PBH Nature’s Media Amendment is a uniquely processed rice hull product from Riceland Foods, Inc. with multiple uses in the greenhouse and nursery environment. In container nurseries, it has been used with much success to reduce weed germination. For pennies per container, growers can free up employees that used to spend lots of time hand weeding. PBH rice hulls do not absorb water, which makes them well-suited for container crops that require irrigation, even those with fertilizer piped in. They dry quickly after watering and resist decomposition. They have been proven to keep weeds like liverwort and bittercress at bay for up to 15 months, plenty of time for most container crops.
This weed control practice was developed by growers looking for a better way to manage container weeds, says Scott Johnson, commercial director with Riceland Foods Inc.
“When you topdress with rice hulls, you’re creating a barrier on top,” Johnson says. “As long as the weed seed cannot reach that media, it cannot get the seed to soil contact to germinate. Plus, there is not the moisture to sustain germination of the weed seed.”
The practice offers many benefits, but the primary reason growers have taken to topdressing with PBH rice hulls is to reduce costs. This includes reduced hand weeding labor cost, potential for using less herbicide – another major expense -- and minimizing damage to herbicide-sensitive plants. Also, it can reduce drought stress and the need for watering.
Researchers have tested PBH rice hulls as a container topdress. Dr. James Altland of USDA-ARS in Wooster, Ohio, has conducted several experiments measuring effectiveness of rice hulls in weed control. His research shows the rice hulls prevent weed germination, even when fertilizer is injected through the irrigation system.
Of course, PBH rice hulls can also be used to replace perlite as a container substrate. Many nurseries run greenhouse operations as well for propagation, and often use perlite in their growing mix.
Michael R. Evans of the Department of Horticulture at the University of Arkansas researched the use of parboiled fresh rice hulls as an alternative to perlite in horticultural substrates. In his research, Evans determined that incorporation of PBH rice hulls into Sphagnum peat-based substrates did not result in significant nitrogen tie-up, and parboiled fresh rice hulls were free of viable weed seed.
When incorporated into Sphagnum peat-based substrates, parboiled fresh rice hulls did not negatively impact the chemical properties of the substrate. In fact, parboiled fresh rice hulls provided equivalent or higher levels of drainage and air-filled pore space than perlite. Finally, Evans found that root and shoot growth was similar for plants grown in Sphagnum peat-based substrates amended with equivalent amounts of perlite or parboiled fresh rice hulls. Click here to read more about the use of PBH rice hulls as a substrate.
Tom Demaline, owner of Willoway Nurseries, Avon, Ohio, uses PBH Nature’s Media Amendment as both a container topdress and a media amendment.
“PBH gives us weed control from day one,” he says.
Willoway Nurseries has been able to reduce labor costs associated with hand weeding, which were quite substantial for a grower with four million containers in production.
“We topdress containers with PBH at potting to ensure season-long weed control and significantly reduce hand weeding,” Demaline says. “With increasing labor costs and unpredictable weather patterns, we were looking for just such a tool to supplement our herbicide program. We also use PBH in our mix to maintain porosity. It works two ways for us.”
Hernie Rosado, production manager at Ridge Manor Nurseries is another believer in the system.
“Topdressing with PBH rice hulls has been a game changer for our weed control program,” he says.
Ridge Manor Nurseries is a wholesale grower located in Madison, Ohio. Rosado’s team offers a full line of shrubs, perennials, grasses and trees in various container sizes. He says the tangible benefits of using rice hulls are very real, especially for large growers.
“By topdressing with PBH at potting we save time, reduce hand weeding and use less herbicide,” Rosado says. “Those are three big benefits for a nursery with thousands of containers in production.”
To maximize efficiency, containers should be topdressed with rice hulls at the time of potting. This should be the last stop in the process prior to watering. The rice hulls can be applied to the container surface by hand or with a topdressing machine suitable for this application.
The Riceland parboiled rice hull product, PBH Nature’s Media Amendment, is highly compressed when packaged in your choice of a 50-lb. standard bag or a 30-cu.-ft. bulk bale. This lowers freight costs, generates less waste and minimizes storage and handling.
The hulls themselves are is a natural by-product of rice and considered a renewable resource with much to offer greenhouse growers, nurserymen, consumers and the environment. PBH is OMRI Listed® and WSDA registered.
For more information: http://www.riceland.com/pages/rice-hull-products/
The USDA-ARS in Wooster, Ohio, has begun a new five-year research program to develop weed management options for herbicide-sensitive crops. This is a multi-pronged approach to develop a wide variety of tools for weed control in production settings where herbicides are either not labeled or cannot be used safely.
