- Publication Year: 2026
- Page(s): 72 - 84
Sugar beet is a major sugar crop in temperate
regions and rapid, high-throughput, and accurate estimation of
field phenotypes is essential for variety selection and production
optimization. In this paper, ten commercial sugar beet varieties
adapted to high latitudes are investigated using unmanned aerial
vehicle (UAV) based red-green-blue (RGB), multispectral, and
thermal infrared imaging across multiple growth stages. Canopy
structural, texture, spectral, and temperature features are
extracted, and three machine learning algorithms, random forest
(RF), partial least squares (PLS), and support vector machine
(SVM), are used to predict sugar content, root fresh weight, and
yield. The results show that all three methods estimate sugar
content well, with relative root mean square error (rRMSE)
values below 11.0%, while RF and PLS outperform SVM. Multispectral
features provide higher accuracy than RGB features, and
multi-sensor feature combinations generally improve sugar
content prediction compared with single-sensor inputs. For root
fresh weight, SVM slightly outperforms RF and PLS, and RGB
features are more informative than multispectral features. The
integration of thermal infrared features does not notably improve
RF or PLS models, but the combination of multispectral and
thermal infrared features achieves the best SVM performance
( R2=0.58, RMSE = 75.3 g, and rRMSE = 23.7%). For yield
estimation, RF achieves the highest accuracy, with rRMSE values
ranging from 15.4% to 18.8%. Yield prediction accuracy increases
as the time of image acquisition approaches harvest, and combining
multi-temporal data from periods close to harvest further
improves model performance. Overall, multi-sensor UAV data
can effectively estimate sugar content, root fresh weight, and yield
in sugar beet, providing a useful approach for phenotypic analysis,
precision management, and variety selection.