Optimizing Weed Management in Polythene Nursery-raised Cashew (Anacardium occidentale L.) Seedlings: Implications for Seedling Morphology, Transplanting Vigour and Soil Fungal Community Structure

Abstract

Background: Weed management in nursery crop production is frequently neglected by farmers, posing a significant threat to seedling quality, growth and transplanting success. In cashew (Anacardium occidentale L.) nurseries, weeds compete aggressively with seedlings for light, nutrients and water, and may harbour pathogens detrimental to seedling health, yet the optimal manual weeding frequency remains inadequately defined. Aim: The study investigates the effects of varying manual weeding frequencies on cashew seedling morphology, transplanting vigour, root characteristics and soil fungal community structure. Study Design: A Completely randomized design (CRD) was adopted, having six treatments, each replicated three times: weed-free (WF), weedy-check (WC), once-weekly (1W), once-in-two-weeks (2W), once-in-three-weeks (3W) and once-in-four-weeks weeding (4W). Place and Duration of Study: The study was conducted at Akinyele Local Government Area, Ibadan, Oyo State for three months. Methodology: Cashew nut biotypes were sown in polybags (25 cm × 12.5 cm) with 2 mm-sieved topsoil. Morphological parameters were assessed biweekly from 1 MAS. Destructive sampling at 3 MAS was conducted. Seedling vigour was rated on a five-point scale at 12 WAS. Soil fungi were assessed using standard procedures. Results: WC recorded the smallest leaf area (31.39 cm²) at 12 WAS while 4W (45.77 cm²) was the largest. WC (2.8) recorded the lowest vigour. Tap root length was significantly greater in 2W (18.2 cm) than WC (14.6 cm). Peak weed density occurred at 2–4 WAS. Initial topsoil recorded the highest fungal CFU. Aspergillus niger and A. fumigatus were ubiquitous, while Fusarium oxysporum and Trichoderma viride varied with weeding frequency. Conclusion: The critical weed interference period was 2–4 WAS, beyond which cashew canopy development naturally suppressed weed regeneration. Weeding frequency selectively shaped soil fungal community composition. Once-in-four-weeks weeding is recommended as a practical, agronomically sound strategy sustaining acceptable seedling quality while minimizing nursery labour demands.