Impact of Rice Hull Mulch Depth on Emergence of Multiple Weed Species at Varying Growth Stages in Nursery Containers

Abstract Rice hull mulch is widely used in container plant production due to its availability and effectiveness. This study evaluated whether common nursery weed species can survive or emerge through rice hull mulch when already established at the time of mulch application. Seeds of four weed species were sown to reach either the cotyledon to 1-leaf, 1–2 leaf, or 2–4 leaf growth stages using staggered seeding dates. Once seedlings reached the target stages, containers were thinned to five seedlings each and mulched with rice hulls at depths of 0, 0.6, 1.3, 2.5, or 5 cm (equivalent to 0, 0.25, 0.5, 1, or 2 in). Results showed that mulch depths of 1.3 cm and greater significantly suppressed emergence and growth of flexuous bittercress ( Cardamine flexuosa ), creeping woodsorrel ( Oxalis corniculata ), eclipta ( Eclipta prostrata ), and longstalked phyllanthus ( Phyllanthus tenellus ). These effects were observed at both early (1–2 leaf) and more developed (2–4 leaf) stages of these four species., The most effective suppression occurred at 2.5 and 5 cm depths, demonstrating the potential of rice hull mulch to serve as a sustainable weed management strategy, even if small weed seedlings are present at the time of application. All rice hull depths effectively prevented growth of liverwort ( Marchantia polymorpha ). Species used in this study: eclipta ( Eclipta prostrata L.), liverwort ( Marchantia polymorpha L.), longstalked phyllanthus ( Phyllanthus tenellus Roxb.), flexuous bittercress ( Cardamine flexuosa With.), creeping woodsorrel ( Oxalis corniculata L.).