[01] Okoh Thomas, Department of Botany, Joseph Sarwuan Tarka University, Makurdi, Makurdi, Nigeria. [02] Okekporo Efe Stephen, Department of Botany, Joseph Sarwuan Tarka University, Makurdi, Makurdi, Nigeria. [03] Esah Faith Agbenu, Department of Botany, Joseph Sarwuan Tarka University, Makurdi, Makurdi, Nigeria. [04] Godwin Tochukwu Christiana, Department of Botany, Joseph Sarwuan Tarka University, Makurdi, Makurdi, Nigeria.

A survey was conducted in maize and cassava farms at the Joseph Sarwuan Tarka University Makurdi research farm between 2018 and 2019 cropping seasons. The objective of the study was to identify the most important weed species and to determine their relative frequency, density, abundance and important value indices. A quantitative method was employed for the enumeration and identification of weed species. Quadrats were laid along transects and individual weed species in each quadrat was identified and counted. A total 484 plants belonging to 68 species and 22 families were sampled in the maize farms. The species with highest relative frequency (FrR,), Relative Density (DeR) and Relative Abundance (AbR) were Commelina benghalensis (0.55), Synederela nodiflora (8.47) and Setera babarta (10.94) respectively. Also, S. babarta had the highest Important Value Index (IVI; 18.84). The family value indices (FVI) were highest in Poaceae (114.22) and least in Fabaceae, Malvaceae, Scrophulariaceae and Caryophylaceae (1.41), respectively. A total of five hundred and fifty-five (555) individuals belonging to forty-one (41) species and fourteen (14) families were sampled in the cassava farms. Tridax procumbens has the highest FrR, (13.89), DeR (42.34), AbR (15.98), IVI (72.22), while Asteraceae had the highest FVI (129.8). The most abundant species include: T. procumbens, Vernoria cinerea, Bracharia lata, Tephrosia braceteolata, respectively. Variation in the species IVI and FVI in both farms suggests the possible ecological effects (shade, competitive ability) on the pastures by the individual crops on the farm. Results obtained from this study could be useful in creating a weed management programme and in making informed decision on choice of herbicides and directing research towards new or improved weed control measures.

Weed, Quadrats, Maize, Cassava, Importance Value Index, Family Value Index, Makurdi

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