Assessing urea efficiency in paddy using vegetation indices: A comparative study of super nano urea and conventional urea

This study evaluates the efficiency of solid and liquid Super Nano Urea (SNU) and conventional urea in rice, focusing on physiological responses, grain quality and vegetation indices. A field experiment during Rabi and Kharif 2024 compared 13 fertilization strategies, including 100 %, 75 % and 50 % of the Recommended Dose of Nitrogen (RDN) using SNU granules, with or without two foliar sprays of 0.7 % liquid SNU at tillering and panicle initiation stages. Parallel treatments used conventional urea at equivalent nitrogen (N) levels, also with and without foliar sprays. A no-fertilizer control was included. Growth parameters such as Plant Height (PH), Leaf Area Index (LAI), Soil Plant Analysis Development (SPAD) values and vegetation indices including Normalized Difference Vegetation Index (NDVI), Normalized Difference Red Edge Index (NDREI), Ratio Vegetation Index (RVI) and Green Normalized Difference Vegetation Index (GNDVI), were recorded. The results showed that foliar application of SNU significantly enhanced Nitrogen Use Efficiency (NUE). For instance, SNU at 100 % RDN + 2 sprays yielded 6318 kg ha-1, versus 6150 kg ha-1 without sprays. Similarly, conventional urea at 100 % + 2 sprays produced the highest yield (6400 kg ha-1), outperforming its no-spray counterpart (6273 kg ha-1). Foliar sprays improved nutrient uptake, panicle traits and Grain Yield (GY). Despite limited distribution and regulatory hurdles for SNU, the results show that combining conventional urea with foliar sprays provides a high-performing, sustainable nitrogen management strategy.