Rice is the staple food for many urban populations in Niger. However, its production is characterized by low yields due to several constraints, including high weed pressure. This study, carried out on three rice-growing sites in Tillabéri, aimed to: (i) identify the most harmful rice weeds, and (ii) determine their effects on growth parameters and grain yield. It used weed identification tools and an experimental design in complete blocks with four (4) repetitions corresponding to four farmers' plots, including two controls (weeded) and two experimental (unweeded). Two rice growth parameters (number of tillers per hill and plant height) and four yield characteristics (number of panicles per hill, number of infertile grains, number of fertile grains, and grain yield) were evaluated. Thirty (30) weed species, belonging to Poaceae (45.12%), Cyperaceae (18.29%), and broadleaf weeds families (36.59%), were recorded. The most harmful weed species are Marsilea quadrifolia, Juncus bufonius, Rotala indica, Ludwigia peploides, Cyperus difformis, Sphenoclea zeylanica, and Echinochloa crus-galli. The effect of weeds is significant (Fisher's test at the 5% significance level) on growth parameters and most yield characteristics. Thus, the effect of weeds on rice is characterized by a significant reduction in plant height (47.64%), the number of tillers per clump (56.32%), the number of panicles (65.38.5%), the number of fertile grains (58.71%), and yield in Kg/ha (45.09%). Additionally, a substantial increase in the number of infertile grains from the control (30 infertile grains) to the experimental plots (58 infertile grains) was observed. The harmful effects of these weeds warrant further confirmation during the rainy season, and incorporating the findings into rice production practices would help improve rice yields.
Issaka et al. (Fri,) studied this question.