International Journal of Plant & Soil Science

Efficient nitrogen management is important for improving rice productivity while reducing avoidable nitrogen losses in lowland rice ecosystems. A field trial was conducted during the Kharif season of 2021 in farmers’ fields in Nalbari district, Assam, to evaluate Leaf Colour Chart (LCC)-based nitrogen management in transplanted Sali rice (variety Ranjit Sub-1). The experiment compared two treatments: T1, LCC 4 with integrated nutrient management (INM), comprising Azospirillum and PSB at 4 kg/ha each, rock phosphate at 10 kg/ha and the recommended dose of potassium at 40 kg/ha; and T2, the recommended dose of NPK at 60:20:40 kg/ha. In T1, nitrogen was applied through three split applications of urea based on LCC readings after transplanting, without basal nitrogen application. The LCC 4 with INM treatment improved yield attributes, including plant height, tiller number per hill, panicle length, filled grains per panicle and test weight, compared with the recommended fertiliser dose. Grain yield increased from 4.72 t/ha under T2 to 5.20 t/ha under T1, while straw yield increased from 18.52 to 23.50 t/ha. The LCC-based treatment recorded higher nitrogen use efficiency (47.17 kg grain/kg N fertiliser) and agronomic efficiency of nitrogen (22.17 kg grain/kg N) than the recommended fertiliser dose. It also saved 24.75 kg/ha urea, equivalent to 11.38 kg/ha chemical nitrogen, and increased grain yield by 10.16% over T2. Economic returns were also higher under T1, with a benefit:cost ratio of 2.6 compared with 2.3 under T2. The findings indicate that LCC 4 with INM can support need-based nitrogen application, improve fertiliser efficiency and enhance profitability in transplanted Sali rice under farmers’ field conditions.