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.