Abstract:
Field experiments were carried out in the 2015 (late) and 2016 (early) cropping seasons in Ado - Ekiti, in the forest-savanna transition eco-zone of southwestern Nigeria (Lat. 70 31' N, Long. 70 49' S; 730 m above sea level), to evaluate the effects of selected mulch materials on weed control and okra [Albemoschus esculentus (L.) moench] performance. Air-dried Calopogonium mucunoides (CALMU), Chromolaena odorata (CHROD), Panicum maximum (PANMA), Aspilia africana (ASPAF), Pennisetum purpureum (PENPU), and Tectona grandis (TECGR) leaves were each applied at 15 t/ha in a Randomized Complete Block Design experiment, using three replicates per treatment. Unmulched plots were included as control treatment to make a total of six treatments. Okra (Abelmoschus esculentus) was maintained at one plant/hill spaced 60 x 30 cm. Weed samples were collected from two 20 x 25 cm quadrates in each plot at 2, 4, 6 and 8 weeks after treatment (WAT) for the determination weed flora composition by taxa and growth habit. Data recorded on weed density and frequency of occurrence were used for the determination of weed control efficiency (WCE), weed species diversity (H') and weed relative importance value (RIV) as appropriate. The Asteraceae, Poaceae and Cyperaceae dominated the late-season site while Poaceae and Asteraceae dominated the early-season site. Annual broad leaves, followed by perennial broad leaves and annual grasses were the dominant weed growth forms in both cropping seasons. The most important weed across treatments in the late season was Urena lobata while A. africana was the most important in early season. Averaged over time, TECGR mulch exhibited a distinctly higher WCE, followed by ASPAF and CALMU mulch in the late season, and only TECGR mulch in the early season. Also, the highest weed density recorded in CALMU and CHROD mulched plots in both season is due to their fast decomposition and quickly release of nutrient after decomposition enhanced greater weed emergence. Crop growth parameters, pod
yield and nutrient contents were also recorded. TECGR controlled weed emergence most distinctly (P < 0.05) over time, especially in the late season, followed by ASPAF and CALMU. Generally, okra exhibited better shoot growth in mulched plots than in the control plots in both seasons. Residue mulching did not significantly (P > 0.05) influence pod diameter and fresh weight in the late cropping season. TECGR mulch was superior in almost all the yield parameters, except in pod weight and length. Also, in the early cropping season, mulching did not significantly affect pod fresh weight/plant. TECGR mulched plots produced the highest number of pods/plant and the highest pod fresh yield. Across the two planting seasons, the unmulched plots were better than other treatments with respect to edible pod length and pod diameter.
