Korea produces approximately 270,000–330,000 tonnes of garlic annually — the third most cultivated vegetable crop after radish and cabbage — making it one of the most commercially significant highland crops that stone clearing directly affects. Unlike potato, where Grade 1 is defined primarily by tuber size and skin condition, garlic Grade 1 is defined by a single non-negotiable criterion: the bulb must be whole, symmetrical, and undivided at the base. A garlic bulb that has been split — even partially — by lateral stone resistance during its underground development is permanently disqualified from the Grade 1 premium market regardless of its size, skin quality, or flavour.
Korean garlic farming stone clearing is not simply about improving yield. It is about protecting an investment that runs for five to six months in the ground before any result is visible — and ensuring that the biology of bulb development is allowed to complete correctly. This guide covers the specific stone clearing requirements for Korean highland and lowland garlic production, the biology behind the Grade 1 standard, the Euiseong premium certification system that stone clearing enables, and the complete field preparation protocol from autumn THOR 2.4 pass through to PSW-3200 raised-bed formation.
The Garlic Grade 1 Standard — Why Stones Create the Damage No Other Factor Does
Korean garlic bulb development occurs underground from March through May on a standard winter garlic production cycle. The bulb initiates at the base of the stem where the clove wrappers form — at a depth of 8–15 cm below the ridge surface. As the bulb expands horizontally from this initiation point, it encounters whatever solid material is in the surrounding soil. The physical mechanism of stone damage in garlic is fundamentally different from the damage mechanism in potato:
Potato damage mechanism
A stone redirects the potato’s developing taproot — the root grows around the stone, producing a forked tuber. The potato continues to grow around the obstruction, producing a misshapen but often full-sized result. Damage is expressed in the elongated or forked tuber shape.
Garlic damage mechanism
A stone applies lateral compressive resistance against the expanding garlic bulb. The bulb’s outer wrapper, expanding outward under its growth pressure, meets the stone and is redirected — the bulb splits its clove arrangement along one or more cleavage planes, producing a “split” or “double-round” bulb that cannot be sold as Grade 1 whole garlic. Unlike potato, the damage is to the internal architecture — the bulb can be near full size but completely Grade 2.
Garlic Bulb Development — How Stone Contact Creates a Grade 2 Outcome
Stone-Free Field → Grade 1
Whole, symmetric, unbroken wrapper
→ 8,000–20,000 KRW/Kg
Stone at
development depth
Stone-Present Field → Grade 2
Split wrapper, displaced cloves
→ 500–1,500 KRW/Kg
Diagram schematic only — illustrates how lateral stone resistance displaces garlic clove arrangement during underground development.
| Grade | Definition | Un-cleared field proportion | Cleared field proportion | Price range KRW/Kg |
|---|---|---|---|---|
| Grade 1 (sang-pum (Grade 1)) | Whole, unbroken wrapper. 6–8 even cloves. No splits, cracks, or deformation. | 55–68% | 87–94% | 4,000–20,000 |
| Grade 2 (jung-pum (Grade 2)) | Minor wrapper split, slight asymmetry, small cloves missing. Suitable for food service and processing. | 20–28% | 5–10% | 1,500–4,000 |
| Grade 3 / Processing | Significant splitting, double-round, severely misshapen. Minced garlic and extract processing only. | 12–17% | 1–3% | 500–1,500 |
The grade shift from 65% Grade 1 (un-cleared) to 91% Grade 1 (stone-cleared) on a Korean garlic farm represents a 40% improvement in the proportion of produce receiving the premium price — a revenue multiplier that operates on every kilogram produced for as long as the field remains cleared. At Euiseong premium market Grade 1 pricing (8,000–20,000 KRW/Kg for certified whole dried garlic), this grade shift is among the highest-value revenue improvements that stone clearing produces across all Korean highland crops.
The Euiseong Premium — How Korea’s Most Valuable Garlic Origin Depends on Stone-Free Production
Euiseong County (North Gyeongsang Province) is the most recognised garlic origin in Korea — the registered geographic indication for Euiseong garlic carries a price premium of 2–5× over equivalent-quality garlic from non-certified origins. Understanding what the Euiseong certification requires — and how stone clearing interacts with those requirements — reveals why the clearing investment is a prerequisite for the certification, not an add-on to it.
