Research on Estimating Rice Canopy Height and LAI Based on LiDAR Data.

Rice canopy height and density are directly usable crop phenotypic traits for the direct estimation of crop biomass. Therefore, it is crucial to rapidly and accurately estimate these phenotypic parameters. To achieve the non-destructive detection and estimation of these essential parameters in rice, a platform based on LiDAR (Light Detection and Ranging) point cloud data for rice phenotypic parameter detection was established. Data collection of rice canopy layers was performed across multiple plots. The LiDAR-detected canopy-top point clouds were selected using a method based on the highest percentile, and a surface model of the canopy was calculated. The canopy height estimation was the difference between the ground elevation and the percentile value. To determine the optimal percentile that would define the rice canopy top, testing was conducted incrementally at percentile values from 0.8 to 1, with increments of 0.005. The optimal percentile value was found to be 0.975. The root mean square error (RMSE) between the LiDAR-detected and manually measured canopy heights for each case was calculated. The prediction model based on canopy height (R2 = 0.941, RMSE = 0.019) exhibited a strong correlation with the actual canopy height. Linear regression analysis was conducted between the gap fractions of different plots, and the average rice canopy Leaf Area Index (LAI) was manually detected. Prediction models of canopy LAIs based on ground return counts (R2 = 0.24, RMSE = 0.1) and ground return intensity (R2 = 0.28, RMSE = 0.09) showed strong correlations but had lower correlations with rice canopy LAIs. Regression analysis was performed between LiDAR-detected canopy heights and manually measured rice canopy LAIs. The results thereof indicated that the prediction model based on canopy height (R2 = 0.77, RMSE = 0.03) was more accurate.

Study on the movement mechanism of rice stem under the action of canopy-opening device based on explicit dynamics simulation.

The dense canopy of rice causes attenuation of droplet dispersion during pesticide application. The canopy-opening device can increase droplet deposition in the middle and lower canopy of rice by causing disturbance to the rice canopy. However, the conditions for use of the canopy-opening device are difficult to determine. Rice morphological structure parameters and material parameters were measured to study the movement mechanism of the rice stems under the action of the canopy-opening device, and the canopy-opening process was then simulated using the explicit dynamic method. The simulation scene of the rice canopy-opening process considered the combination of three different heights and three different driving velocities of the canopy-opening device. The movement mechanism of the rice stems under the operation of the canopy-opening device was investigated, and the entire movement process was separated into two stages: contact and oscillation. The simulation results and high-speed photography experimental results show a strong correlation, with a correlation coefficient of 0.733. The simulation results indicate that when the canopy-opening device is closer to the ground and the driving velocity is higher, the disturbance to the rice stem during the contact stage is stronger. However, for the oscillation stage, there exists a critical value for both the height and driving velocity of the canopy-opening device. During the oscillation stage, there is a critical value for both the height and driving velocity of the canopy-opening device. The numerical-based explicit dynamics approach was employed in this work to investigate the rice canopy motion mechanism, and this study has a definite reference value for the investigation of complicated motion mechanisms in the field crop production process.