Optimization and validation of leaf color chart, SPAD meter and GreenSeeker thresholds for precise nitrogen management in wheat cv. Karan Vandana

Nitrogen inefficiency in cereal cropping systems leads to suboptimal yields, environmental pollution and reduced fertilizer recovery rates. Non-destructive tools, including the leaf color chart (LCC), Soil plant analysis development meter (SPAD) and GreenSeeker, enable real-time assessment of canopy nitrogen status and site-specific fertilizer recommendations. Therefore, field experiments were conducted at Research farm of Sher-e-Kashmir University of Agricultural Sciences and Technology, Jammu during rabi season 2023–24 and 2024–25 with 14 treatments on sandy clay loam soil in randomized block design (RBD) and 3 replications. The results revealed that significantly higher growth, yield attributes, yield and N uptake were found with the application of LCC ≤ 5 at 20 kg N ha-1 (T6) which was statistically at par with LCC ≤ 4 at 20 kg N ha-1 (T4), GreenSeeker-directed N application ≤ 0.8 normalized difference vegetation index (NDVI) at 20 kg N ha-1 (T14) and sufficiency index-based N application ≤ 95 % at 20 kg N ha-1 (T10) during both the years. Linear regression analysis conducted over 2 years demonstrated that the LCC value had a significant positive correlation with grain yield (GY) at 5 % significance level with an average correlation coefficient of 0.92.