Major weeds and dominance patterns in rainfed rice-onion cropping system
1999
Baltazar, A.M. | Martin, E.C. | Casimero, M.C. | Bariuan, F.V. | Obien, S.R. | De Datta, S.K.
The major weeds infesting rainfed rice-onion systems were identified in 13 farms in three villages in San Jose, Nueva Ecija, Philippines, the Asian site of the Integrated Pest Management Collaborative Research Support Program (IPM CRSP). The kind and density of weed species were determined using the quadrat sampling method from 1994 to 1997 wet and dry seasons. About 20 weed species each were observed in the rice and onion crops. However, three species in each crop emerged as most dominant: Ludwigia spp, Cyperus rotundus, and Echinochloa spp. in rice and Cyperus rotundus, Cleome viscosa and Trianthema portulacastrum in onion. One village had less species and kinds of weeds than the other two villages. A carry-over of dominant weeds across crops occurred distinctly in all the three villages. Certain upland species normally occurring only during the onion crop are increasing in populations in lowland rice, apparently caused by insufficient flooding during the rice rotation and enhanced by the alternate wet-dry annual rotation pattern. Over time, this could result in dominant species shifts in rainfed rice-vegetable cropping system, not only in the Asian site but also in other rainfed areas in the country with similar cropping patterns and weed populations
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