Mature Rice Biomass Estimation Using UAV-Derived RGB Vegetation Indices and Growth Parameters

The biomass of rice at maturity serves as a vital indicator for assessing overall productivity, and its accurate estimation holds significant importance for ensuring food security and promoting sustainable agriculture. To improve the precision of current biomass estimation methods for mature rice, this study employed support vector regression to integrate RGB vegetation indices from rice canopy images with growth parameters, thereby developing a biomass estimation model. The model was validated by applying it to the experimental area. The results indicated that screening RGB vegetation indices and combining them with growth parameters enhanced estimation accuracy. Specifically, the model integrating RGB vegetation indices (g, RGBVI) with rice plant height and moisture content demonstrated high estimation accuracy (<i>R</i>² = 0.78, <i>RMSE</i> = 0.32 kg/m²). The absolute difference between the estimated and measured biomass values ranged from 0.15 to 0.39 kg/m². Additionally, the estimated biomass showed a strong correlation with yield (<i>R</i>² = 0.86), with a fitted equation of <i>y</i> = 0.04<i>x</i> + 0.59. These results suggest that the model is reliable for large-area estimation of mature rice biomass. However, the degree of rice maturity and the lodging phenomenon were identified as the primary factors influencing the precision of model application. Overall, integrating RGB vegetation indices of the rice canopy, obtained via UAV-based remote sensing technology, with growth parameters provides an effective method for estimating mature rice biomass and offers a valuable reference for efficient yield estimation.