<p>A field experiment was conducted at the Regional Agricultural Research Station, Anakapalle, from 2020–2021 to 2023–2024 for four consecutive years and validated at farmers’ fields as on-farm testing (OFT) during 2024–2025. The effect of in situ cane trash management coupled with microbial consortia and molasses as a substrate significantly influenced the yield and yield attributes of sugarcane, along with soil fertility status. Results revealed that 100% NPK recorded yields (75.22 and 10.14 t ha⁻¹) on par with 75% NPK+ trash incorporation (76.67 and 10.28 t ha⁻¹). Cane and sugar yields were further increased with 100% NPK along with trash incorporation (79.28 and 10.40 t ha⁻¹, respectively). A fertilizer saving of up to 25% was achieved through in situ incorporation of cane trash during all four years. The addition of trash in conjunction with chemical fertilizers significantly improved the soil organic carbon status compared to fertilizer-alone and trash-alone treatments. Soil organic carbon increased from its initial level of 0.56% to 0.64% in the T₄ treatment, amounting to an average increase of 12.5% within a period of four years. A positive influence was also observed on the available soil macronutrient status, i.e., available nitrogen, phosphorus, and potassium increased to 246, 93, and 260&#xa0;kg&#xa0;ha⁻¹, respectively, over the initial values of 232, 86, and 241&#xa0;kg&#xa0;ha⁻¹. An increase in available micronutrient content was also recorded under trash-incorporated plots. On-farm testing of 100% NPK and 75% NPK with in situ cane trash incorporation at farmers’ fields revealed that cane and sugar yields were numerically superior with 75% NP + cane trash incorporation and were on par with 100% NPK. It can be concluded that in situ decomposition of cane trash using molasses and/or microbial consortia in sugarcane can reduce the requirement of chemical fertilizers (NPK) by 25% without adversely affecting soil fertility and crop productivity.</p>