Variable-rate technology (VRT) may reduce input costs, increase crop productivity and quality, and help to protect the environment. The present study was conducted to evaluate the performance of a variable-rate fertilizer applicator for rice (Oryza sativa L.). Three replications were conducted, each of which was divided into four plots. Field performance of the system was assessed at different nitrogen levels (N1 to N4, i.e., 75, 125, 175, 225 kg ha⁻¹), growth stages (tillering, panicle initiation, heading), and heights (40, 60, 80, 100 cm) of the sensor from the crop canopy. Fertilizer rate was at minimum 12.59 kg ha⁻¹ at 10 rpm of drive-shaft rotational speed and at maximum 50.41 kg ha⁻¹ at 40 rpm. The system response time was within the range of 3.53 to 4.93 s, with overall error ranging between 0.83% to 4.92%. Across different growth stages, when fertilizer rate was increased from N1 to N4, NDVI increased from 0.49 to 0.69. Hence, drive-shaft rotational speed is decreased from 25 to 7 rpm to shift the application rate from 30.83 to 9.15 kg ha⁻¹. There was a 45% reduction in total fertilizer rate applied by the system, with respect to the recommended rate.

The development of novel technologies in modern agriculture is predominantly focused on increasing productivity of field operations and reducing manual labour. The tractor operators are required to ensure precise and efficient movement of tractors, along with attached implements to avoid economic losses, which often results in physiological damage to tractor operators’ health. In this context, employment of satellite-based navigation systems on tractors to perform different farm operations may be a suitable technology to decrease the probability of skipping and overlapping of areas which in turn increases operator efficiency. The current study endeavours to compare the relative performance of two commercially available navigation systems viz., offset value guidance system (N₁) and LED lightbar guidance system (N₂) installed on tractors for tillage operations with respect to tractor operated without navigator-assistance. The experiments were conducted by two operators (O₁ and O₂). The results of comparative analyses clearly reveal lower percentage of skipped or missed areas (O₁: 4%, O₂: 3.33%) during N₁ navigator-assisted operations and (O₁: 3.7%, O₂: 5.5%) during N₂navigator-assisted operations, as compared to without navigator assistance (O₁: 17.33%, O₂: 12.7%). Similarly, overlapped areas also showed marked decrease during N₁ (O₁: 2.33%, O₂: 3.5%) and N₂ (O₁: 3.5%, O₂: 3.83%) operations, with respect to ‘without navigator assistance’ (O₁: 10.17%, O₂: 13.83%) operations. The study further suggests that use of navigators significantly increases the area of soil pulverization due to lesser missing and decreases the fuel wastage by reducing overlapped area. Overall performance can be further improved by increasing the familiarity of operators with navigator instructions.