Evaluation of Nutrient Levels, Optical Sensors and Decision Support Tools for Nitrogen Optimization in Rice during Dry Season

Improving the efficiency of nitrogen utilization in rice is vital for achieving significant crop yields with minimum harm to the environment. To tackle this challenge, various portable optical sensors and decision-support tools have been emerging in recent times. However, there is currently a lack of comprehensive assessment and comparison of these tools with different levels of fertilizer recommendation with and without additional supplementation of nano urea.

The current study was carried out during the dry season of 2021 and 2022 at the P.G. Experimental Farm of Centurion University of Technology and Management. The investigated treatments encompassed the following: T₁: Absolute control, T₂: 90-45-45 (N-P₂O₅-K₂O kg/ha), T₃: 120-60-60 (RDF), T₄: 150-75-75, T₅: T₂+NU @ 2 ml/L at panicle initiation, T₆: T₃+NU @ 2 ml/L at panicle initiation, T₇: N application at LCC ≤ 3, T₈: N application at LCC ≤ 4, T₉: N application at SI < 90%, T₁₀: Nutrient Expert (TY: 5.5 t/ha), T₁₁: Rice crop manager (TY: 5.5t/ha) which were allocated in randomized block design with three replications.

The findings showed that implementing nitrogen (N) application when the sufficiency index (SI) is below 90% led to a significant 16.85% boost to grain yield of rice compared to the application of 120-60-60 at fixed intervals as per the standard recommendation. In the former approach, 150 kg N/ha was applied in four splits. However, N application at a leaf color chart (LCC) value of 4 or less was considered efficient, with maximum agronomic efficiency (18.22 and 19.22 kg grain/kg N applied) and recovery efficiency (43.27% and 50.25%) observed in 2021 and 2022, respectively since, this approach resulted in a comparable yield increase and nitrogen absorption with a reduced nitrogen input.