Weed species composition and diversity of 2-year-old oil palm tree/fruit vegetables intercrop in rainforest zone of Nigeria

The spacing pattern and growth habit of juvenile oil palm during the early stages of field establishment have often led to serious weed problem until canopy closure at subsequent years. This study was carried out during the rainy season of 2016 to evaluate the weed species composition and diversity of an intercrop between 2-year-old oil palm tree and two fruit vegetables at an oil palm plantation in Ala, Akure-North Local Government, Ondo state, Nigeria. Two accessions of tomato (NGB 01665 and NG/AA/SEP/09/053) and eggplant (NGB 01737) were intercropped within the alley of immature oil palm. Weed sampling was carried out using 0.25 m2 quadrat within each experimental plot. Quantitative analysis of weed species parameters and Simpsons Diversity Index were evaluated. The result revealed that 28, 21 and 20 weed species were found across all the plots at 3, 6 weeks after intercropping (WAI), and after harvesting respectively. Members of Asteraceae produced the highest weed species at 3 WAI (17.857%); Poaceae recorded the highest weed species at 6 WAI and after harvesting (19.048% and 20%) respectively. A total of 23, 16 and 15 broadleaves were found at 3 and 6 WAI, and after harvesting. In all the juvenile oil palm/vegetable intercrops evaluated, the control plot recorded the highest weed species richness at 6 WAI, when compared to other intercropping regimes. The control and juvenile oil palm/tomato (NGB 01665) intercrop plot recorded the highest and lowest Simpsons Indices of Diversity at 6 WAI (0.877 and 0.734) respectively.