Nursery professionals have discovered the benefits of managing weeds by topdressing containers with parboiled rice hulls — a weed management practice substantiated by USDA research. Scott Johnson, Commercial Director for Riceland Foods, discusses how nurseries can add parboiled rice hulls to their weed management toolbox.

How are PBH rice hulls used in the container nursery environment?

PBH rice hulls are used as a topdress material on field grown nursery containers to help prevent weed seed germination and growth. With a sufficient layer of PBH rice hulls on nursery containers, weed seeds are captured in the rice hull zone and are unable to reach the growing mix and make the seed-to-soil contact necessary to germinate and grow. It’s a simple process that works.

Are herbicide applications still needed?

Topdressing with PBH rice hulls can reduce or eliminate herbicide use. The fact that PBH rice hulls are a natural product and can help reduce phytotoxicity in herbicide-sensitive material is also important to know.

What makes PBH rice hulls valuable as a weed management method?

Using rice hulls to manage container weeds, including tough ones like liverwort, was actually developed by growers who were quick to recognize the benefits. Topdressing with rice hulls helps growers save labor by significantly reducing hand weeding. The use of rice hulls also provides the potential for less herbicide use. Minimizing damage to herbicide-sensitive plants and the possibility of reduced watering and drought stress also makes rice hulls a valuable product. Also important is that topdressing with PBH rice hulls costs only pennies per container, which can help reduce input costs and improve profit margins.

Photo courtesy of Riceland

How are the rice hulls applied and to what depth?

PBH rice hulls should be applied at potting, prior to watering, to a depth of one to two inches. The hulls can be applied by hand or with suitable topdress equipment. Our website ( also provides a downloadable topdress calculator. The product is available in compressed 50-pound bags or compressed 30-cubic-foot bales.

What type of research has been conducted on PBH rice hulls in nursery production?

Several years ago, Dr. James Altland, a research horticulturist with the USDA-ARS in Wooster, Ohio, began researching weed management options for herbicide-sensitive crops. He found that PBH rice hulls provide excellent control of bittercress and liverwort in containers. His research also found that oxalis seed placed on the rice hull topdressed container surface was still unable to germinate after six weeks.

How are PBH rice hulls processed?

PBH rice hulls are soaked in hot water, steamed under pressure and then dried. This sterilizes the hulls and renders any residual rice kernels, weed seeds or disease pathogens non-viable.

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