Flexible orifice seed metering plate to address variability in seed shape, size and orientation enhances field performance of a pneumatic planter

Abstract

Pneumatic planters are widely adopted in precision agriculture due to their superior field performance and minimal seed damage. However, variations in seed size, shape, and orientation can affect the ability of each orifice to pick and release a single seed accurately. Seed metering units typically incorporate seed cut-off and knock-out devices to improve singulation and ensure timely seed dropping, enhancing the quality feed index and reducing the precision index. These auxiliary devices—whether mechanical, electronic, pneumatic, or magnetic—increase system complexity, require skilled operation, necessitate additional maintenance, consume more energy, and heighten the risk of seed damage. The suctioned seed experiences impact from the seed metering plate during picking, and orifices are not fully sealed after seed pick-up, leading to a need for higher vacuum pressure. Additionally, field vibrations can adversely affect planter performance. To overcome these issues, this study developed a novel flexible orifice seed metering plate and optimised its operating parameters for cotton seed, adopting a central composite rotatable design (CCRD). The plates were developed by adding a layer of elastomeric material on rigid seed metering plate. The experiments were conducted using a developed electronic sticky belt setup in laboratory. An orifice diameter of 3 mm, vacuum pressure of 3.40 kPa, forward speed of 4.67 km/h, extended radius of 1 mm and coating thickness of 0.25 mm were found optimum with a quality feed index of 97.289% and precision index of 4.653%. Minimal difference between laboratory and field performance was noted when operated by an electronic planter. The miss index, multiple index, and precision index obtained under field conditions with rigid seed metering plate were found to be 4.4, 2.8, and 9.08% higher than coated seed metering plate, respectively. A comparatively lower optimal vacuum pressure and higher operation speed was achieved when coated seed metering plate was used in place of rigid seed metering plate. Hence coated seed metering plate can be a low-cost solution to achieve higher speed of precision planting with improved seeding performance.

Article Highlights

A flexible orifice seed metering plate was conceptualized and developed for pneumatic planters.

Flexible orifice seed metering plate was optimized for quality feed index and precision index.

Enhanced performance of developed flexible orifice seed metering plate compared to rigid seed metering plate.

Introduction

Precision planting provides uniform availability of soil nutrients, sunlight, aeration, and water to each plant, resulting in uniform growth and maximum production. It also reduces the economic load on farmer by reducing the input cost for purchase of high value hybrid or genetically modified seeds. Numerous types of precision seed metering mechanisms like vertical plate, horizontal plate, inclined plate, pneumatic, vibratory have been developed. The pneumatic suction type precision seed metering system is more popular for their enhanced field performance and delicate handling of seeds.

A number of research have been carried out in optimisation of machine and operational parameters of pneumatic seed metering plate for precision planting of different seeds. The parameters of a pneumatic seed metering plate were optimised for the metering of cotton seed [1]. Peripheral speed of 0.25 to 0.33 m/s, hole diameter of 2.5 to 3.5 mm, and vacuum pressure of 3 kPa were used to find the optimal value. Singh et al. [2] investigated the performance of a pneumatic cotton planter under different levels of negative pressure from 1 to 2.5 kPa, entry cone angle from 90° to 150°, peripheral speed of the metering disc from 0.29 to 0.69 m/s. Yazgi and Degirmencioglu [3] optimised the seed spacing of a pneumatic precision seeder for cotton seed using CCRD in RSM. Experiments included five levels of hole diameter (1.66, 2.0, 2.5, 3.0, and 3.34 mm), five levels of peripheral speed (0.05, 0.08, 0.12, 0.16, and 0.19 m/s), and five levels of vacuum pressure (2.64, 4, 6, 8, and 9.36 kPa). A vacuum type precision corn planter was optimised using CCRD in RSM [4]. Twenty different combinations of experiments were generated using vacuum pressures of 26.4, 40.0, 60.0, 80.0 and 93.6 mbar, hole diameters of 2.32, 3.0, 4.0, 5.0, and 5.68 mm and peripheral speeds of 0.053, 0.08, 0.12, 0.16, and 0.19 m/s. Yasir et al. [5] designed a pneumatic wheat metering device with 30 holes each of 1.8 mm in diameter. The best combination of vacuum pressure and speed was found using the results of 5 × 5 RCB design with five levels of speed (19, 24, 29, 34, and 39 rpm) and five levels of vacuum pressure (2.5, 3.0, 3.5, 4.0, and 4.5 kPa). A twin vacuum disc metering unit was developed and tested for different crops like corn, cotton, and sunflower [6]. The conditions for best performance were found using the results of CCRD design in RSM. Five levels of hole size (1.66, 2.0, 2.5, 3.0, and 3.34 mm), five levels of peripheral speed (0.52, 0.8, 1.2, 1.6, and 1.87 m/s), and five levels of vacuum pressure (2.64, 4.0, 6.0, 8.0, and 9.36 kPa) were used to perform the experiments for cotton seed.

Investigation regarding different parameters affecting planter performance have been conducted by many researchers. Different physical properties of seeds like kernel density, projected area, sphericity, and thousand kernel mass have a major role to play in the determination of seed metering plate vacuum pressure [7]. Seed holding ratio was found affected by the shape and size of the hole, peripheral velocity, and negative pressure at a 1% level of significance [8]. The highest seed holding ratio was found for oblong holes, followed by circular, triangular, and square. Hole size should be designed on the basis of seed size and seed weight [9, 10]. A mathematical relationship between the physical properties of seed and the vacuum pressure required was established for optimal seed metering [11]. Lu [12] described the airflow through section hole as similar to a small hole jet and hence a chamfered suction hole that could reduce the turbulent loss of air around edge of hole is preferred. Afify et al. [13] developed a mathematical model for the prediction of vacuum pressure requirements in the case of an onion seed metering unit. The reaction force generated on the seed by the seed metering plate during seed pick up was explained. Deng et al. [14] investigated the process of seed sucking in a pneumatic precision metering device for rapeseed and developed mathematical models on contact force and airflow disturbance during the sucking process of seed. The best model was developed by minimising the contact force per point of the contact ring during the seed sucking process. From the produced model, an optimal relationship between the cone angle, the diameter of seed and the diameter of the seed nozzles was established. Pareek et al. [15] found optimal values of orifice size, shape, vacuum pressure, and forward speed for pneumatic seed meter adopting a novel approach where artificial neural network and multi-objective particle swarm optimization were used together. Yazgi and Degirmencioglu [16] optimised vacuum type precision metering of spherical plastic balls with a diameter of 4, 6, 8, and 10 mm. The study concluded that when seed diameter is increased, better speed can be achieved while maintaining desired accuracy. The shape of the seed plate orifice has a considerable effect on its performance and, hence, the orifice shape should be designed according to the shape of the seed [17]. The sucking holes are not completely sealed due to seed shape [18]. Bakhtari and Ahmad [19] designed a vacuum seed metering system for kenaf planting in which they adopted a circular hole with a conical entry. The conical entry is advantageous in closing the sucking hole successfully with one seed so as to avoid multiple sucking [2]. Experiments conducted with a single row vertical disc inside filling seed metering cylinder, the increased missing with increased speed was attributed to insufficient interaction time between the metering hole and seeds within the vacuum zone [20, 21]. Multiple seed picking is encouraged by variation in seed size when the seed is incapable of sealing the sucking hole [22]. It was recommended that the metering plate hole should be made with a conical entrance so as to seal the hole properly with a single seed.

