Introduction

Garlic is a major spice vegetable cultivated in the area around 1,419,023 ha in all over the world not only in Korea but also in China, India, and Bangladesh.

Garlic cultivation areas by countries are 834,825 ha in China occupying 49% of the total world cultivation area followed by India in 408,560 ha and Bangladesh in 71,706 ha. Korea ranks at sixth with its garlic cultivation area 24,700 ha in 2023 (FAO, 2025). Garlic cultivation mode in Korea is roughly divided into southern-type and northern-type. In the southern-type garlic cultivation, garlic sprouts in the planting year and is harvested in the next year after passing winter season. Northern-type cultivation is to make garlic sprout in the next year and harvested after passing winter without having a sprout in the planting year.

In Korea, southern-type garlic cultivation occupies 81% of the total garlic cultivation areas depending on the cultivation conditions such as weather suitable for the garlic cultivation, field size, and soil type etc. The cultivation mode is mostly by plastic film mulching in most of the garlic cultivation areas since vinyl mulching practice has merits of keeping the soil warm, retaining moisture in the soil, and restricting weed growth (Choi et al., 2008).

Cultivation stage of southern-type garlic is comprised of plowing and harrowing, ridge formation, vinyl mulching, manual planting, cultivation management, and harvesting. Among these series of works, mechanization has been completed for the plowing and harrowing, ridge formation, and harvest.

For the northern-type garlic, mechanization of the garlic clove planting work which takes around 18~23.4% of labor among the works for the garlic cultivation has been progressed much by developing a mechanical garlic planter attached to the power tiller.

However, for the southern-type garlic, vinyl having holes is covered over the ridge and one garlic clove is planted one by one manually. The mechanization in place of laborious garlic clove planting is, therefore a dire need.

Many researchers have been devoted in the mechanization of garlic clove planting till date as Iwasaki et al. (1993, 1995) have investigated the furrow opening shape, clove laying condition, and relation with draft resistance of the furrow opener and soil moisture contents to develop a garlic planter on the field having high sand contents. They also conducted a field trial with the developed semi-automatic tractor-attached six-row bucket garlic planter in which garlic clove was manually supplied. They reported to have achieved the work efficiency enhancement by 50% as against conventional labor intensity garlic planting work as well as more even planting interval and depth than those of conventional manual planting.

Park et al. (2000) have conducted a field experiment with a bucket-type 12-row garlic planter attached to the tractor for the northern-type garlic and reported to have achieved the work efficiency of 6.3 hours/ha that was 48 times more efficient than manual planting. Jarudchai et al. (2002) also conducted an experiment with the developed garlic planter on which a vertical metering plate and a triangular hopper were combined. A bucket-type garlic planter was also tested in their experiment. They reported that the bucket-type garlic planter showed the best seed metering performance with a very low garlic clove damage rate 0.23%. Garg and Dixit (2003) have reported field test results with one-row type manual garlic planter comprised of metering device, hopper, and driving part. The work efficiency of 0.03~0.04 ha per hour was achieved enabling the garlic clove planting cost reduction by 15% as against conventional garlic planting. Masoumi et al. (2004) have developed an one-row garlic planter comprised of vertical roller-type metering plate and seed hopper driven by electric motor. They investigated the single clove planting rate and miss-planted rate according to roller speed and clove size.

Choi et al. (2008) fabricated an element testing device combining with a metering unit and a planting unit and reported indoor experiment results for the soil punching shape and garlic clove laying status analysis.

In another field test with garlic clove planter attached to the power tiller which enabled hill seeding with an equal distance, Choi et al. (2009) reported to have achieved the one clove planting rate at 88.4% and miss-planted rate at 3.1% in the field condition and one clove planting rate at 90.7% and miss-planted rate at 2.0% in the paddy soil, respectively.

Bakhtiari et al. (2009) developed a tractor-attaching type three-row garlic planter and reported the garlic planting capacity 220,000 cloves/ha, miss-planted rate 12.3%, and damage 1.41%.

