Effect of Burial Depth on Seedling Emergence of Mimosa pigra L. Invaded Areas in Southern Province, Sri Lanka.

Abstract

Mimosa pigra L., belongs to the family Fabaceae, commonly known as the giant sensitive plant or giant mimosa, and is recognized as a significant invasive weed, that originated in the tropical American region, from Mexico to Argentina. M. pigra was first reported in Sri Lanka in 1997 and subsequently colonized the Central and North-western provinces, spreading into other regions, including the Southern province. M. pigra has invaded cultivable lands, including fallow paddy fields, and according to previous research, nearly 27 ha of land were invaded by M. pigra within the study area. This study aimed to evaluate the germination of M. pigra seedlings in different soil depths of the seed bank. Seed bank samples were collected from Akuressa divisional secretariat divisions and Paraduwa GN divisions in the Southern province of Sri Lanka, where the M. pigra invasion is significant. The experiment followed the randomized complete block design. Samples were collected from each quadrat using a 20 × 20 cm surface area frame to a depth of 30 cm, segmented into a 5 cm depth series. A total of 120 samples were obtained from 20 sampling points, including four control points. The depth intervals were designated as follows: A (0–5 cm), B (5–10 cm), C (10–15 cm), D (15–20 cm), E (20–25 cm), and F (25–30 cm). Seed bank samples were allowed to germinate, and the emergence of M. pigra and other vegetation types in different soil depths were counted by visual observation and recorded weekly up to eight weeks. The emergence of M. pigra declines with the soil depth and is abundant in shallower depths (0-5 and 5-10 cm). The Average emergence per 1 × 10-3 m3 of M. pigra is as follows: A (1.55), B (0.8), C (0.15), D (0.2), E (0.33), and F (0.05). According to these results, the emergence declines with increasing depth. Therefore, it is recommended that land preparation in M. pigra invaded fields be conducted at a ploughing depth below 10 cm to reduce seed exposure and minimize subsequent seedling emergence.