Weeds of Paddy Field at Kirtipur, Kathmandu

Abstract

Paddy (Oryza sativa L. var. Taiching-127) fields of Kirtipur, central Nepal, were studied to evaluate the effects of weeds on crop yield during June to October 2003. Weed community was recorded in permanently marked plots (2 x 2 m 2 each), and grain and straw yields were measured. The effect of aqueous extracts (2 to 10%) of leaf, stem and root of dominant weeds (Echinochloa colona, E. crusgalli, Cyperus iria and Ageratum conyzoides) on germination and seedling growth of the paddy (Taiching-127) was examined in the laboratory. Altogether 52 weed species (27 dicot and 25 monocot) belonging to 32 genera and 15 families infested the paddy. The maximum weed density was observed in September (105 pl/m 2 ). There was significant reduction in straw and grain yield of paddy in weedy plots and negative correlation between weed species richness and straw yield. Crop weed competition reduced straw yield by 13% to 38% and grain yield by 25% to 47%. Weed growth changed pH and reduced soil nitrogen and phosphorus content. Aqueous extracts of root, stem and leaf of dominant weeds (Echinochloa colona, E. crus-galli, Cyperus iria and Ageratum conyzoides) showed a weak effect on seeds germination however most of them had inhibitory effect on root and shoot elongation of paddy seedlings. Root elongation was more sensitive to allelopathic inhibition than shoot elongation. Stem extract of these weeds showed higher inhibition on seedling growth of paddy than leaf and root extract except in Ageratum conyzoides in which root extract showed highest inhibition.

Wetland Plants and their Local Uses: Observations from Rampur Ghol, Chitwan, Nepal

“…(fi g. 1). The number of species recorded in this study is higher than that of the total number of species reported in previous studies in Koshi Tappu (Shrestha, 1996), Biratnagar (Niroula & Singh, 2010, 2011, Kirtipur (Manandhar, 2004), Beeshazar (Dangol, 2000-2001, Jha, 2007 and Rampur Ghol (Dangol, 1998(Dangol, -1999. The highest generic diversity was contributed by the Poaceae (17 genera) followed by Asteraceae (10 genera), Cyperaceae (6 genera), Scrophulariaceae (5 genera), Commelinaceae and Hydrocharitaceae (4 genera each), Acanthaceae, Apiaceae and Verbenaceae (3 genera each), and Polygonaceae, Urticaceae, Alismataceae, Araceae, Fabaceae, Lamiaceae and Lemnaceae (2 genera each).…”

Spring weed communities of rice agrocoenoses in central Nepal

“…40-60 species (e.g. Manandhar et al 2007, Bhatt et al 2009, Sapkota et al 2010. The richness of rice agrocoenoses is surely related to the extremely rich species pool in the whole country.…”

“…Losses due to weeds have been estimated at 12% of the crop yields (Manandhar et al 2007). Considerable progress in weed control has been achieved with various measures such as ensuring the purity of rice seed, the proper selection of cultivar and seeding rate, the proper planting method, good land preparation and water management, hand weeding and chemical weed control, as well as crop rotation (De Datta 1981), used together in a system of integrated weed management.…”

“…In transplanted or deepwater plantings the weeds are limited by unsuitable conditions for establishment of plants. Direct seeded rice crops are the most weed-infested with yearly yield losses of up to 75% (Manandhar et al 2007).…”

Study of Management Practices for Lowland Rice in Nepalese Context

“…The major weed species recorded in the paddy fields of Kirtipur were Cyperus difformis, Echinochloa colona, Cyperus iria, Ageratum conyzoides, Spilanthes iabadicensis, Drymaria diandra, Galinsoga parviflora Cab etc [11,12].…”