Evaluation of leaf colour chart for need-based nitrogen management in rice, maize and wheat in north-western India

Large field to field variability in inherent nitrogen (N) supply restricts efficient fertilizer N use when broad based blanket recommendations are used in cereals. Field experiments were conducted for 11 years (2000–2011) to evaluate threshold leaf colour greenness to guide in-season need based fertilizer N top-dressings in different rice, wheat and maize varieties grown in wide range of agro-climatic conditions in Punjab. Evaluation of need-based fertilizer N management strategy using leaf colour chart (LCC) at 461 on-farm experiments in rice, 96 on-farm experiments in wheat and 23 on-farm experiments in maize suggested that blanket recommendation did not lead to adequate synchronization of N supply with actual crop N demand. LCC based N management could adequately take care of field to field and temporal variation in N supply to plant and thus holds promise for efficient fertilizer N use in rice, wheat and maize. The LCC based fertilizer N management always produced grain yield equivalent or more than the blanket N recommendation with the average saving of 51, 20 and 29 kg N ha⁻¹, respectively, in rice, maize and wheat. The LCC being a simple, economical and farmer friendly tool can be used even by illiterate farmers for making instant decision to supply N as per crop need.