Recent development uses different type of mechanisms to provide better performance while operating at a higher speed. Degirmencioglu et al. [6] developed a twin vacuum disk metering unit in which two metering units are engaged to drop consecutive seed alternatively in one row. Nikolay et al. [23] developed a seed missing prevention system to have improved quality feed index. The system was based on sensing of seed missing by laser receiver and transmitter and regulating speed of seed metering unit using programmed microcontroller and stepper motor. Multiples were avoided in the test by modifying the metering unit as the test was solely carried out for regulation of miss index. The test was carried out with polyoxymethylene spherical balls to avoid effect of variation in seed properties like size, shape, coefficient of friction etc. The obtained result was verified with pea seed. The increased speed to prevent seed missing increased standard deviation. The maximum standard deviation was found to be 1.25 times the set spacing. The maximum tested rotational speed was 25 rpm where up to 2 consecutive seed misses can be avoided and maximum miss index obtained was 0.2%.

The performance of seed metering plate is not only dependent on seed singulation but also on releasing of each seed at exact cut off point. Seed properties like seed mass, size, shape varies seed to seed. Seed dropped under the action of gravity have different releasing as well as dropping position. An air jet seed knockout mechanism for plate type vacuum planters was developed [24]. A decrease in seed damage and an increase in cell filling percentage were reported with the use of the air jet knockout device. Xing et al. [25] developed a new method for the active removal of seed from seed metering plates employing the principle of magnetic repulsion.

Previous studies have highlighted several issues associated with seed metering plates. These include the need for different orifice shapes for different seed shapes, incomplete sealing of orifices leading to multiple seed pickups, chamfering of orifices to improve sealing, inefficient seed picking or missing seeds due to low contact area between the seed and metering plate, significant performance variations caused by seed size, high transmissible field vibrations affecting performance, high reaction forces from the seed metering plate on the seeds, the requirement for separate mechanisms for seed knock-out, and the high cost and complexity of sensor-based or mechanical singulation devices that require skilled setup. Additionally, there is a risk of seed damage in precision planter due to the combined effects of high suction force, rigid seed metering plates, high reaction forces, and assisted mechanical devices.

To address these issues, this study designed and developed a seed metering plate aimed at ensuring a good contact area, completely sealing the orifice after picking the seed, minimizing impact during seed picking, and releasing the seed with positive force at the vacuum pressure cut-off point, regardless of seed size, shape, orientation, and mass. As a cost-effective solution, a flexible orifice was incorporated by coating a rigid seed metering plate with an elastomeric layer. The effects of key parameters on both the rigid and coated seed metering plates were investigated. The plates were optimized for design and operating parameters such as orifice diameter, vacuum pressure, forward speed, extended radius, and thickness in laboratory and evaluated in field conditions for cotton seeds. The performance of both types of plates was compared to assess improvements in the new development.

Materials and methods

Experimental design

Seed properties are essential parameters to consider in the design of seed metering plate. The dimensional, gravimetric, mechanical, and aerodynamic properties were evaluated. The length, width, and thickness of the cotton seed variety (Suraj) used in the experiment were 9.02 ± 0.71, 4.68 ± 0.39, 4.02 ± 0.36 mm respectively. The mass of the seed was 0.0871 ± 0.0134 g, with projected area w.r.t different axis varying from 14.88 ± 2.18 to 33.34 ± 4.59 mm². The orifice of seed metering plate is required to be larger in size to produce a higher suction force on seed. On the other hand, the orifice size is limited to restrict movement of seed into it. To achieve this, 50% and 70% of the seed's geometric mean diameter were calculated. Based on these calculations, an orifice diameter ranging from 2.5 to 3.5 mm was chosen for the study. The suction pressure requirement was determined using the prediction model by Karayel et al., [11], which took into account seed properties [26]. A suction pressure range of 2.5 to 5.5 kPa was selected for the experiment based on calculated result. The operational speed was set between 2.5 and 5.5 km/h, considering the economic conditions of farmers, small and fragmented land holdings, and the average tractor power available in developing countries, which are significant contributors to global cotton production. Developed seed metering plate of diameter 260 mm and PCD of 230 mm with 22 numbers of holes was used for experimentation (Fig. 1).

Fig. 1 [Images not available. See PDF.]

Rigid seed metering plate

The rigid seed metering plate was coated with elastomeric material to create flexible orifice. The conceptual design and different parts are shown in Fig. 2. Natural rubber having good tear resistance, and high elasticity was selected for the purpose. The details of properties of the elastomeric material are given in Table 1. Thin coating can be deflected or compressed by seed kinetic energy when sucked. Therefore, coating thickness was decided to be central value of 0.25 mm with step value of 0.05 mm. The selected thickness were evaluated for deflection through a texture analyser, assuming an applied force as a product of minimum vacuum pressure and maximum orifice area. The flexible area of orifice was varied by reducing or increasing radial extension of coating on rigid orifice. The central value of radial extension was taken as 1 mm with a step value of 0.25 mm. The middle value of extended radius was provided to accommodate minimum projected area of seed.

Fig. 2 [Images not available. See PDF.]

CAD drawing showing details of a rubber coated seed metering plate, a front face of seed metering plate that interacts with seed, b exploded view showing rubber coating on rigid seed metering plate, c back view of seed metering plate, d close view of a flexible orifice, 1-radial extension of rubber coating (E_r), and 2-rigid orifice diameter (D_r)

Table 1. Properties of elastomeric material used for coating

Parameter	Specification
Material name	Natural latex rubber sheet
Finish	Smooth
Durometer (shore A)	35 to 45
Surface treatment	talc
Maximum recommended working temperature	80°C
Tensile strength	25 MPa
Modulus at 500% extension	3 MPa
Breaking initiates at elongation	850%
Tear strength (crescent)	70 N/mm
Hardness (shore micro)	35
Specific gravity	0.95

Response surface methodology (RSM) was employed to investigate the influence of the above independent variables on performance parameters. A central composite rotatable design (CCRD) was chosen as the experimental design as it efficiently predicts nonlinear relationship. The details of independent parameters and it’s levels are given in Table 2.