Euiseong Garlic Certified Origin — Key Production Requirements
Registered agricultural field within Euiseong County, North Gyeongsang Province. Field must be listed on the county’s certified origin field registry. Stone-cleared fields receive preferential registry listing status — un-cleared fields with documented production quality below Grade 1 threshold may be de-listed on quality review.
Minimum 85% Grade 1 whole bulb in any lot submitted for certified origin labelling. This threshold is routinely achieved only on stone-cleared fields — the 55–68% Grade 1 range on un-cleared fields falls below the certification floor, making un-cleared field production structurally ineligible for certified origin status regardless of other factors.
Euiseong certified origin requires production using the registered Euiseong garlic ecotype (smaller clove, more pungent, higher allicin content than standard Korean garlic varieties). The ecotype’s smaller bulb size makes it more vulnerable to stone-related deformation than standard commercial varieties — stone clearance is even more important for the Euiseong ecotype than for standard Korean garlic.
pH 6.0–6.5 for the Euiseong ecotype — tighter than standard Korean garlic’s acceptable range of 5.8–7.0. On granite-parent Euiseong soils (naturally pH 4.5–5.5), annual lime application through the DCW 2.2 spreader is a certification maintenance requirement, not optional soil improvement.
Euiseong certified origin sales to major Korean retailers (E-Mart, Homeplus, Costco Korea) increasingly require GAP certification alongside the origin certificate. GAP field registration requires the stone-cleared, documented field record that the THOR 2.4 + CT-2100 system’s probe verification procedure produces. The two certifications are operationally linked through the field preparation record.
For Euiseong garlic farmers, the stone clearing investment is not evaluated against a generic Korean highland ROI framework — it is evaluated against the specific price ceiling of Euiseong certified whole dried garlic at the premium market. The ceiling is substantially higher than for any other Korean highland crop covered in this guide series, which is why the clearing investment’s payback period on Euiseong garlic production is the shortest per-hectare of any Korean highland crop once the certification is established.
Stone Clearing Depth and Timing — Why Garlic Requires the October Window
alt=”CT-2100 rock picker completing stone collection after THOR 2.4 pass — for Korean garlic production, the CT-2100 collection must be completed before late October to allow the PSW-3200 raised-bed preparation and November winter garlic planting on schedule”
title=”CT-2100 Collection Timing for Garlic — October Window is Mandatory”
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The Korean Garlic Production Cycle — Understanding the Timing Constraint
Korean winter garlic (the dominant production type in Euiseong and Gyeongnam regions) is planted in October–November and harvested in May–June the following year. This planting timing creates a non-negotiable constraint for stone clearing: the THOR 2.4 clearing pass, the CT-2100 collection, and the PSW-3200 raised-bed preparation must all be completed before the November planting window. This gives a maximum of 4–6 weeks from the preceding crop’s harvest (typically late September for summer vegetables or early autumn potato) to complete the full stone management and bed preparation sequence.
Stone Clearing Depth for Garlic — 25-28cm vs Potato’s 30cm
Korean garlic bulbs develop at 8–15 cm depth and their root systems extend to 20–25 cm. The stone clearing depth requirement for garlic is therefore 25–28 cm — shallower than potato (30 cm) and substantially shallower than ginseng (40 cm). The THOR 2.4 operating at 25–28 cm depth on a garlic preparation pass can typically move at a slightly higher forward speed than on a potato or ginseng pass, because the clearing depth is within the machine’s most efficient operating zone for Korean highland granite at the standard stone density.
One important nuance: garlic’s root zone is shallower than potato’s, but the stones that cause the most damage to garlic bulbs are not primarily the deep-embedded stones at 25–30 cm depth — they are the 10–20 cm stones that sit directly at bulb development height. A THOR 2.4 pass that targets 25–28 cm depth fragments both the surface stone layer and the 10–20 cm zone in a single pass on a previously un-cleared field. On a field that has been cleared in prior years to 30 cm, the garlic annual maintenance pass at 20–22 cm is sufficient — the stones that remained at 20–25 cm depth after the initial clearing are smaller and fewer after several frost-heave cycles have progressively moved sub-surface material toward the surface where the CT-2100 can collect it.
PSW-3200 Garlic Raised-Bed Specification — Different From Potato Ridge Formation
Garlic production in Korea uses raised beds rather than the narrower ridges used for potato. The raised-bed geometry for garlic is specific to its row spacing requirements (Korean garlic is typically planted at 15–18 cm between-plant spacing in multiple rows per bed) and its drainage requirement (raised beds ensure that the bulb development zone remains aerated through the spring monsoon period).
