Abundance and mortality of weed species en upland and lowland soil seed bank

Abstract

Abundance and mortality of weeds of upland (Joydebpur) and lowland (Manikganj) soil seed bank at three soil depths (0-5 cm, 5-10 cm and 10-15 cm) were determined under three temperature regimes (30/29°C, 32/23°C, and 23/12°C), during March, 1992 to December, 1992 at the Institute of Postgraduate Studies in Agriculture. In upland, 14 weed species were identified and the predominant species were Echittochloa colonum (19.76%), Cyperus iria (17.81%), and Fimbristylis miliacea (12.46%). In lowland, 13 weed species were identified and the most predominant species were Enhydra fluctnans (23.40%) and Cyperus iria (19.30%). The abundance of weed species decreased with increases in the depth of the soil. Mortality of weed seedlings was higher in upland soil than lowland. The mortality rate was the highest at vegetative stage and the lowest at maturity stage, regardless of depth or temperature. The mortality rate of weed seedlings were greater in upland soil than lowland soil. At 32/23°C and 23/12°C, the mortality rate of weed seedlings decreased gradually with increases in depths.