Non-destructive estimation of soluble sugar content in fodder sorghum via ground-based multispectral sensing

Rapid and non-destructive assessment of soluble sugar content in fodder sorghum is important for identifying optimum harvest conditions and improving its potential as a bioethanol feedstock. The present study evaluated ground-based multispectral sensing for estimating Brix content in fodder sorghum under contrasting nutrient management systems. A field experiment was conducted at the Malad Research Farm, ICAR–NIASM, Baramati, Maharashtra, on Vertisol soil using a randomized block design with seven nutrient management treatments (T1-T7) and three replications. Observations were recorded at five critical growth stages (30, 45, 60, 75, and 90 DAS). Canopy spectral measurements were acquired using a Parrot Sequoia multispectral camera to calculate NDVI, GNDVI, NDRE, and NGRDI. Concurrent measurements of SPAD chlorophyll, leaf nitrogen (N), and Brix content were obtained as ground-truth parameters. Red-edge and green-based indices showed greater sensitivity to crop physiological status than conventional visible-band responses. Pearson correlation and simple linear regression analyses were used to evaluate relationships between spectral indices and Brix content, with NDRE exhibiting strong potential for Brix estimation (R2 = 0.91). The study demonstrates that ground-based multispectral sensing provides a rapid, non-destructive approach for monitoring sugar accumulation in fodder sorghum to support precision harvest management.