A very promising part of this project thus far has been the use of parboiled rice hulls as a mulch in containers. Riceland Foods, Inc. has been marketing their parboiled rice hulls for weed management in horticulture crops, and some nursery producers in Ohio have already successfully used rice hulls for weed control. The goal of our research was to determine, in controlled research, what quantity of rice hulls provided effective weed control of liverwort (Marchantia polymporpha) and bittercress (Cardamine exuosa).
A Few Basic Points
Before I get into the details of our experiments and results, it’s important to review some basic concepts on how mulches provide weed control. Seeds of container weeds are small, and must germinate on or near the container substrate surface. When you cover the substrate surface with mulch, small weed seeds don’t have enough stored energy to grow through the mulch and establish themselves on the surface. This is primarily how mulches provide weed control, at least temporarily. The problem is that most mulches don’t provide long-term weed control because the mulch itself becomes an excellent substrate for weed germination. After the mulch is applied, new weed seeds that land on the surface of the mulch will soon germinate in the mulch itself. A truly effective mulch, especially for container production, is one that persists for a long period of time and offers an inhospitable site for weed seed germination.
Effective mulches for container crops should have a combination of the following properties: they provide little or no available nutrients, they dry quickly after irrigation, and they resist decomposition. Weed seeds require available nutrients to establish successfully. They may germinate in the absence of nutrients, but they will fail to develop much past the cotyledon stage without sufficient nutrition.
It almost goes without saying that mulches must resist decomposition. If the mulch decomposes, the barrier is lost and weeds are free to germinate. Unfortunately, abundant fertilization and irrigation are conducive to organic matter decomposition. The nature of nursery and greenhouse crop production renders many mulch products unacceptable due to decomposition after just a few weeks in production. To review, the ideal mulch will be low in nutrient composition, retain little water even after irrigation, and resist decomposition. With that in mind, let’s look at some recent experiments to see how effective rice hulls are in preventing liverwort and bittercress establishment, two of the most problematic weeds in nursery production.
Will fertilizers affect rice hull mulch?
The first experiment we conducted examined bittercress and liverwort growth in containers with 0, ¼, ½, and 1 inch of rice hulls applied to the surface. We filled 48 containers with standard greenhouse growing substrate and applied each rice hull treatment (mulch depth) to 12 containers. Of the 12 containers, six were placed on a bench that received overhead irrigation with regular tap water twice daily, and six were placed on a bench that received overhead irrigation with a standard commercial water-soluble fertilizer injected (100 ppm N) twice daily. We applied liverwort gemmae (spores) to the surface of the container weekly to encourage liverwort establishment. We applied bittercress seed to the surface twice, immediately after applying the mulch and about 4 weeks later. We observed weed control in the pots to determine if rice hulls could prevent these weeds from establishing.
Rice hulls at ½ or 1-inch depth provided 100 percent weed control. No weeds grew in these pots. In containers with ¼ inch of rice hulls, both bittercress and liverwort grew, albeit a lot less than the un-mulched pots. This may have something to do with the way we applied the rice hulls. For the 1-inch mulch depth, we carefully weighed the containers before and after applying rice hulls to a depth of 1 inch. The weight of rice hulls in those pots was 44 g. So, for the pots receiving ½ inch of rice hulls, we simply weighed 22 g of rice hulls for each pot, and 11 g for the ¼ in pots. This seemed a fair, consistent, and accurate way to meter out the rice hulls. In doing this, we observed that ½ and 1-inch treatments were completely and thoroughly covered with rice hulls. However, the ¼ inch depth left some gaps in the mulch layer so that you could see the substrate surface through the mulch. Invariably, it was in these gaps that liverwort and bittercress found a footing and successfully established.
Photo: shows oxalis seed (in red circles) on the rice hull topdressed container surface, still unable to germinate after six weeks.
Based on our earlier discussion on the role of nutrition in weed seedling establishment, you might expect weed growth to be more vigorous on the bench with fertilizer injected into the irrigation stream. And you’d be correct, that’s exactly what happened. Weeds in the non-mulched pots (no rice hulls) that received fertilizer were a lot larger than those in the control pots with no fertilizer. However, to my surprise, rice hulls applied at ½ or 1-inch depth provided perfect liverwort and bittercress control even with fertilizer injected into the irrigation stream. Quite frankly, this surprised me a great deal. I was expecting weeds to germinate into the rice hulls as long as fertilizer was applied via the irrigation system. But they never did in the 8-week trial.
