Rain-shelter soil cultivation as a rainfall risk adaptation option for sustainable lemon balm production in a Korean highland field assessment

Abstract

Sustainable crop production requires strategies that stabilize the supply of high-value herb raw materials under rainfall and climate variability. Lemon balm ( Melissa officinalis L.) is a medicinal, culinary, and aromatic herb whose commercial value depends largely on stable leaf biomass. This exploratory, single-season, fixed-site field assessment compared adjacent plastic-house rain-shelter (PH) and open-field (PN) soil cultivation in the Pyeongchang highland area, Republic of Korea, during 0–62 days after transplanting (DAT). PH excluded direct rainfall and received 44.0 mm of controlled irrigation, whereas PN received 527.2 mm of gross water input, including 385.5 mm of July rainfall. PH had lower cumulative total shortwave radiation, slightly higher mean temperature, lower period-level relative humidity, and a higher calculated mean vapor pressure deficit than PN. At 62 DAT, PH showed greater shoot fresh weight and shoot, leaf, and root dry matter, while leaf fraction remained similar between systems. Area-based leaf dry matter, root-to-shoot ratio, and shoot dry-matter percentage also supported greater whole-plant vigor in PH. However, the cultivation systems were not independently replicated, baseline soil properties were unavailable, and soil-water status, leaf wetness, disease incidence, gas exchange, leaf area, and phytochemical quality were not measured. The observed contrast is therefore interpreted as an integrated system-level association rather than a causal effect of rainfall exclusion or any single microclimatic factor. Rain-shelter soil cultivation warrants independently replicated, soil-characterized, multi-year evaluation as a rainfall-risk adaptation option for monsoon-exposed highland herb production.