for pasture-specific calibrations, which complicates the use of the RPM tool.

The Effect of Kurzrasen and Strip-Grazing on Grassland Performance and Soil Quality of a Peat Meadow

Due to the increased herd size in the Netherlands, there is need to assess the performance of different grazing systems at high stocking densities. The objective of the current experiment was to assess the effect of two extreme grazing systems, kurzrasen (continuous grazing at 3–5 cm sward height) and strip-grazing at a high stocking rate, on grass production and quality, grass morphology and sward density, root development and load bearing capacity on peat soil. To this end, a two-year grazing trial with four herds of 15 cows on 2 ha each was conducted. Kurzrasen showed 18% lower herbage dry matter production on average compared to strip-grazing. The yield penalty of using a shorter regrowth period under kurzrasen was limited due to the strong response in grass morphology, resulting in a dense and lamina-rich sward. There was a small decline in root density at 10 cm soil depth, but no evidence of a lower root density at 20 cm soil depth for kurzrasen compared to strip-grazing. Sward density was higher for kurzrasen compared to strip-grazing, which had a positive impact on load bearing capacity. This is an important feature on peat soils, where load bearing capacity is often limited.

Correcting fresh grass allowance for rejected patches due to excreta in intensive grazing systems for dairy cows

Dairy farms with intensive grazing systems combine grazing with supplemental feeding, which can be challenging because an incorrect balance between fresh grass allowance and feed supplementation results in inefficient use of the pasture, lower feed efficiency, and potential decreases in animal production. When estimating fresh grass allowance, we currently do not correct for the formation of rejected patches (RP) surrounding excreta, which can lead to overestimation of the potential fresh grass intake and hampers optimal grazing. In this study, therefore, we aim to quantify the formation of RP in intensive grazing systems and improve the quantification of fresh grass allowance. To do so, we studied 2 grazing systems (i.e., compartmented continuous grazing and strip grazing) that differ in key grazing characteristics, such as pre- and post-grazing heights and period of regrowth. The experiment was performed from April to October in 2016 and 2017 with 60 dairy cows at a fixed stocking rate of 7.5 cows/ha. Average pre-grazing grass height was measured with a rising plate meter. To quantify the formation of RP after grazing, individual grass height measurements were conducted after grazing and classified as RP or not, based on visual assessment. Our analysis showed that the average percentage of grassland covered with RP increased from around 22% at the end of May to around 43% at the end of July/beginning of August, and these percentages do not differ across grazing systems. The percentage of grassland covered with RP should be subtracted from the total grazed area to better estimate true fresh grass allowance.