After observing this trial for several weeks, I was impressed with how quickly the rice hulls dried following irrigation. Since nitrogen was not limiting in these pots, I concluded that it must have been the water that was limiting. Perhaps the rice hulls dry too quickly for weed seed to successfully germinate and establish? We didn’t have any sensors or fancy gadgets to measure moisture levels in the rice hulls. However, we irrigated all these pots twice daily, and we could see with our own eyes how quickly the rice hulls dried after irrigation. We could also see the weed seed and liverwort gemmae (reproductive spores) sitting on the surface of the rice hulls without ever germinating or establishing.
Research and photos provided by Dr. James Altland, Research Horticulturist with the USDA-ARS in Wooster, OH. He can be reached by email at firstname.lastname@example.org. Mention of any commercial product in this article is for educational purposes only, and should not be considered an endorsement by USDA-ARS.
Ronald Valentin has been named director of technical business at BioWorks, home to the RootShield, BotaniGard, BotryStop, CEASE, Molt-X, MilStop, NemaShield, PreFence and SuffOil-X brands of biopesticides and Verdanta and ON-Gard brands of biofertilizers. In his new position, Valentin will be increasing BioWorks ability to deliver personalized programs and support to BioWorks customers in North America.
Valentin has over 20 years of sales and support experience in biological control, working closely with growers to set up sustainable and effective pest management programs. He previously held positions at Bioline AgroSciences, Biobest, Foliera and Koppert. With experience training and managing technical support teams in Europe, Canada and the United States, Valentin has become a recognized knowledge leader among growers and a sought after writer and speaker.
"Ronald is an exciting addition to the BioWorks team," said Bill Foster, CEO of BioWorks. "His experience and customer focus will make significant contributions to our ability to serve customers."
Valentin can be reached at (289) 213-6787 or by email at email@example.com
Columbus, Ohio – The 2019 AmericanHort HortScholars program is now accepting applications through March 1, 2019, from students in horticulture-related degree programs of any degree level. Students wishing to apply may do so online at AmericanHort.org/Scholars.
HortScholars is a seven-day program that sets students in horticulture on a path to success by exposing them to the breadth of the horticulture industry, its opportunities, and its leaders at the industry’s leading trade show – Cultivate. The program offers a beyond-the-classroom experience, insight and awareness of the industry, and professional development via education sessions, networking, and working with industry mentors.
In 2018, AmericanHort received a record number of applications from students across the nation in top-level horticulture programs. Each year, the student’s applications show passions as vast as the horticulture industry. HortScholars’ majors have ranged from Horticultural Plant Production to Sustainable Plant Systems and from Landscape Architecture to Genetics.
Why should you become a HortScholar? To spend seven days in Columbus, Ohio prior to and during Cultivate’19 with paid-for meals, lodging, and an all-access pass to Cultivate, as well as a one-year membership with AmericanHort. HortScholars experience the behind-the-scenes logistics of readying the Columbus Convention Center for Cultivate and have exclusive opportunities for in-depth discussions with industry leaders, including the AmericanHort Board of Directors. These meetings provide HortScholars with insights into the industry and valuable contacts for their professional networks moving forward in their careers.
Daniel Greenwell, a 2017 HortScholar, highly recommends the program. “The HortScholars program connected us with important figures in the industry which helped me build my confidence in networking with new people. More important than anything, in my fellow 2017 HortScholars, I gained five amazing new friends and peers from very diverse backgrounds that I would never have met otherwise.” Daniel has now graduated and gone on to become the Horticulture Program Director at Piedmont Technical College.
Interested in applying? Simply visit AmericanHort.org/Scholars to complete your application by March 1, 2019. AmericanHort’s GenerationNext Community Connectors will evaluate the applications, then choose twelve finalists who will provide a short video on why they want to be a HortScholar. The six 2019 HortScholars will be chosen from those finalists. “HortScholar alumni have become valued members of the horticulture industry,” AmericanHort VP of marketing & member engagement, Mary Beth Cowardin says. “Whether they are running their own business, making new strides in crucial research, or pushing the limits of how horticulture products are marketed and shared, HortScholar alumni are the upcoming movers and shakers of the horticulture industry.”
Questions about the 2019 HortScholars Program? Contact Katie Gustafson at KatieG@AmerianHort.org for more information.
Check out our video interviews with the 2018 HortScholars: