Horticultural Science and Technology ISSN:1226-8763(Print) 2465-8588(Online) 원예과학기술지

Though the mechanisms are not yet fully understood, the macro- and micro-nutrients, amino acids, and hormone-like growth substances present in plants (whole plants and their extracts) may lead to biostimulatory activities when applied to crops. This study was conducted to determine the growth promotion effects on lettuce (Lactuca sativa L.) of plant extracts obtained by different extraction methods (water, boiling water, fermentation, and ethanol) from 31 agricultural materials. We also determined the growth promotion effects of three other leguminous crop extracts on lettuce. In total, these 31 different agricultural materials produced 82 different extracts. The most effective extracts were water and boiled water extracts of Chinese chive (Allium tuberosum), water extracts of soybean leaves (cvs. Daewon and Haepum), and water, fermentation, and ethanol extracts of soybean stems (cv. Daewon). These induced a 31 - 45% increase in shoot fresh weight of lettuce compared with control plants. Chinese chive, soybean leaf, and soybean stem extracts had a greater impact on shoot fresh weight of lettuce when applied at 20 days after seeding (DAS) than when applied at 30 and 40 DAS. In addition, when extracts from Chinese chive and soybean leaf and stem were used, the shoot fresh weight of lettuce was higher at 7 days after treatment (DAT) than at 14 and 21 DAT. The shoot fresh weight of lettuce was 13 - 15% higher when the selected extracts were applied twice instead of once. Moreover, the growth promotion effects of the selected plant extracts were also observed in endive and broccoli, but not in pak choi and kale. Additionally, the growth promotion of lettuce was higher in response to soybean leaf and stem extracts than extracts of other leguminous crops (cowpea, mung bean, and red bean). The selected extracts showed higher growth promotion effects on lettuce than those of urea and a commercial extract. Overall, the results indicate that the selected plant extracts can be used for growth promotion in organic cultivation of various crops.