As has the garlic planter development history seen above, though many researchers have put efforts on the mechanization of the garlic clove planting, these method are difficult to implement in the garlic cultivation in Korea where garlic cloves are planted on the vinyl mulching over the soil. Also, number of planting row one, six, or tractor-attaching type 12-row etc. are difficult to be adopted since it is hard to obtain sufficient number of plant per unit area as compared with conventional garlic clove planting in Korea. Besides, garlic cultivation area is huge and planting takes a long time, walking-type garlic planter cannot solve the problem of farmers. A riding-type garlic clove planter is evidently demanded at the field.

This study was carried out with the object of developing a self-propelled riding type garlic planter that enables vinyl punching and stable garlic planting for the vinyl mulching practice in Korea.

In this paper, we describe the present study focusing the designing and manufacturing of a prototype garlic planter and the basic testing with the developed prototype.

Materials and Methods

Design target and guidelines

Garlic in Korea is mainly a succeeding crop after paddy cultivation and have to be quickly planted after harvesting rice, then only it will not hamper rice cultivation during the next year. This study was conducted with the objects of developing an excellent garlic clove planter that can minimize garlic cultivation cost by mechanization and has excellent work performance. Garlic has physical properties of various clove size, weight, and shape. Considering the geometric characteristics and cultivation environment of garlic in our land, design guideline has been drawn for the garlic clove planter as follows:

- Engine of the main body and transmission have to be constructed enough to drive the garlic planting device, to have a drive power to move planter as self-propelled type, and drive speed should be appropriately controlled.

- Garlic planter should be manufactured as a riding-type and seed metering and planting devices should be driven by the power transmitted from the main body of the planter.

- Garlic planting width and interval have to be designed enough to secure sufficient numbers of plant per unit area. Also, garlic planter should be equipped a drive part that can work on the ridge width 1,500 mm.

- Garlic planter should be able to plant garlic cloves while punching the vinyl over the vinyl mulching to be adopted in the southern-type garlic cultivation.

- Working performance of the garlic planter with higher than 90% in the single planting rate, miss-planted rate less than 5%, fallen rate less than 5%, and damage rate less than 1% should be achieved.

- Garlic clove planter should be easily transported by the cars, should have good mobility in the farm roads and ridges. Also, it should be structurally safe against over-turn towards front, rear, left, and right side.

Design and manufacturing of a prototype garlic planter

Main body

The main body of garlic clove planter was designed and fabricated as self-propelled riding-type to secure the worker's convenience during garlic planting and mobility of planter. Main body was constructed with an engine, a driving part, a three-point link, and a steering system. Key components of the planter was comprised of gasoline engine (10.3 kW/3,600 rpm, Kukje). The wheel width of drive part was set as 1,632 mm considering width of the ridge in the garlic cultivation field. Four-wheel drive mode was adopted as a driving mode of the drive part so as to be adapted in the slope-area and to secure the drive safety. A small-sized wheels having diameter 650 mm were used to have safe feature during working to avoid over-turn. In addition, rubber-coated steel wheels having width 80 mm was used to enhance the adaptability in the ridge and to secure the number of plant per unit area.

The three-point link controlled by hydraulic power was attached to the garlic clove planter so that attaching/detaching the planting unit can be easily operated and planting depth can be controlled uniformly even if height of the ridge is varied.

Fig. 1 shows the main body of the prototype garlic clove planter. Fig. 2 presents the hydraulic circuit diagram constructed for up and down movement of garlic planting unit. Two- numbers of hydraulic cylinders were installed to control the garlic planter.

Fig. 1.

Prototype of main body.

Fig. 2.

Block diagram of hydraulic circuit for prototype.

Components of Garlic Planter

1. Seed metering unit

In the metering unit of garlic planter, key point for the accurate metering is to retain a contact duration between metering bucket and seeding hopper as long as possible. For the accurate metering, a drum bucket-type metering unit comprised of metering plate, metering cam, metering link, and bucket was designed and fabricated. The principle of metering is that bucket fixed on the metering plate grips one clove taken from the seed hopper and supplies the clove into the planting device while it is repeatedly opened and closed by interacting with metering cam.

