Evaluation of LiDAR scanning for measurement of yield in perennial ryegrass

Seasonal dry matter yield (DMY) is highly valued in pastoral systems, making it a major target for plant breeders. However, measuring and selecting for DMY is a major bottleneck in breeding, requiring methods that are laborious, destructive, and/or imprecise. A LIDAR-based computerised scanner developed in Canterbury was evaluated in the Waikato on perennial ryegrass paired-row breeding plots in a plant breeding trial with 630 entries at one location. At eight timepoints, all plots were scanned prior to mechanical defoliation and recording of fresh weight yield (FWY) and DMY data on a random subset of plots. Data on 1206 FWY and 504 DMY samples were compared with LIDAR scan results on a seasonal basis by regression. Winter, Spring, Summer and Autumn correlation with FWY were r2=0.81, 0.92, 0.94 and 0.90, respectively, and with DMY r2=0.87, 0.73, 0.87 and 0.79, respectively. These data indicate LIDAR estimation of DMY is accurate within seasons for the paired-row breeding plots, although it is sensitive to large changes in dry matter content (%) among seasons, which may require seasonal algorithms to correct for this variation. In general, the scanner is useful in removing a major bottleneck in perennial ryegrass breeding, and may have application for agronomy and farm management in cases where precise non-destructive real-time estimation of DMY are of value.