Table 2. Independent parameters with actual and coded values

(a) Parameters and it’s levels for rigid seed metering plate
		Coded level
		− 1.6817	− 1	0	+ 1	+ 1.6817
Parameter	Step value	Actual level
Orifice diameter (mm)	0.5	2.16	2.5	3	3.5	3.84
Vacuum pressure (kPa)	1.5	1.48	2.5	4	5.5	6.52
Forward speed (km/h)	1.5	1.48	2.5	4	5.5	6.52

(b) Parameters and it’s levels for coated seed metering plate
		Coded level
		− 2.3784	− 1	0	+ 1	+ 2.3784
Parameter	Step value	Actual level
Orifice diameter (mm)	0.5	1.81	2.5	3	3.5	4.19
Vacuum pressure (kPa)	1.5	0.43	2.5	4	5.5	7.57
Forward speed (km/h)	1.5	0.43	2.5	4	5.5	7.57
Extended radius (mm)	0.25	0.40	0.75	1	1.25	1.59
Thickness (mm)	0.05	0.13	0.20	0.25	0.30	0.37

Following CCRD the number of experiments were generated for both rigid as well as flexible orifice seed metering plate. The orifice diameter, vacuum pressure and forward speed were considered for rigid orifice. The extended radius and thickness of coating were added in case of flexible orifice. Twenty and fifty number of experiments, each with five replications was performed in the laboratory for rigid and coated seed metering plates respectively.

Development of seed metering plates

According to the CCRD design the required number of rigid seed metering plates with different orifice diameter and coated seed metering plates with different orifice diameter, extended radius, and coating thickness were developed. The size of rigid orifice was calculated based on orifice diameter and radial extension in Eq. (1) for coated seed metering plates.

1

$$D_r=\left(2,\times ,E_r\right)+O_d$$where, D_r is orifice diameter drilled in the seed metering plate, E_r is radial extension of elastomeric coating towards orifice center, and O_d is orifice diameter provided for seed suction.

Total twenty number of seed metering plates were developed by CNC machining followed by drilling of orifice as per the required rigid orifice diameter. Out of these 20 metering plates, 15 were coated and 5 were rigid seed metering plates. The 15 seed metering plates were coated with different thicknesses of rubber sheet. The coated metering plates were punched to create orifices of the desired size. The punching process was carried out while matching the center of the rigid orifice in coated seed metering plates to the center of the punch. The developed coated seed metering plates are shown in Fig. 3.

Fig. 3 [Images not available. See PDF.]

Developed rubber coated metering plates with different orifice diameter (O_d), extended radius (E_r), and coating thickness (T) (0.13, 0.20, 0.25, 0.30, 0.37 mm for yellow, red, green, blue, and black colored coating respectively)

Laboratory setup

A setup was developed to study the performance of the pneumatic precision planter under simulated conditions in laboratory which is shown in Fig. 4. This facilitates controlling forward speed along with corresponding rotational speed of the seed metering plate and suction pressure. The controlled parameters can be measured and viewed at the same time. A single row unit of the planter was attached to the setup frame. The qualitative performance parameters of the planter were evaluated through the measurement of seed spacing on the sticky belt setup.

Fig. 4 [Images not available. See PDF.]

Developed laboratory setup for experiment. a Front, b top, and c side view

White silicon grease was applied on the flat belt to trap the seed at exact dropped position. The flat belt was attached to a timing belt, which was driven by a timing pulley. The use of timing belt prevents slippage. Hence, an error free measurement of seed spacing corresponding to a desired forward speed was possible. The linear velocity of the belt depends on the rotational speed of the driving pulley. The driving unit consists of 24 V geared DC electric motor (xcluma, MY1016Z3, India), chain and sprocket, driven shaft, and coupler. The PCD of pulley with measured rotational speed was used to calculate linear speed of the conveyor belt. The speed of the motor was varied using a PWM controller.

The rotational speed of seed metering plate corresponding to the set forward speed was calculated. The calculated rotational speed was achieved using VFD control (Excella electronics, India) of the 5 hp, 3 phase induction motor (Excella electronics, India) driving the seed metering plate. The vacuum pressure was generated using a BLDC motor driven high rotational speed aspirator (Wonsmart, WS9290-12–220-S200, China). This blower was attached to the vacuum chamber of the pneumatic seed metering unit. The BLDC motor was operated using a driver (Wonsmart, WS1230DY04V01-SRP004, China). The driver was provided with a knob to control the supplied voltage and regulate rotational speed. The suction pressure can be maintained using this knob. A pressure gauge (Lutron, VC-9200, Taiwan) sensor was inserted between the aspirator and vacuum chamber of the seed metering unit for simultaneous measurement of vacuum pressure. Vacuum pressure can be seen on the display of the pressure gauge.

Calculation of indices and optimisation

Based on the measured seed spacing the miss index, multiple index and precision index were calculated for each run using Eqs. (2–4) [2, 5]. The quality feed index was calculated using Eq. 5. It is related to miss and multiple index and hence was not calculated for each experimental run. However, it was used for comparing the obtained result when miss and multiple index were combinedly addressed.

2

$$\text{MII}=\frac{{\text{n}}_1}{\text{N}}$$

3

$$\text{MUI}=\frac{{\text{n}}_2}{\text{N}}$$

4

$$\text{PI}=\frac{{\text{S}}_{\text{d}}}{\text{S}}$$

5

$$\text{QFI}=100-(\text{MII}+\text{MUI})$$where, MII is the miss index, MUI is the multiple index, PI is the precision index, n₁ is the number of seed spacings more than 1.5 times the set spacing, n₂ is number of the seed spacings less than 0.5 times the set spacing, N is the total number of the seed spacings, S_d is the standard deviation of the seed spacings that are excluded under the miss index and multiple index calculations, S is the set spacing, and QFI is quality feed index.

The obtained results corresponding to each combination of independent parameter were used to determine the optimal value through numerical optimisation in design expert software. The criteria for optimisation were set to minimise all the dependent parameters while varying all independent parameters in the range except the forward speed which was set to maximise. The optimised independent parameters and corresponding predicted values of responses were obtained in the first stage of optimisation. The nearest easily manufacturable orifice size, thickness and extended radius values were targeted in the next stage optimization. Consequently, different optimum vacuum pressure and peripheral velocity values were obtained. The desirability was calculated following Box and Draper [27] to know the performance of optimisation, where 0 indicates completely undesirable and 1 indicates completely desirable.

