Competitive ability of different upland rice cultivars against weeds [Philippines]
1986
Seoane, H.Q.
Rottboellia cochinchinensis, (Lour.) Clayton., Digitaria ciliaris (Retz) Koel., Eleusine indica (L.) Gaertn., Murdannia nudiflora (L.) Brenan, Mimosa pudica L., Amaranthus spinosus L. and Cyperus rotundus L. were the predominant weed species. It was observed that leaf water potential during the drought and nutrient content was superior in the weed species than in the rice cultivars. Weed weights per ha were highly significantly different among cultivars varying from 3.1 to 5.9 t/ha. The tall cultivar group was the most competitive against weeds showing the lowest weed weight in both weeding levels. The superiority of the tall cultivars in weed suppression was not evident at the early sampling time. It was expressed during the period between 70 DAE and harvest, where weed weight accumulation between cultivar groups diverged substantially. Among the plant characters observed, plant height was most strongly related to low weed weight. Weed weights were also negatively correlated with plant canopy height, rice dry weight, tiller number, leaf angle and leaf number. Grain yields were negatively correlated with weed weights under the low weeding level. Grain yield was positively correlated with plant height, rice dry weight, and leaf angle at harvest. Leaf area index and tiller number were not significantly correlated with grain yield. The short cultivars at the Batangas site obtained the highest yields. This was attributed to the lower density of weeds and better distribution of rainfall during the reproductive stage. Entries which had the highest weed suppression ability were the tall cultivars. The best intermediate cultivars demonstrated weed supression ability similar to the tall cultivars. The short cultivars as a group had the lowest weed suppression ability
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