The diameter of the base circle of metering cam was set as 50 mm, and stroke was set as 28 mm enough for the bucket to take the garlic clove. Diameter of the nose circle was set as 106 mm. A hexagonal rod cam shaft having diameter 25 mm was used to improve structural safety of the planter.

The seed metering unit was constructed with the three-number steel circular plates and each plate was fastened with bolts not by welding to prevent deformation. Diameter of the circular plate in the seed metering unit was set as 500 mm for exactly supplying the garlic clove to the planting unit considering garlic clove gripping duration and its clove exchange time with the planting unit.

Metering link was divided into no. 1 having and no. 2 having length 90 mm and 108 mm each in order to make bucket movement smooth. The bucket was constructed with three number of rake-shaped plates for stable gripping of garlic clove. Total ten buckets were attached on the seeding metering circular plate with 150 mm interval to obtain sufficient garlic plants in the unit area.

Bucket is operated as shown in Fig. 3. It started opened at point A to supply the garlic clove to the planting unit and then fully opened by rotating 22° more. Bucket is rotated 162° further to grip another garlic clove at point 186°. And then it is rotated 176° more to supply the garlic clove again and repeats this rotational process.

Fig. 3.

Operation principle of metering.

2. Planting unit

Since garlic is planted as hill seeding, seeding unit was designed and fabricated enabling the hill seeding while punching the vinyl after taking one garlic clove at each time from the seeding metering unit. Seeding unit was comprised of circular plate, cam, and hopper.

Planting is executed as the hopper which is fixed on the seeding circular plate safely receives the garlic clove dropped from seed metering unit in a parabolic motion while opening and closing process of hopper is repeated and then plants garlic cloves into the soil. The diameter of the base circle of the seeding cam was set as 184 mm. The stroke of the seeding cam was set as 40 mm considering the average length of the garlic clove was 38 mm so that hopper can be opened wider than this length. Diameter of the nose circle in the cam plate was set as 264 mm. Seeding cam shaft was installed on the same line with the cam shaft of the seed metering unit.

circular plate was constructed with one plate and eight numbers of hoppers. The synchronization ratio between seeding circular plate and seed metering unit was set as 1.25. The diameter of circular plate was set as 400 mm to receive garlic clove stably and to obtain a uniform plant distance 140 mm. As can be seen in Fig. 4, seeding hopper is started opening from point B and plants the garlic clove while punching the vinyl film over the ground. After that, it receives one clove from the seeding metering unit at near 180° and hopper is closed at 210°. Seeding hopper is rotated 80° further while it is closed and repeatedly plants the garlic clove on the ground. The bucket of seeding metering unit and planting hopper of planting unit were rotated towards the same direction to make garlic stably supplied to the planting hopper. Fig. 5 shows the schematic diagram of entire garlic clove planting cycle from gripping garlic clove from the seeding hopper, supplies garlic to the planting unit, and garlic planting by planting unit.

Fig. 4.

Schematic diagram of garlic planting operation principle.

Fig. 5.

The schematic diagram of metering and planting devices.

Accessory devices

A system was built to transfer power from the main body to the seed metering and planting units to drive the seed metering and seeding device effectively as shown in Fig. 6. A seed hopper was installed at front of the seed metering unit to supply garlic clove stably and continuously. In addition, garlic cloves collection bin was installed at the rear side of the seed metering part to recover the missed by the seed metering unit and pushed garlic clove from the seed metering bucket.

Fig. 6.

Power transfer system.

Fig. 7 shows the prototype self-propelled riding type garlic planter with attached 12-row seeding unit comprised of seed metering and planting units one number each. Key specifications of entire prototype garlic planter are tabulated in Table 1.

Fig. 7.

Developed prototype garlic clove planting system.

Basic testing of the prototype

Test for the structural safety

1. Test for the turn-over angle and load sharing on the wheel

Garlic is cultivated mainly on the flat paddy field or on the fields. Yet, garlic field may be located at the slope or steep area. The static turn-over angle towards front, rear, left, and right side were examined for the prototype garlic planter to secure the safety of operation on the uneven fields. Also, the loads on the front and rear wheels were measured to investigate the driving safety and straightness since the seed metering and seeding units are built at the rear part of the prototype garlic clove planter.