Field evaluation

The research field of CIAE, Bhopal (23.3099° N, 77.4031° E) was used for the study. The soil is black cotton soil. The field was prepared by primary and secondary tillage operations by mouldboard plough and rotavator, respectively. Soil properties like moisture content and bulk density were obtained. The field performance was measured in the month of June, 2022. The optimized rigid and coated seed metering plates were used in a developed electronic planter.

The developed planter was run in the field at optimal forward speed with a set seed to seed spacing of 0.15 m. The depth of planting was adjusted to 10 mm so that the seed remains partially uncovered. This helped in easy and accurate measuring of seed to seed spacing. The optimal levels of independent parameters were maintained. Readings were taken for five replications each covering a length of 7.5 m. The spacing was measured using a steel ruler of one meter length and noted down. The measured spacings were later analyzed to find out the miss index, multiple index, and precision index using Eqs. (2–4).

Results and discussion

The rigid seed metering plate was optimised based on the data obtained from laboratory experiments. A similar procedure described for coated seed metering plate was applied for rigid seed metering plate. The optimised parameters were used to evaluate rigid seed metering plate in the laboratory and field conditions. These data are helpful for comparison of the coated seed metering plate with conventional rigid seed metering plate. The results obtained from experiments and analysis for coated seed metering plate was detailly presented and discussed in this section.

Results from laboratory experiments

The miss index, multiple index and precision index obtained from the laboratory study at different orifice diameter, vacuum pressure, forward speed, extended radius and thickness are presented in Table 3. The miss index, multiple index, and precision index were found varying between 0 to 14%, 0 to 18%, and 3.72 to 14% at different combinations of the levels of independent parameters. Quadratic polynomial equations were developed through ANOVA for each depended parameters. The effect of each independent parameter and the interaction effect of two independent parameters on each dependent parameter were found out from the ANOVA for rigid and coated seed metering plates.

Table 3. Performance of coated seed metering plate obtained in different experimental runs

Independent parameters					Dependent parameters
Orifice diameter (mm)	Vacuum pressure (kPa)	Forward speed (km/h)	Extended radius (mm)	Thickness (mm)	Miss index (%)	Multiple index (%)	Precision index (%)
2.50	5.50	5.50	1.25	0.30	2	5	9.95
2.50	2.50	5.50	0.75	0.30	10	0	9.60
2.50	2.50	5.50	1.25	0.20	9	0	6.60
3.50	2.50	5.50	0.75	0.20	4	0	10.30
3.50	5.50	5.50	0.75	0.30	1	8	14.00
3.00	4.00	4.00	1.00	0.25	0	3	4.04
3.00	4.00	4.00	1.00	0.37	1	0	10.50
3.50	5.50	2.50	0.75	0.30	1	12	10.90
2.50	2.50	2.50	0.75	0.20	7	0	6.75
3.50	5.50	2.50	0.75	0.20	2	14	8.90
2.50	5.50	2.50	0.75	0.30	2	4	8.20
2.50	5.50	2.50	0.75	0.20	3	6	6.20
2.50	5.50	5.50	1.25	0.20	2	8	7.95
3.00	4.00	4.00	1.59	0.25	0	3	9.00
3.50	5.50	5.50	1.25	0.30	0	13	13.00
3.00	4.00	4.00	1.00	0.25	0	3	4.10
3.00	4.00	4.00	0.40	0.25	2	0	12.00
2.50	5.50	2.50	1.25	0.30	1	7	7.20
3.50	2.50	2.50	1.25	0.20	2	1	8.10
3.50	2.50	2.50	0.75	0.30	2	0	11.10
1.81	4.00	4.00	1.00	0.25	14	0	3.72
3.50	5.50	2.50	1.25	0.30	0	15	9.90
3.50	5.50	2.50	1.25	0.20	1	17	7.90
3.00	4.00	4.00	1.00	0.25	0	3	4.02
3.00	4.00	4.00	1.00	0.13	2	6	6.00
2.50	5.50	2.50	1.25	0.20	2	9	5.20
2.50	5.50	5.50	0.75	0.30	2	3	10.95
3.50	2.50	5.50	1.25	0.20	2	0	9.30
2.50	2.50	2.50	1.25	0.20	6	0	5.75
3.00	4.00	4.00	1.00	0.25	0	3	4.05
3.00	4.00	0.43	1.00	0.25	0	3	6.34
3.50	5.50	5.50	0.75	0.20	2	12	12.00
2.50	2.50	5.50	1.25	0.30	7	0	8.60
3.00	4.00	7.57	1.00	0.25	0	3	12.00
2.50	5.50	5.50	0.75	0.20	3	5	8.95
3.50	2.50	2.50	0.75	0.20	3	0	9.10
3.50	2.50	5.50	1.25	0.30	1	0	12.86
3.50	5.50	5.50	1.25	0.20	1	16	11.00
3.00	4.00	4.00	1.00	0.25	0	3	3.95
2.50	2.50	2.50	1.25	0.30	5	0	7.75
3.00	7.57	4.00	1.00	0.25	0	18	6.16
3.00	4.00	4.00	1.00	0.25	0	3	3.98
3.50	2.50	2.50	1.25	0.30	1	0	10.10
2.50	2.50	5.50	0.75	0.20	9	0	7.60
3.00	4.00	4.00	1.00	0.25	0	3	4.08
3.50	2.50	5.50	0.75	0.30	2	0	12.30
4.19	4.00	4.00	1.00	0.25	0	14	9.58
2.50	2.50	2.50	0.75	0.30	6	0	8.75
3.00	0.43	4.00	1.00	0.25	13	0	4.96
3.00	4.00	4.00	1.00	0.25	0	3	3.97

Effect of independent parameters on performance of coated seed metering plate

A clear understanding of the effect of different independent parameters on the miss index, multiple index, and precision index of coated seed metering plate can be visualised from the 3-D graphs presented in Figs. 5, 6, 7.

Fig. 5 [Images not available. See PDF.]

Effect of independent parameters on miss index. a Interaction effect of orifice diameter and vacuum pressure, b effect of extended radius, and c effect of thickness

Fig. 6 [Images not available. See PDF.]

Effect of independents parameters on multiple index. a Effect of orifice diameter and vacuum pressure, b effect of forward speed and vacuum pressure, c effect of extended radius and vacuum pressure, and d effect of thickness and vacuum pressure

Fig. 7 [Images not available. See PDF.]

