Sweet sorghum biomass, brix content and estimated ethanol yield response to inorganic fertiliser, biochar, compost and biochar–compost blend in marginal rainfed soils

Abstract

Sustainable production of bioenergy crops, such as sweet sorghum, is essential for supporting clean energy and biofuel development, particularly under marginal and rainfed conditions. This study evaluated the effects of organic amendments (biochar, compost and a biochar–compost blend (1:1)), compared to inorganic fertiliser on fresh biomass, brix content and estimated ethanol yield of sweet sorghum. Organic amendments were applied at 7 Mg C ha⁻¹ each season, while inorganic fertiliser was applied at 300 kg ha⁻¹ of 2:3:4 (30) with a 400 kg ha⁻¹ limestone ammonium nitrate topdressing. The organic amendments significantly improved crop performance compared to inorganic fertiliser. The application of organic amendments increased sweet sorghum fresh biomass by 27%–50%, brix content by 13.89%–48.43% and estimated ethanol yield by 58%–100% compared to inorganic fertiliser, respectively. Among the organic amendment treatments, the biochar–compost blend produced the highest values across all agronomic parameters, demonstrating its potential benefits as a sustainable fertiliser management for sweet sorghum production as a bioenergy crop in rainfed conditions. However, future research should integrate the biochar–compost blend with conservation practices to develop holistic sustainable production of bioenergy crops such as sweet sorghum under rainfed and marginal soils.