Comparing Field- and Drone-Based Assessments to Measure Forage Production

Pasturelands are considered land dedicated to the production of livestock forage for harvest by grazing, cutting, or both. Estimating forage production aids with decisions on grazing management. Drone data collection is increasingly being used to collect high-resolution imagery over large areas in rangelands. Our objective for this study was to compare forage estimations from a traditional doubling-sampling method and drone double-sampling data with total forage production. We flew two study sites in Freestone County, Texas, USA on June 12 and June 20, 2022, respectively. We selected and marked six sets of five quadrats (0.25 m²) throughout each field based on a categorical scale of forage height of 1–5, with 1 being the lowest forage height present and 5 being the highest. After the flights, the quadrats were clipped, dried, and weighed to estimate forage mass production. Each field was then cut, cured, and baled into round bales; the bales produced determined the total forage production for each field. Drone imagery was processed to create a canopy height model to calculate plant heights, which were classified using the field double-sampling categories. The area for each category was calculated and multiplied by the dry weights collected from the quadrats to predict the total forage production for each category. The fields produced 5 889 and 2 219 kg·ha −1 . The drone double-sampling forage mass was 5 204 ± 367 kg·ha −1 and 2 490 ± 152 kg·ha −1 ; and the field double-sampling, 5 568 ± 365 kg·ha −1 and 1 992 ± 124 kg·ha −1 . Both methods were less than 1.5-bale difference for each field. Therefore, drone data may be used as a new tool for estimating forage production, aiding ranchers with management decisions. Forage estimations via drones will provide opportunities to cover larger areas, in a repeatable and on-demand approach.