Effect of independents parameters on precision index. a Effect of forward speed and vacuum pressure, b effect of orifice diameter, c effect of extended radius, and d effect of thickness

The miss index was affected by orifice diameter, vacuum pressure, and extended radius at 1% level of significance, while it was affected by thickness at 5% level of significance. Similarly, the interaction of orifice diameter and vacuum pressure was found to affect the miss index at 1% level of significance. The square terms of orifice diameter and vacuum pressure were also observed to affect the miss index at 1% level of significance. Orifice diameter and vacuum pressure affected the miss index in a similar manner as in the case of rigid seed metering plates, but the value of the miss index was found to be lower here. A decrease in miss index was observed with the increase of extended radius. The rubber coat is layered on the rigid seed metering plate. A greater extended radius of coating towards orifice center makes the orifice completely of coated material, which is flexible in nature. When the seed interacts with the completely flexible orifice, a negligible amount of reaction force is generated as the impact force converts to orifice deflection. Along with this low reaction force, higher deflection provides a better area of contact with seeds, causing a lower missing of seeds at pick up. The increase in coating thickness reduces the miss index. A small increase in miss index was observed when the coating thickness was very low. This could be attributed to the low likelihood of very small seeds clogging an orifice. When the coating is very thin, seeds of very small size partially enter the orifice, compressing the periphery of the coating radially outward. Forward speed was not affecting the miss index at 5% level of significance. Although the seed and seed metering plate interaction time is reduced at higher speeds, the coated seed metering plate was found to pick single seeds at the higher speeds of the experiment. The coated seed metering plate had a flexible orifice that deflected inward, outward, or radially with applied forces. The coated seed metering plate has a high coefficient of friction, a high contact area, and a low coefficient of restitution between seed and seed metering plate. These properties of the coated seed metering plate help with easy picking of seed. A single seed is chosen that is closest to the orifice, has the most area exposed toward the orifice, and has the least restrictive forces. A higher amount of time is provided to seed to obtain the velocity of the seed metering plate as the coated rubber extends and compresses radially. The acceleration requirement reduces as the transition period of velocity increases. The seed gains velocity gradually, and the radial tension and compression of the rubber coat decrease to zero. Therefore, coated seed metering plates also have better performance at higher speeds of operation.

The multiple index was revealed to be influenced by orifice diameter, vacuum pressure, extended radius, and thickness at 1% level of significance. Forward speed was found to affect it at 5% level of significance. Orifice diameter and vacuum pressure affected the multiple index in a similar manner as in the case of a rigid seed metering plate, but the value of the multiple index was found lower here. An increase in extended radius was found, increasing the multiple index. The rubber coat is layered on the rigid seed metering plate. A higher extended radius of coating towards orifice center makes the orifice completely of coated material which is flexible in nature. When the seed interacts with the completely flexible orifice, a negligible amount of reaction force is generated as the impact force converts to orifice deflection. Along with this low reaction force, higher deflection provides a better area of contact with seeds, causing a higher number of multiple pick up. The increase in coating thickness reduces the multiple index. A thicker coating needs higher suction force to be compressed. The lower deflection of the coating causes a relatively higher reaction force and lower contact area between the seed metering plate and seed. Multiple picking is reduced as a result of these changes in seed picking characteristics. A reduced multiple index was found at higher forward speeds. This may be because of the reduced interaction time between seed and the seed metering plate. Hence, only a single seed that is majorly affected by the pressure at the orifice is picked.

The interaction effect of orifice diameter and vacuum pressure was observed to affect multiple index at 1% level of significance, as with rigid seed metering plate. The interaction effect of forward speed and vacuum pressure on multiple index was observed significant (p ≤ 0.05). Increased vacuum pressure significantly overcomes the reduction in multiple index caused by increasing forward speed. Similarly, a decrease in multiple index due to a decrease in vacuum pressure may be balanced by decreasing speed. The interaction effect of radial extension and vacuum pressure was observed, affecting multiple index at 1% level of significance. Increasing vacuum pressure was found to be increasing multiple index and increasing radial extension was also observed to be increasing multiple index. Increasing one while decreasing another may have a balancing effect as the interaction is significant. The interaction effect of thickness and vacuum pressure was observed, affecting multiple index at 1% level of significance. Reduction in thickness was observed to increase multiple index while reduction in vacuum pressure was seen to reduce multiple index. Decreasing or increasing value of both the parameters may have a balancing effect as interaction is significant.

The precision index was found to be affected by orifice diameter, forward speed, extended radius, and thickness at 1% level of significance. Orifice diameter affected the precision index in a similar manner as in rigid seed metering plates, but the value of the precision index obtained is lower here. The lower precision index indicates a lower change in seed spacing than the set spacing. The lower change in seed spacing may be attributed to the positive dropping of seeds exactly at the vacuum cutoff. The flexible orifice in the coated seed metering plate deflects inward at the time of seed suction and comes back to its position as the vacuum is cut off. The lowest precision index was obtained in between the lowest and highest forward speed. The higher precision index obtained at lower forward speed may be explained as lower positive force generated by the slower release of the inward deflected flexible orifice as time taken in movement of seed metering plate from suction zone to vacuum pressure cutoff zone is higher at lower peripheral speed. The precision index was found to be decreasing and then increasing with an increase in extended radius. A very low extended radius has a low inward deflection and seed to seed metering plate contact area during seed picking. When the orifice returns to its normal position, a lower magnitude of positive force is applied to the seed. Though the seed contact area is low and it helps with early detachment of seed at cutoff, the positive force plays a major role. Hence, with a very low extended radius, the seed spacing differs more, resulting in a higher precision index. A large extended radius results in a larger contact area. The effect of contact area dominates over the effect of positive force due to deflection, resulting in a higher precision index. The precision index did not change with the initial increase in coating thickness but started increasing near its central value. The deflection of coating was sufficient for positive dropping of the seed during the initial increase, but as thickness increased, the reduced deflection of coating became inefficient for positive dropping of seed at the cutoff. This results in an increased precision index with increased thickness.

The interaction of vacuum pressure and forward speed was found to affect the precision index at 1% level of significance. This indicates the effect of vacuum pressure on precision index can be significantly lowered or increased by a change in the value of forward speed or vice versa. The square terms of orifice diameter, vacuum pressure, forward speed, extended radius, and thickness were also observed affecting the precision index at 1% level of significance.

