Allelopathic effect of hemp leaf on germination and growth of some crop and weed species

Abstract

At present, farmers are increasingly on hemp (Cannabis sativa L.) cultivation due to its wide range of applications, resulting in a significant increase in agricultural waste materials. It has been reported that hemp produces allelochemicals, which can inhibit the growth of neighboring plants. The objective of this experiment is to study the allelopathic effects of hemp leaves on the germination and growth of 10 different species (rice, corn, wheat, itchgrass, feather pennisetum, chinese kale, lettuce, pea bean, waterkanon, and siam weed), and to investigate its autotoxicity, using the sandwich method. The result showed that hemp dry leaves release allelochemicals that significantly inhibit the germination, shoot length, root length, fresh weight, and dry weight of all 10 tested plant species. Increasing the concentration of the dry leaf further enhanced the inhibitory effects, with a stronger tendency to inhibit dicotyledonous plants compared to monocotyledonous plants. The dry leaf had the most significant inhibitory effect on the germination and growth of waterkanon. After exposure to a concentration of 1.43 mg DW/mL agar, it resulted in inhibition levels exceeding 80% for germination, shoot length, and root length. Moreover, when subjected to a concentration exceeding 7.14 mg DW/mL agar, it led to complete inhibition, reaching 100%. Regarding autotoxicity, hemp dry leaf with low concentrations did not affect the germination and promoted the growth of hemp seedlings. However, hemp dry leaf with a concentration of 7.14 mg DW/mL agar or higher significantly inhibited the germination and seedling growth of hemp. These results revealed that hemp dry leaf had the allelopathic potential to control germination and growth of other plant species.