Effects of Char and Amendments on Soil Properties and Sugar Beet Yield in Sandy Clay Loam Soil

Carbon-rich products such as biochar and coal char have emerged as promising soil amendments to improve soil properties and support plant growth in semiarid climates. Coal char is produced from the pyrolysis of coal, while biochar is a biomass-derived product from pyrolysis. A two-year field study was conducted to evaluate the comparative impacts of coal char, biochar, inorganic fertilizer, and manure amendments on soil properties, plant growth indices, and soil and plant nutrient dynamics in a semiarid, sandy clay loam soil in Wyoming, USA. The study demonstrates the value of multivariate approaches for capturing the complex, interactive effects of amendments and plant covariates on crop performance. Results show that, while char and amendment treatments did not significantly alter soil pH, EC, or CEC, both char type and fertilizer amendments significantly affected soil nutrient availability and plant tissue nutrient concentrations. Multivariate multiple linear regression (MMLR) showed coal char at 22–44 Mg ha−1 increased yield by up to 4.4 t ha−1, with higher Normalized Difference Red Edge (NDRE) and leaf sulfur (S) concentrations associated with reduced sugar loss to molasses. Our results suggest that coal char has potential as a sustainable amendment for improving sugar beet productivity in semiarid, sandy clay loam soils, especially when integrated with inorganic fertilizer and manure. Further research is needed to assess the variability of coal char and biochar and their cumulative impacts on soil health and productivity across different cropping systems.