Optimisation and field evaluation

The optimised values and corresponding predicted values of parameters are presented in Table 4. Although a 3 mm orifice size was found optimal for both rigid and coated seed metering plate, a lower vacuum pressure of 3.401 kPa and higher speed of 4.668 km/h was optimal for coated seed metering plate than respective value of 3.737 kPa and 4.222 km/h in case of rigid seed metering plate. The predicted miss, multiple, and precision indices were 2.291, 3.843, 8.309% for rigid seed metering plate while 1.162,1.549, 4.653% for coated seed metering plate respectively.

Table 4. Optimized values of independent parameters and predicted values of corresponding dependent parameters

Type of seed metering plate	Od (mm)	Vp (kPa)	Fs (km/h)	Er (mm)	T (mm)	MII (%)	MUI (%)	PI (%)	Desirability (%)
Rigid	3.000	3.737	4.222			2.291	3.843	8.309	0.859
Coated	3.000	3.401	4.668	1.000	0.250	1.162	1.549	4.653	0.916

The laboratory experiment was again conducted with the optimum values of orifice size, vacuum pressure and forward speed. In addition to these parameters optimum values of extended radius and thickness were used in case of coated seed metering plate. Five replications were done. The obtained result is presented in Table 5.

Table 5. Laboratory performance indices obtained using two types of metering plates

Type of seed metering plate	MII (%)	MUI (%)	PI (%)
Rigid	2.00	4.00	8.57
Coated	1.00	2.00	4.96

The optimized seed metering plate was run with optimum operational parameters in prepared field as described in Sect. 2.5. Field evaluation of developed seed metering plate is shown in Fig. 8 and the obtained results are presented in Table 6.

Fig. 8 [Images not available. See PDF.]

Field evaluation of coated seed metering plate. a Developed electronic planter with coated seed metering plate in prepared field, b coated seed metering plate during operation, c developed electronic planter with rigid seed metering plate, d rigid seed metering plate during operation

Table 6. Field performance Indices obtained using two types of metering plates

Type of seed metering plate	MII (%)	MUI (%)	PI (%)
Rigid	5.6	4.8	14.21
Coated	1.2	2.0	5.13

Comparison of rigid and coated seed metering plates under laboratory and field conditions

A higher difference in value between laboratory and field performance indices was observed in the case of rigid seed metering plates than coated seed metering plates. All values of performance indices under both studies were found to be lower when planted with coated seed metering plates than with rigid seed metering plates. This indicates a better performance of coated seed metering plates than rigid seed metering plates. A Tukey test was used to compare the obtained results more effectively, which is graphically presented in Fig. 9.

Fig. 9 [Images not available. See PDF.]

Comparison of planting performance. a Miss index, b multiple index, and c precision index observed in laboratory and field experiments conducted at optimized parameters using rigid and coated seed metering plates. LR, Laboratory experiment conducted with rigid seed metering plate; LC, Laboratory experiment conducted with coated seed metering plate; FR, Field experiment conducted with rigid seed metering plate; and FC,  Field experiment conducted with coated seed metering plate

The planter moves at the optimal forward speed on the undulated surface of the field. Thus, the seed and seed metering plates are subjected to inertia due to forward motion and vertical vibration. This affects planter performance in the field, and a difference in performance between laboratory and field is seen. Because the transmissibility is greater in the case of a rigid seed metering plate, the above-mentioned additional forces can have a greater impact. The transmissibility of coated seed metering plate decreases as the radially extended part of the rubber coating at the orifice acts as a shock absorber. As a result, the seed is less affected and the performance does not differ as much.

The miss index obtained under laboratory condition with rigid seed metering plate was found 1% higher than coated seed metering plate. The miss index obtained under field conditions with rigid seed metering plate was found to be 4.4% higher than coated seed metering plate. The reduced miss index was due to a higher contact area as coating is deflected inward, a higher coefficient of friction, and a lower coefficient of restitution between rubber coating and seed. The radial deflection of flexible orifice enables picking of seeds at high speed as described earlier.

The multiple index obtained under laboratory conditions with rigid seed metering plate was 2% higher than coated seed metering plate. The multiple index obtained under field conditions with a rigid seed metering plate was found to be 2.8% higher than a coated seed metering plate. The decreased multiple index of a coated seed metering plate is because of its sealing characteristics. Proper contact between coating and seed seals the orifice completely and thereby avoids the picking of more seed through the same orifice.

The precision index obtained under laboratory conditions with rigid seed metering plate was found 3.61% higher as compared to coated seed metering plate. The precision index obtained under field conditions with rigid seed metering plate was found to be 9.07% higher than coated seed metering plate. Because seed was released precisely at the vacuum cutoff point, coated seed metering plates showed a lower precision index. This positive dropping of seeds is performed by the movement of an inwardly deflected orifice to its position as the vacuum pressure is cut off.

In addition to the above points, the coated seed metering plate was found to be requiring 8.99% less vacuum pressure than rigid seed metering plate. Hence, the coated seed metering plate is more energy efficient. The high coefficient of friction, higher area of contact, and lower coefficient of restitution between coating and seed are some of the reasons behind its efficient working. Each orifice is completely sealed as the coating is pulled inward at the time of seed pickup. Sealing of each orifice reduces pressure loss. The deflected coating comes back to its normal position at vacuum cutoff, which releases the seed at the exact time. Thus, the energy saved during the seed pickup process through coating deflection, which also avoids the impact reaction force on seed, is utilised for positive dropping of seed.

Several researchers reported the occurrence of seed damage in pneumatic planter (Yasir et al. [5], Barut and Ozmerzi [8], and Karayel et al. [11]). The coated seed metering plate reduces the impact on seed and helps in smooth handling. Mechanical seed singulator/ cutoff as well as seed knock out devices are not required in coated seed metering plate. Thus, there may be reduced seed damage when coated seed metering plates are used compared to rigid seed metering plates. Prabhakaran et al. [28] discussed regarding relationship between properties of rubber and grain breakage in a rubber roll sheller. Post investigation on grain damage by threshing drum, application of rubber coating was suggested [29]. Reduction in breakage was observed by application of elastomer (EPDM) based flexible threshing system [30].

The addition of seed cutoff, knockout devices, or sensor-based singulation systems increases the price, whereas the total cost of elastomeric coating was Rs. 250 per metering plate and is expected to be further reduced when produced on an industrial scale. The reduced number of parts and eradication of complex mechanism increases the reliability of operation and reduces initial as well as maintenance cost. The comparison of coated seed metering plate demonstrated higher precision in seeding than a rigid seed metering plate. It can adopt the seed shape and size, providing a high contact area. It also seals the orifice completely. So, a unique orifice shape and size may not be necessary for seeds of different crops, but varying suction forces are required. Future studies in the aspect are suggested, where common flexible orifice seed metering plates may be developed for seeds divided into different classes, like small, medium, and large, for precision sowing through vacuum pressure adjustment. Computer simulation based experimental runs and application of ANN optimization techniques can be used as effective way to further explore and validate advantages of this flexible orifice seed metering plates for pneumatic planter.

