Self-propelled applicator for urea–ammonium nitrate (UAN) solution in wheat

Late-stage foliar nitrogen application in narrow-row wheat using manual spraying causes significant trampling losses that reduce agronomic benefits. This study developed and evaluated a self-propelled urea–ammonium nitrate applicator (SPUANA) to improve foliar nutrient application efficiency while minimizing crop damage in smallholder farming conditions. Laboratory optimization (CRD) and field trials (RBD, three replications) assessed spray uniformity, droplet characteristics, field performance, trampling losses, grain yield and economic feasibility. Optimized operating conditions of 147 kPa pressure, 50 cm nozzle spacing and 50 cm boom height achieved a coefficient of variation of 36.2%, meeting BIS uniformity standards. Under these conditions, the SPUANA produced a volume median diameter of 276.25 µm, droplet density of 46.2 drops cm−2 and field efficiency of 61.1%. The applicator delivered an effective field capacity of 1.71 ha h−1 with operational costs of Rs. 372 h−1 and a payback period of 2.86 years. Compared with manual knapsack spraying, SPUANA reduced trampling losses from 5.8% to 1.2%, resulting in a net grain yield increase of 2.7 q ha−1 (5.5% improvement). The primary advantage of SPUANA is significantly reducing mechanical crop damage while maintaining effective spray application. This represents a practical and economically viable solution for smallholder wheat farmers to improve foliar fertilizer application efficiency, protect yields and enhance farm profitability.