H. A. Akinnibosun

Ecological study of seasonal distribution of weeds in oil palm plantation at Agbarha-Otor, Ughelli North Local Government Area of Delta State, Nigeria, was carried out during therainyand dry seasons of 2020. Quadrats measuring 10 m2 were laid at random and informationontheweed species were gathered and used to generate diversity indices as well as other ecological statistics. During the dry season the taxa ranged from 27 - 50, individual abundance (376–2821), Dominance_D (0.1819 – 0.4248), Simpson index (0.5752 – 0.962), Shannon Wiener idex(1.469 – 3.468), Evenness index (0.132 - 0.7635), Brillouin (1.437 – 3.268), Menhinickindex(0.7073 – 2.116), Margalef index (3.569 – 6.914), Equitability (0.4301 – 0.9278), Fisher_alpha(4.705 – 8.632), Berger-Parker (0.07979 – 0.6424) and Chao-1 was (27.38 – 50.5). In termsofmost abundant species, density, relative density and importance index value in dry seasonindecreasing order were Poaceae > Selaginellaceae > Arecaceae > Melastomataceae>Bromeliaceae > Asteraceae. Diverse families in decreasing order were Poaceae > Asteraceae>Fabaceae = Rubiaceae = Malvaceae > Amaranthaceae = Connaraceae > Acanthaceae=Cyperaceae = Euphorbiaceae = Polypodiaceae = Tiliaceae = Gentianaceae with 7, 6, 5, 5, 5, 3, 3, 2, 2, 2, 2, 2 and 2 species respectively. While in the rainy season taxa ranged from32- 57, individuals (312 – 2178), Dominance, Simpson, Shannon Weiner, Evenness, Brillouin, Menhinick, Margalef and Equitability indices were (0.04491 – 0.4904; 0.5096 – 0.9551; 1.488–3.454; 0.10390 – 586; 1.426 – 3.284; 0.7037 – 2.887; 4.061 – 8.706) respectively. Equitability(0.4182 – 0.866), Fisher_alpha (5.373 – 17.31), Berger-Parker (0.1197 – 0.6944) and Chao-1were(32 – 62.08) respectively. In terms of most abundant species, density, relative densityandabstractimportance value index in rainy season, six weed families namely Poaceae, Asteraceae, Fabaceae, Malvaceae, Rubiaceae and Connaraceae were predominant. Similarly, the most diverse families in decreasing order were Poaceae > Asteraceae, = Fabaceae, > Rubiaceae, =Malvacee, > Connaraceae = Amaranthaceae, > Acanthaceae = Cyperaceae = Euphorbiaceae=Gentianaceae = Polypodiaceae = Tiliaceae with 7, 6, 6, 5, 5, 3, 3, 2, 2, 2, 2, 2 and 2speciesrespectively.The knowledge of weed flora will enable us to know the appropriate methodtoeliminate them from our agricultural farms to reduce competition with our valuable crops