Conclusion

The following conclusions have been drawn from the study:

1. The orifice diameter, vacuum pressure, extended radius, thickness, and interaction of the orifice diameter and vacuum pressure were found to influence the miss index on a coated seed metering plate. The miss index obtained under optimized laboratory condition with rigid seed metering plate was found 1% higher than coated seed metering plate. A reduced miss index was obtained with an increase in extension radius and thickness.

2. The orifice diameter, vacuum pressure, extended radius, thickness, and forward speed were found to influence the multiple index on a coated seed metering plate. The multiple index obtained under optimized laboratory conditions with rigid seed metering plate was 2% higher than coated seed metering plate. An increased multiple index was obtained with an increase in extension radius while it reduced with increased thickness and forward speed. The interaction effects of vacuum pressure and orifice diameter, vacuum pressure and forward speed, vacuum pressure and extended radius, and vacuum pressure and thickness were also found to be significantly affecting the multiple index.

3. The precision index in coated seed metering plate was found to be influenced by orifice diameter, forward speed, extended radius, and thickness. The interaction effect of forward speed and vacuum pressure affected the precision index. The precision index obtained under laboratory conditions with rigid seed metering plate was found 3.61% higher as compared to coated seed metering plate. The lower precision index in coated seed metering plate was due to the positive release of seed exactly at cutoff caused by the movement of the inwardly deflected coating to its normal position.

4. The optimum vacuum pressure and forward speed were obtained for an orifice diameter of 3 mm, a vacuum pressure of 3.40 kPa, a forward speed of 4.67 km/h, an extended radius of 1 mm, and a thickness of 0.25 mm.

5. The optimized vacuum pressure in case of coated seed metering plate was found 8.99% lower than rigid seed metering plate. The lower vacuum pressure required was attributed to proper sealing of orifice, better contact area between seed and orifice, higher coefficient of friction, and lower reaction force from the orifice acting against seed picking.

6. The optimized forward speed in case of coated seed metering plates was found 10.56% higher than rigid seed metering plate. The radial contraction and extension of flexible orifice, provided higher time to the picked seed to reach the required higher peripheral speed at which the seed metering plate was rotated. This enabled the planter to achieve a better optimal speed of operation.

7. At optimized conditions, the quality feed index and precision index of 97.289 and 4.653% were observed from laboratory tests for coated seed metering plates while it was seen to be 93.866 and 8.309% for rigid seed metering plates. Similarly, a quality feed index and precision index of 96.8 and 5.13% were obtained from a field test while using coated seed metering plates at optimised conditions while it was seen to be 89.6 and 14.21% using rigid seed metering plates at optimised conditions.

8. The miss index, multiple index, and precision index obtained under field conditions with rigid seed metering plate were found to be 4.4%, 2.8%, and 9.08% higher than coated seed metering plate, respectively. Any rigid seed metering plate can be improved for pneumatic precision planting by adopting this invention.

Acknowledgements

The authors acknowledge help and support obtained from Director, Central Institute of Agricultural Engineering, Bhopal, India and Director, Central Institute for Cotton Research, Nagpur, India.

Author contributions

Conceptualization, review, experimentation, original draft preparation [Jyotirmay Mahapatra]; project administration and supervision [Prem Shanker Tiwari]; writing—review and editing [Krishna Pratap Singh]; formal analysis and resources [Balaji Murhari Nandede]; contribution in conduction of experiments [Jagjeet Singh]; manuscript review and corrections [Ramesh K. Sahni]. All authors read and approved the final manuscript.

Funding

The research is supported by ICAR- Central Institute of Agricultural Engineering, Bhopal and Indian Agricultural Research Institute, New Delhi.

Data availability

The analyzed datasets are available from the corresponding author on reasonable request.

Code availability

Not applicable.

Declarations

Competing interests

The authors declare no competing interests.

Abbreviations

3-D

Three dimensional

ANOVA

Analysis of variance

BLDC

Brushless direct current

CAD

Computer aided design

CCRD

Central composite rotatable design

CIAE

Central Institute of Agricultural Engineering

CNC

Computerised numerical control

DC

Direct current

EPDM

Ethylene Propylene Diene Monomer

GMD

Geometric mean diameter

hp

Horse power

ha

Hectares

km/h

Kilometer per hour

kPa

Kilo Pascal

mm

Milli meter

MII

Miss index

MUI

Multiple index

m/s

Meter per second

PCD

Pitch circle diameter

PI

Precision index

Ph

Phase

PWM

Pulse width modulation

QFI

Quality feed index

R²

Coefficient of determination

RCB

Randomised complete block

rpm

Revolution per minute

RSM

Response surface method

VFD

Variable frequency drive

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

1. Panning, JW; Kocher, MF; Smith, JA; Kachman, SD. Laboratory and field testing of seed spacing uniformity for sugarbeet planters. Appl Eng Agric; 2000; 16, 1 pp. 7-13. [DOI: https://dx.doi.org/10.13031/2013.4985]

2. Singh, RC; Singh, G; Saraswat, DC. Optimisation of design and operational parameters of a pneumatic seed metering device for planting cottonseeds. Biosys Eng; 2005; 92, 4 pp. 429-438. [DOI: https://dx.doi.org/10.1016/j.biosystemseng.2005.07.002]

3. Yazgi, A; Degirmencioglu, A. Optimisation of the seed spacing uniformity performance of a vacuum-type precision seeder using response surface methodology. Biosys Eng; 2007; 97, 3 pp. 347-356. [DOI: https://dx.doi.org/10.1016/j.biosystemseng.2007.03.013]

4. Yazgi, A; Değirmencioğlu, A; İsmet, ÖN; Bayram, E. Mathematical modelling and optimization of the performance of a metering unit for precision corn seeding. Tarım Makinaları Bilimi Dergisi; 2010; 6, 2 pp. 107-113.

5. Yasir, SH; Liao, Q; Yu, J; He, D. Design and test of a pneumatic precision metering device for wheat. Agric Eng Int CIGR J; 2012; 14, 1 pp. 16-25.