PSW-3200 Garlic Raised-Bed Specification vs Potato Ridge
El PSW-3200 rock crusher at 1000 RPM, 3.0 m width (set for typical garlic bed spacing), operated at 2.0 km/h creates the 5–8 mm fine-tilth bed top that manual garlic clove planting or mechanical transplanting requires. The wider garlic bed allows 4–6 rows of planting per bed pass — covering the same ground area as potato production with fewer PSW-3200 passes because the bed does not require the precise ridge peak geometry that potato planting machines demand.
pH Management for Garlic — Why the DCW 2.2 Lime Pass Is Non-Negotiable
Garlic is one of the most pH-sensitive Korean highland crops. The optimal range of pH 6.0–6.5 is narrow — below pH 5.8, manganese toxicity and calcium deficiency suppress bulb development; above pH 7.0, iron chlorosis appears and allicin synthesis is reduced, lowering the flavour intensity that the Euiseong premium commands. Korean granite parent soils start at pH 4.5–5.5 and acidify over time under cropping.
Korean garlic fields typically require 2.5–3.5 t/ha of agricultural lime per application cycle (every 1–2 years) to maintain pH in the 6.0–6.5 range on granite soils under cropping. The DCW 2.2’s 2,140 mm spreading width and adjustable application rate allows precise coverage at these rates on highland terrace dimensions.
Apply lime after CT-2100 stone collection is complete but before the PSW-3200 incorporation pass — the sequence is THOR 2.4 fragmentation → CT-2100 collection → DCW 2.2 lime spread → PSW-3200 incorporation pass. This sequence ensures the lime is distributed through the full 22–25 cm profile in a single PSW-3200 pass, not left on the surface.
Do not apply lime and nitrogen fertiliser simultaneously or within 7 days of each other. Lime raises soil pH immediately around the granule — if nitrogen (ammonium-based fertiliser) is applied simultaneously, the elevated pH around the lime granule converts ammonium-N to ammonia gas, causing significant nitrogen volatilisation loss. Apply lime at least 1 week before or after any nitrogen fertiliser application.
5-Year ROI — Korean Garlic Stone Clearing Investment vs Protected Revenue
Garlic is an annual crop with a 6–8 month production cycle — shorter than ginseng (4–6 years) and producing annual revenue rather than the multi-year compounding risk structure of ginseng. However, garlic’s annual revenue per hectare is substantially higher than potato’s, making the 5-year ROI calculation for garlic stone clearing significantly more favourable than for potato at equivalent clearing cost:
5-Year Garlic Stone Clearing ROI — 1 ha Reference Field (Euiseong type, standard highland rotation)
Yield ~8–10 t/ha. Grade 1: 65%. Price: 2,500 KRW/Kg (non-certified, standard market). Annual gross: ~16M–20M KRW.
Yield ~9–11 t/ha. Grade 1: 91%. Price: 6,000–12,000 KRW/Kg (Euiseong certified origin, direct market). Annual gross: ~49M–110M KRW. Using conservative 7,000 KRW/Kg: ~57M KRW/year.
57M – 18M = ~39M KRW/year net revenue improvement per hectare.
THOR 2.4 + CT-2100 after 40% subsidy: ~24M KRW. Shared with potato and other crops — garlic’s share of the clearing investment: ~8M–12M KRW (proportional to the garlic area’s share of total annual cleared field use).
~10–14 weeks after first Euiseong-certified harvest. The garlic area’s share of the clearing cost is recovered in the first quarter of the first post-clearing production season.
~39M KRW/year × 5 years = ~195M KRW additional revenue from garlic alone, against a garlic-share clearing cost of 8M–12M KRW. Return on garlic clearing investment: 16–24× over 5 years.
All figures are representative estimates using conservative pricing. Euiseong premium prices vary with annual supply and market conditions. Certification must be established before the Euiseong price applies — expect 1 full season at standard non-certified pricing while the certification process completes.
Preguntas frecuentes
Korean garlic farming stone clearing guide — what is the correct THOR 2.4 depth for garlic fields?
