Variable rate technology offers a sustainable, efficient, and cost-effective solution for fertilizer application. A study was conducted to design and develop a variable rate fertilizer applicator to detect real-time deficiency of N within the field and apply it per requirement of the crop. The microcontroller system was designed to receive a signal from the N sensor and send a signal to the pulse-width-modulation valve to vary the rotational speed of the hydraulic motor resulting in variation in the rotation of the metering mechanism drive shaft based on the recommended amount of fertilizer. During the field study, three replications were conducted, each of which was divided into four plots. The response time between the N sensing and fertilizer discharging fell within the range of 3.49 to 4.90 s. Fertilizer applied using the developed variable rate applicator indicated that when the fertilizer rate is increased from N1 to N4 (kg ha⁻¹), NDVI increased from 0.56 to 0.78 and drive shaft rotational speed decreased from 20 to 0 rpm in order to apply the fertilizer at a rate of 0.00 instead of 78.36 kg ha⁻¹. Using the developed applicator demonstrates that this technology could reduce environmental impact, making farming more sustainable.

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.

Manual transplanting, a pre-dominant practice in almost all the paddy growing areas in India, is laborious, burdensome, and has many expenses on raising, settling, and transplanting nursery. The transplanting process’s limitations motivated the replacement of conventional paddy transplanting methods. The study was divided into two phases. The first phase included laboratory testing of three levels of metering mechanisms, namely cell type (M1) with 10 cells grooved around a circular plate having a 13 cm diameter, inclined plate (M2) containing 24 U shaped cells provided on an 18 cm diameter plate, and fluted roller (M3) with 10 flutes on a 5 cm diameter shaft. The testing matrix included a missing index, multiple index, and seed damage with forward speeds (2.5, 3.0, and 3.5 km/h), and pre-germination levels of 24 h soaked (P1), 24 h pre-germinated (P2), and 36 h pre-germinated paddy seeds (P3)). The second phase included selecting the best combination obtained from the laboratory study and developing a new efficient planter for the puddled field. The inclined plate metering mechanism operating at 2.5 km/h for 24 h pre-germinated seeds was reported most efficient from the first phase. Therefore, a self-propelled 8-row planter equipped with an inclined plate metering mechanism having a row-to-row spacing of 22.5 cm was developed, fabricated, and evaluated in the puddled field. The designed planter was assessed on two different soils: sandy loom (ST1) and clay loom (ST2) and at two different hopper fill levels as ½ filled hopper (F1) and ¾ filled hopper (F2). The number of plants per square meter and hill-to-hill spacing was measured. The on-field evaluation revealed that the number of plants per square meter was non-significantly affected by the type of soil but was significantly affected by hopper fill.

Field evaluation of an auto-rotate gun sprayer and comparison with a knapsack sprayer was carried out to control whitefly Bemisia tabaci (Genn.) in the cotton crop. Two experiments were conducted at six locations of farmers' fields in southwestern (cotton-growing region) of Punjab state. The number of adult whiteflies was counted before and 3, 7 and 10 days after spray. Water-sensitive papers were attached at upper and under side of the leaves at three different points (top, middle and bottom) of plant canopy to find sprayers performance parameters, viz. droplet diameter, droplet density, per cent area covered and volume of spray deposition. Droplet density, area covered and volume of spray deposition were found significantly higher in case of the auto-rotate gun sprayer as compared to that of a knapsack sprayer. However, the volume median diameter of droplets was found significantly lesser in case of an auto-rotate gun sprayer, i.e. 286.95 mu m as compared to the knapsack sprayer, i.e. 347.85 mu m. The per cent whitefly control in the cotton crop in first experiment was found as 68.06 % and 65.90 % for auto-rotate gun and knapsack sprayer, respectively, by using pyriproxyfen 100 g active ingredient (g a.i.)/ha. Although in the second experiment the per cent whitefly control for auto-rotate gun sprayer was significantly higher, i.e. 83.27 % as compared to knapsack sprayer having 70.87 % control by using flonicamid 75 g a.i./ha. However, the bio-efficacy of auto-rotate gun sprayer was found higher for the both experiments as compared to the knapsack sprayer. The cost of operation of the auto-rotate gun sprayer was found to be US$4.11/ha as compared to knapsack sprayer with $6.85/ha. The cost, labour and time-saving in the spraying with the auto-rotate gun sprayer as compared to the knapsack sprayer was found to be 39.98, 93.44 and 96.64 %, respectively.

Spraying is very tedious and time consuming operation. There is a need of an efficient, precise and high capacity machine for spraying. The pesticide with conventional sprayers is not so effective because non-uniform spray and of lesser width of coverage. Distribution of pesticide is not uniform especially at the underside of the leaves. The pest can be controlled effectively if pesticides are applied properly at the right rate, right time and on the target by right equipment. In field crops like cotton the pest attacks is on the lower side of the leaves during vegetative as well as reproductive stages of the cotton crop. The sprays with conventional sprayer do not enter at the bottom of the plant canopy and at lower side of the leaves. Different type of sprayers are being developed especially for the control of white fly in cotton crop. These sprayers can also be used for crops like sugarcane, potato etc. Air assisted electrostatic sprayer, Auto rotating gun type sprayer, Multipurpose high clearance sprayer and even drones are now a days used for spraying in cotton crop. Multipurpose high clearance sprayer mostly preferred by the farmers has three types of spraying arrangements namely auto rotate gun, boom type and drop up type nozzles can work at all stages of the crop and saves time, labor and cost of operation as well as it reduces drudgery of the operation. Selection of nozzle is also important for these type of sprayers. Automatic controller can be fitted on these sprayers for adjusting the discharge and to reduce missing or overlapping of spray.