2. Analysis of center of gravity

The center of gravity of the prototype garlic planter was measured to examine if the center of gravity is out of the center of the planter and if so how much it is biased. Static turn-over angle, load distribution on each wheel, and center of gravity were measured using turn-over angle test bed and weight measuring instrument available at Division of Agricultural Engineering, the National Academy of Agricultural Science according to the methods recommended by ASABE(American Society of Agricultural and Biological Engineers). Fig. 8 shows the testing arrangement of each testing item. Center of gravity was measured as per OECD Code 2(ISO789-6).

Fig. 8.

Testing arrangement for static falling down angle, load distribution and position of center of gravity.

Seed metering and seeding test

Seed metering test for the garlic clove was performed using the manufactured prototype planter. The garlic clove used in the seed metering test was a southern-type garlic (var. Namdo). The physical properties of garlic used for the seeding metering test are as shown in Table 2.

Seed metering test was conducted after adjusting work speed at three stages of 0.14, 0.22, and 0.24 m/s with garlic clove fed into the seed hopper at specific quantity to investigate characteristics of the seed metering unit. Each of 12-row were simultaneously measured to accurately investigate the characteristics of seed metering. Four measurement items like single clove planting rate, more than two cloves planting rate, miss-planted, and damaged clove rate were chosen to investigate performance of the planter. The performance of the seed metering was examined by rotating the seed metering unit for five times per each speed to obtain a total 60 operation testing data.

Fallen clove rate was simultaneously examined during seed metering test. That means, the cases wherein seeding hopper received the garlic cloves stably and transfers them to the ground were recorded. Also, clove damages by seed metering unit and seeding unit were examined along with the condition of vinyl opening.

The condition of vinyl opening from the first until 12th row as opening length and width were examined for 60 numbers of drilled holes.

Fig. 9.

Planting and film opening status by prototype.

Results and Discussion

Structural safety

Static turn-over angle towards left, right, front, and rear side

The static turn-over angles of the prototype garlic planter towards front and rear side were 35° and 37°, respectively. The static falling down angles of prototype planter towards left and right side were all similar with value 40.1°.

The turn-over angle of the prototype planter is regarded as high since the sideway turn-over angle of a large-sized crawler-type head-feeding combine with six-row is below 36°.

Load distribution on the planter wheels

The load distribution on the planter wheel was analyzed to investigate the drive safety and straightness and the analysis results of load distribution status per wheel are presented in Table 3. The total weight of the planter was 1,174 kg, the load distribution on the front wheel was 438 kg, while the load on the rear wheel was 736 kg. The load distribution on the front wheel was 37.3%. Whereas, the load distribution on the rear wheel was 62.7%. Because the load distribution on the rear wheel was larger, it was judged that the weight can be put on the front part of the planter to secure the drive stability and straightness during planting work.

The load distribution on the left wheel from the front of the planter was 539 kg, and 635 kg on the right wheel. This means that load distribution rate for the left side was 45.9% and the load distribution rate on right side was 54.1% which shows the load at right side was relatively high. It might be because engine is located at right side of the planter and would not affect greatly on the drive stability and straightness of garlic planter.

Center of gravity

The center of the gravity of planter was located at 57.3 cm on the horizontal line from center of the wheel shaft till center of the main body. The height of center of gravity of the prototype garlic planter from ground was 72.7 cm and horizontal distance from the center face towards longitudinal direction to the center of gravity was biased 6.7 cm towards right side.

This location is 46cm back of the driver's seat that would not affect greatly on the safety of driver and garlic planting work.

Seed metering characteristics

Table 4 shows average value of seed metering characteristics according to the working speed of the planter. The seed metering work was executed smoothly from no. 1 seed metering unit until no. 12. Single clove metering rate was 55.2~62.5% and best seed metering was achieved when working speed was 0.22 m/s. While, the two clove metering rate of two cloves was 21.9~25.0%. This value indicates that bucket of the seed metering needs to be improved suiting to the geometric shape of the garlic.