6. Değirmencioğlu, A; Çakmak, B; Yazgi, A. Prototype twin vacuum disk metering unit for improved seed spacing uniformity performance at high forward speeds. Turk J Agric For; 2018; 42, 3 pp. 195-206. [DOI: https://dx.doi.org/10.3906/tar-1708-71]

7. Barut ZB. Farkli tohumlarin ekiminde kullanilan d.uusey plakali, hava emisli hassas ekici d.uuzenin uygun -calisma kosullarinin saptanmasi. Determination of the optimum working parameters of a precision vacuum seeder. PhD Thesis, University of Cukurova, Adana, Turkey. 1996.

8. Barut, ZB; Özmerzi, A. Effect of different operating parameters on seed holding in the single seed metering unit of a pneumatic planter. Turk J Agric For.; 2004; 28, 6 pp. 435-41.

9. Scrödl J. Einzelkornsamaschinen DLG-Prüfberichte- Sammelband. DLG, Zimmeweg 16, Frankfurt/Main, 1977.

10. Zehetner, H; Hammerschmid, B. Welche Factoren Beeinflussen die Ablagegenauigkeit von Einzelkornsamaschinen bei Maissaat. Practische Landtechnik; 1984; 4, pp. 128-130.

11. Karayel, D; Barut, ZB; Özmerzi, A. Mathematical modelling of vacuum pressure on a precision seeder. Biosys Eng; 2004; 87, 4 pp. 437-444. [DOI: https://dx.doi.org/10.1016/j.biosystemseng.2004.01.011]

12. Lu, HQ. Jet technology theory and its application; 2004; Wuhan, Wuhan University Press: in Chinese

13. Afify, MT; El-Haddad, ZA; Hassan, GE; Shaaban, YA. Mathematical model for predicting vacuum pressure of onion seeds precision seeder. Misr J Agric Eng; 2009; 26, 4 pp. 1776-1799. [DOI: https://dx.doi.org/10.21608/mjae.2009.107382]

14. Deng, X; Li, X; Shu, C; Huang, H; Liao, Q. Mathematical model and optimization of structure and operating parameters of pneumatic precision metering device for rapeseed. J Food Agric Environ.; 2010; 8, 3/4 part 1 pp. 318-22.

15. Pareek, CM; Tewari, VK; Machavaram, R. Multi-objective optimization of seeding performance of a pneumatic precision seed metering device using integrated ANN-MOPSO approach. Eng Appl Artif Intell; 2023; 117, [DOI: https://dx.doi.org/10.1016/j.engappai.2022.105559]

16. Yazgi, A; Değirmencioğlu, A. Optimization of the seed spacing uniformity of a vacuum type precision seeder using spherical materials. Ege Üniv Ziraat Fakültesi Dergisi; 2015; 52, 3 pp. 277-286. [DOI: https://dx.doi.org/10.20289/euzfd.48916]

17. Anisa, G. Optimization of the shape and size of seed plate orifice for accurate single seed planting of the crops. Int J Agric Eng; 2017; 10, 1 pp. 31-36. [DOI: https://dx.doi.org/10.15740/HAS/IJAE/10.1/31-36]

18. Xing, H; Wang, Z; Luo, X; He, S; Zang, Y. Mechanism modeling and experimental analysis of seed throwing with rice pneumatic seed metering device with adjustable seeding rate. Comput Electron Agric; 2020; 178, [DOI: https://dx.doi.org/10.1016/j.compag.2020.105697]

19. Bakhtiari, MR; Ahmad, D. Design of a vacuum seed metering system for kenaf planting. Agric Eng Int CIGR J; 2017; 19, 3 23.

20. Liao, Q; Li, J; Qin, G. Simulation analysis on air current field of pneumatic precision metering device for rapeseed. Nongye Jixie Xuebao.; 2009; 40, 7 pp. 78-82.

21. Yitao, L; Lei, W; Qingxi, L. Design and test of an inside-filling pneumatic precision centralized seed-metering device for rapeseed. Int J Agric Biol Eng; 2017; 10, 2 pp. 56-62. [DOI: https://dx.doi.org/10.25165/IJABE.V10I2.2061]

22. Ibrahim, EJ; Liao, Q; Wang, L; Liao, Y; Yao, L. Design and experiment of multi-row pneumatic precision metering device for rapeseed. Int J Agric Biol Eng; 2018; 11, 5 pp. 116-123. [DOI: https://dx.doi.org/10.25165/IJABE.V11I5.3544]

23. Nikolay, Z; Nikolay, K; Gao, X; Li, QW; Mi, GP; Huang, YX. Design and testing of novel seed miss prevention system for single seed precision metering devices. Comput Electron Agric; 2022; 198, [DOI: https://dx.doi.org/10.1016/j.compag.2022.107048]

24. Dizaji, HZ; Taheri, MR; Minaei, S. Air-jet seed knockout device for pneumatic precision planters. AMA Agric Mech Asia Afr Latin Am; 2010; 41, 1 pp. 45-50.

25. Xing, H; Wang, Z; Luo, X; Zang, Y; Yang, W; Zhang, M; Ma, Y. Design of an active seed throwing and cleaning unit for pneumatic rice seed metering device. Int J Agric Biol Eng; 2018; 11, 2 pp. 62-69. [DOI: https://dx.doi.org/10.25165/j.ijabe.20181102.3844]

26. Mahapatra, J; Tiwari, PS; Singh, KP; Nandede, BM; Babu, VB; Singh, K. Analysis of cotton (Gossypiumhirsutum) seed properties for engineering applications. Curr Adv Agric Sci; 2022; 14, 1 pp. 27-33. [DOI: https://dx.doi.org/10.5958/2394-4471.2022.00005.3]

27. Box, GE; Draper, NR. Empirical model-building and response surfaces; 1987; Hoboken, Wiley:

28. Prabhakaran, P; Ranganathan, R; Muthu Kumar, V; Rajasekar, R; Devakumar, L; Pal, SK. Review on parameters influencing the rice breakage and rubber roll wear in sheller. Arch Metall Mater; 2017; 62, 3 pp. 1875-1880. [DOI: https://dx.doi.org/10.1515/amm-2017-0284]

29. Qabaradin, A; Tsegaye, A. A evaluation of soybean thresher for chickpea crop. Irish Interdiscip J Sci Res; 2021; 5, 2 pp. 101-8.

30. Li, Y; Fan, H; Xu, Y; Jiang, J; Cui, T; Su, Y; Qiao, M; Han, S; Qian, J. Decreasing grain processing breakage with a novel flexible threshing system: multivariate optimization and wear investigation. J Food Process Preserv; 2022; 46, 8 [DOI: https://dx.doi.org/10.1111/jfpp.16794]