Parboiled Rice Hull Mulch in Containers Reduces Liverwort and Flexuous Bittercress Growth

Abstract

Use of preemergence herbicides for weed control is not always possible; some crops and many enclosed production sites are not labeled for herbicide applications. The objective of this research was to determine the utility of parboiled rice hull mulch for controlling two of the most common weeds in nursery crop production, flexuous bittercress (Cardamine flexuosa With.) and liverwort (Marchantia polymorpha L.). Two experiments were conducted to determine control of flexuous bittercress and liverwort with 0, 0.6, 1.3, or 2.5 cm (0, 0.25, 0.5, or 1.0 in) depths of rice hull mulch applied to the surface of 15 cm (6 in) diameter pots on a greenhouse bench. In both experiments, one group of containers were potted each with a single rose (Rosa ‘Radrazz’) and another group was not potted (only substrate and rice hull mulch). Flexuous bittercress seed and liverwort gemmae were applied to the surface of the substrate or mulch. Rose response and weed growth were monitored for 8 weeks in both experiments. Substrate pH, rose foliar color, and rose growth were not affected in either experiment. Flexuous bittercress and liverwort establishment and subsequent growth decreased with increasing rice hull depth. Containers with either a 1.3 or 2.5 cm (0.5 or 1.0 in) depth of rice hulls provided nearly 100% weed control. Rice hulls provided effective bittercress and liverwort control for 8 weeks with no adverse effects on roses.

Effect of Substrate Stratification Without Fine Pine Bark Particles on Growth of Common Nursery Weed Species and Container-grown Ornamental Species

“…Similar results were reported in the previous study where the growth of liverwort was <1% in all stratified substrates (Khamare et al, 2022). Liverwort is known to be sensitive to cultural conditions, such as moisture levels and high fertility [i.e., nitrogen (Newby et al, 2007)], and research has shown that mulch and alternative fertilization methods, such as dibbling or subdressing can suppress liverwort growth and spread (Altland and Krause 2014;Svenson, 1998). As stratified substrates consisted of 1 to 2 inches of top substrate strata with low water-holding capacity and without any fertilizer, stratification would be an ideal strategy to help manage liverwort growth in nurseries because it eliminates two major factors that contribute toward its spread.…”

Mulching as a weed management tool in container plant production - review

“…The choice of mulch materials will significantly depend on their availability and cost based upon the region or area, and mulch that is available which can be obtained regularly and be of consistent quality. Several mulch materials, including pine bark, pine tree chips, wood chips, rice hulls, and newspaper, have been shown to have no negative impact on numerous ornamental plants (Lohr and Pearson-Mims, 2001;Richardson et al, 2008;Altland and Krause, 2014;Khamare et al, 2022c;Wilen et al, 1999). Depth of mulch can impact weed control success; research indicates that applying mulch at a depth of 2.5 to 5 cm to achieve efficient weed control while minimizing costs.…”

“…However, the most widely adopted non-chemical method in recent years is mulching. While mulching has been frequently employed in horticultural crop production and landscaping, recent research has shown their ability to manage weeds in container plant production (Altland and Krause, 2014;Marble et al, 2019;Saha et al, 2020;Poudel and Witcher, 2022). While sanitation and preventive measures such as scouting, using clean soil and sanitized containers, and sourcing weed-free liner sources represent the initial steps in every integrated weed management plan, mulching functions as the primary line of defense against weeds.…”

A Review of Common Liverwort Control Practices in Container Nurseries and Greenhouse Operations

“…According to Svenson (1997), fast-drying mulches such as hazelnut [european hazelnut (Corylus avellana)] shells, rice (Oryza sativa) hulls, and pumice on the container media surface can suppress common liverwort growth to some extent. Altland and Krause (2014) reported that top-dressing containers in the greenhouse with rice hull mulch can reduce common liverwort growth. Rice hulls applied at a depth of 0.6 cm showed 2.5% and 20% common liverwort coverage at 4 and 8 weeks after potting (WAP), respectively.…”

“…Inside greenhouses, ornamental crop canopies can produce enough shade on the container media surface to promote common liverwort growth (Svenson et al, 2001). Altland and Krause (2014) quantified how the canopy of containerized 'Radrazz' rose (Rosa sp.) influenced common liverwort growth.…”