Seed metering rate of single clove and two cloves together showed as high 77.1~87.5%. However, high seed metering of two cloves can lead unbalanced garlic plant growth and abnormal bulb growth, this rate is needed to be reduced. Miss-planted rate was high with value 13.5~19.8% and this rate became reduced when the working speed was 0.22 m/s. High miss-planted rate was attributable by momentarily mixing of cloves inside the seed hopper, thus garlic clove was missed from the space while seed metering bucket passed.

Therefore, it was judged that an accessory device needs to be attached so that garlic can be continuously and uniformly flow to prevent momentarily created gap in the hopper.

The results obtained in the present study showed seed metering rate of two garlic cloves higher by 7% and the miss-planted rate higher more than 10% than those of results by Gard (2003). The comparison result of the present implies that there is need to improve further in the prototype planter in the present study. In particular, unlike previous studies that mostly dealt with planting in bare soil using walk-behind or tractor-attached planters, this study tested the garlic planter under film-mulched condition using a self-propelled riding-type system, which is considered as a distinct feature of this study.

Planting characteristics

Table 4 shows the falling rate of the garlic cloves supplied from the seed metering unit and fallen on the ground not supplied to the planting unit. Falling rate was high with value 24.0~27.1%. While, the garlic falling rate was relatively low with value 24.0% when work speed was 0.22 m/s. High falling rate was due to unstable settling of the garlic inside the hopper when garlic cloves were separated in the bucket of seed metering unit. The reason of unstable settlement of the garlic clove in the planting hopper might be because garlic clove was not correctly separated from the hopper according to the gripping position of the garlic clove by the bucket. Another reason of falling of garlic clove was that when working speed was changed, acceleration speed became faster or slower at the moment of garlic separation from the bucket that caused garlic not supplied into the planting hopper or bounced back even after it was supplied in the seeding hopper. Therefore, it was judged that bucket and planting hopper need to be improved to increase the planting rate. Also, working speed has to be adjusted to maintain the optimum seed metering speed. The damage investigation of the garlic clove by the planter did not produce any damages on the garlic cloves.

The vinyl opening condition using the planting unit was fair from the first till the 12th row. The average vinyl punching length was 6.8 cm and the width was 3.2 cm that indicated there won't be any problem for garlic clove sprout and its coming out from the vinyl mulching.

Although the proposed work performance in the design target and guideline could not be fully achieved in the basic test, the prototype showed stable mechanical operation under field conditions. Considering that the planter was tested under film-mulched conditions and incorporated a riding-type self-propelled system, the observed performance metrics represent a promising step toward reducing labor intensity in southern-type garlic cultivation. Compared to previous garlic planters that were either manually operated or tractor-attached and tested without vinyl mulching, this study provides a distinct contribution through its integration of film punching, multi-row planting, and mobility suited for narrow ridges. This system-level design, tailored to local field conditions, offers a promising approach for enhancing practicality and fostering innovation in garlic planter development.

Summary and Conclusion

A self-propelled garlic planter for the vinyl mulching facilities for the garlic cultivation was developed and its basic test was performed for the southern-type garlic cultivation which is practicing manually. The obtained results with the developed prototype garlic clove planter are as below.

(1)The static falling down angle of the prototype planter towards front and rear side was wider than 35° which showed almost similar stability with track-link mode head-feeding type combines. The load distribution on each wheel of the planter was 37.3% for the front wheel and 62.7% for the rear wheel showing higher load imposed on the rear wheel. The load distribution rate on the right side was found as 54.1% higher than that of left side wheel.

(2)The center of gravity was at 46cm of the rear part of the driver’s seat, thus it did not significantly affect on the safety of driver and garlic planting operation.

(3)The performance of seed metering and planting unit of the prototype planter showed the best when work speed was 0.22 m/s. Other performances like seed metering rate of single clove at 62.5%, seed metering rate of two cloves at 24.0%, miss-planted rate at 13.5%, and falling rate at 24% were obtained.

(4)The vinyl punching length 6.8cm and width 3.2% were judged as optimum for the garlic sprouting and its growth out of the vinyl mulching.

(5)It was also judged that the seed metering and planting units need to be improved so as to increase the single clove metering rate and to reduce the miss-planted rate and falling rate.