Weed Flora Composition in Upland Direct Seeded Rice in Brahmaputra River Ecotones and Edges in Majuli District, Assam

Abstract

Background: The River Brahmaputra is one of the largest braided rivers in the world, where the island and bars (“Chapories”) are formed almost annually by erosion and deposition, which are good agricultural lands, as most of the depositions are extremely fertile and possess ready water source in close proximity. With an aim to depict the weed vegetation pattern in upland direct seeded rice ecosystem in such an ecotone zone, Chapories of Majuli district were surveyed during 2021 and 2022. Methods: One square meter quadrates were plotted in between 20 to 65 days after sowing (before flowering) of rice to study the weed status in the critical period of crop weed competition in four locations. Result: Study recorded altogether 55 species of weedy nature in four locations with as many as 39 broadleaved species belonging to 25 families, 3 sedges and 13 grasses, which represented a great diversity with several unusual species unique to chapori areas. Isolation of location - 4 by water channel has contributed in increasing dissimilarity with respect to weed flora, though river water might have had great role in distribution of weeds especially the stubble borne perennial species. The cumulative IVI of grass species was also 30.4 per cent higher in this isolated location than the non-grass species, unlike the locations that had land connectivity with shore areas.