Weed flora landscapes of the Muda rice granary in the new millennium: A descriptive an

M. Azmi and B.B. Baki

Abstract

Weed surveys were conducted from 2001–2005 to ascertain the dominant weed species in the Muda area. A total of 58 weed species belonging to 26 families, comprising 27 broad-leaved weeds, 14 grasses, 12 sedges and 5 aquatic plants, were recorded. The Sorenson’s Index of Similarity indicated that at least 74.4% of the listed species prevailed in all five seasons. An almost similar trend in weed species abundance and dominance in each season was also observed. Quantitative estimates based on percentage of area infested showed the dominance and almost ubiquitous status of the Oryza sativa complex (weedy rice), Echinochloa crus-galli complex, Leptochloa chinensis and Ludwigia hyssopifolia in the Muda rice area. The hierarchical dominance of weed type according to percentage of field infested ratio in the Muda area was in the order of grasses > broadleaved weeds > sedges > aquatics. Canonical correspondence analysis (CCA) showed commonality in dominant species occurrence in four out of five seasons. Fimbristylis acuminata, Cyperus polystachyos, and Echinochloa stagnina were highly prevalent in the off-season of 2001, while Oryza rufipogon was highly associated in the off-season of 2002. There was no indication of preferential season prevalence among the weed species in the off-season of 2003, despite a relatively higher rainfall vis-à-vis the off-seasons of 2001 and 2002. The offseason of 2004 registered measurable association between species dominance in Azolla pinnata and Salvinia molesta and total average annual rainfall. The relatively low total average annual rainfall in the off-season 2005 registered higher species diversity as indicated by the vector lengths in the CCA, with particular dominance of Hydrilla verticillata, Paspalum longifolium, Ipomoea aquatica and Commelina nudiflora.

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