The recommended THOR 2.4 clearing depth for Korean garlic field preparation is 25–28 cm on a first-season clearance of un-cleared ground, and 20–22 cm for annual maintenance passes on previously cleared fields. The 25–28 cm initial clearing depth targets the 10–25 cm stone zone that directly affects garlic bulb development — stones at this depth are the primary cause of Grade 2 bulb splitting. Stones below 25–28 cm are generally below the garlic bulb’s development and root zone and do not need to be targeted in the garlic-specific clearing pass (unlike ginseng, which requires clearing to 40 cm for the taproot development zone). The THOR 2.4 at 25–28 cm operating depth on Korean highland granite at garlic-season soil moisture conditions (typically post-October harvest, moderately dry) can operate at 1.5–2.0 km/h forward speed — slightly faster than the potato or ginseng preparation depth settings.
What is the Euiseong garlic stone-free production standard and can other Korean counties achieve the same price premium?
Euiseong garlic’s certified geographic indication (GI) is specific to Euiseong County, North Gyeongsang Province — it cannot be claimed by garlic from other counties regardless of production method or quality level. However, other Korean garlic production regions have developed their own premium origin identities that command above-standard pricing for Grade 1 whole dried garlic from verified origins: Namhae garlic (South Gyeongsang), Taean garlic (South Chungcheong), and Uiseong garlic all command premiums above the standard cooperative market price for whole Grade 1 garlic from certified origin producers. The stone-free Grade 1 production threshold that enables premium market access applies across all these regional designations — the exact price premium varies by region and market year but the underlying production requirement (85%+ Grade 1 whole bulb) is consistent. Korea Watanabe provides guidance on the premium destination applicable to the specific garlic production county for any customer consultation.
Can garlic and potato be grown in rotation on the same stone-cleared field?
Yes — garlic and potato rotation on the same stone-cleared Korean highland field is agronomically compatible and economically advantageous. Both crops benefit from the same stone-clearing standard (though garlic at 25 cm vs potato at 30 cm means the garlic field’s clearing is effectively a subset of the potato field’s clearing requirement). The rotation breaks the monoculture disease build-up that both crops are prone to: potato follows garlic without the solanaceous pathogen accumulation that occurs under continuous potato production, and garlic follows potato with the benefit of the soil structural improvement from the potato’s deeper root system. One important constraint: do not plant garlic in soil where alliums (garlic, onion, leek) have grown within the previous 3 years — the soil-borne pathogen Fusarium culmorum accumulates under continuous allium cropping and directly attacks garlic roots. A cereal or brassica break crop is recommended between garlic rotations on the same field. Korea Watanabe’s rotation planning consultation covers the optimal crop sequence for the specific cleared field.
Is there a specific garlic variety that responds better to stone clearing than others in Korean highland conditions?
The Euiseong ecotype (small-clove, high-pungency winter variety) responds most dramatically to stone clearing because its smaller bulb diameter makes it more sensitive to lateral stone resistance than large-bulb commercial varieties. Standard Korean commercial winter garlic (Namdo, Daesan types) also benefits significantly from stone clearing but at slightly lower Grade 1 uplift percentage than the Euiseong ecotype. For stone-cleared fields being developed for premium garlic production, Korea Watanabe recommends starting with the Euiseong ecotype if the field is in the Euiseong County zone, or the regionally appropriate ecotype for other certified origin zones. For non-premium market production, commercial winter varieties (Namdo-type) are more tolerant of residual stone populations than the Euiseong ecotype and produce reliable Grade 1 proportions on fields that have received partial rather than complete stone clearing treatment.
Does the Korean agricultural machinery subsidy apply to THOR 2.4 purchases for garlic field preparation specifically?
Yes — the Korean agricultural machinery subsidy applies to the THOR 2.4 rock crusher regardless of which crop the cleared field will be used for. The subsidy is applied to the machine purchase, not to the crop — a garlic farmer purchasing a THOR 2.4 for garlic field preparation receives the same 40–50% subsidy rate as a potato farmer purchasing for potato field preparation. The subsidy application requires a registered agricultural field and a farm household registration, both of which a garlic farmer in a certified origin zone would typically already hold. Korea Watanabe prepares the subsidy documentation for garlic farmers in the same way as for potato farmers — the January application window, county quota system, and 5-year compliance period all apply equally. Contact Korea Watanabe in October–November to begin the combined subsidy and field preparation planning process for the following January application window.
Garlic Field Preparation — October is the Critical Window
Field area + current stone density + target garlic variety (Euiseong ecotype or commercial) + existing tractor HP → Korea Watanabe provides the October clearing schedule, THOR 2.4 depth protocol, PSW-3200 raised-bed specification, DCW 2.2 lime rate and 2026 subsidy calculation.
Editor: Cxm
