“Greenhouse plant growers can substitute rice hulls for perlite in their media without the need for an increase in growth regulators, according to a Purdue University study.”
The above quote is from the link below.
Link: www.purdue.edu/newsroom/research/2010/101025LopezHulls.html
Thanks Henry for posting this!!! Chris Currey is a good friend that grew up in MN and did his BS and MS at the U of MN during the same time I did. We had our rented garden plots near each other. I had my roses and he had LOTS of vegetables.
Rice hulls sure are gaining in popularity as a media component. There is a local greenhouse grower that orders a whole bardge of it in up the Mississippi. This grower coordinates the order and it gets divided up among multiple growers.
A number of years ago a friend of mine working for one of the growers has some challenges with a rice hull product that was parboiled. The process releases some chemical that can sometimes be problematic, but if the lot is treated right shouldn’t be problematic. I forgot the details now. Dr. Jerry Cohen, a biochemist visited with my friend and I about it.
Has anyone found it as a media component in a common potting mix we can routinely purchase yet for home use out there at the garden center? It sure seems to help with good drainage from what I have seen for commercial production. That’s great that it isn’t binding up plant growth regulators for the commercial producers.
David
I wrote an essay a few months ago that included rice hulls. I was exploring “sustainable” resources as a substitute for soilless media that requires our limited resources created by geologic processes (vermiculite, perlite and pumice are the big 3). From what I recall, rice hulls were very good but the cons were that they do eventually degrade (durr, lol) and the sourcing is iffy, random and unreliable.
Lesson: look before you leap when it comes to rice hulls but they can pay off.
I also found photos of someone thatmade their home out of rice hulls but that is another story x_X Apparently thay make great insulation though, haha.
By the way, to any of ya’ll in hort. programs related to research/university, etc., I really do encourage this type of focus. It seems to be a hot, up and coming issue that could really be explored further. I had trouble finding enough factual, straight forward information to compare/constast within 16 pages. I was sort of bummed because it is definitely something that should be given critical thought for. I was also bummed that there were so few substitutions even though it is 2010. One of the main problems in the papers that I could find was that the information was mostly “green washed” or DIY fluff. The science was largely missing.
The horse farms aroung here use it for bedding because there is so much rice grown arond here and it is readily available and cheap. That should make some wonderful compost, but I don’t know if there are very many rice seeds in there.
Patrick
Kellogg’s AMEND and Black Gold Soil Conditioner have rice hulls as a component as does American Soil Products. The AMEND is just that-meant to amend heavy clay soils, too heavy to plant in directly, but a very good addition to soils that do not drain well. In So.Cal. we can get bagged rice hulls through tack supply stores, where it is sold as animal bedding, which in turn is then sold as a compost amendment(Craig’s list). I have used it as an amendment in high clay content soils with low organic content, and in my ‘homegrown’ organic soil mixes, but they have been generally to heavy for young potted roses. Here are a few suppliers.
http://www.americansoil.org/Products/tabid/63/categoryID/2/subCategoryID/3/projectID/3/Default.aspx
http://companydatabase.org/kw/rice-hulls
http://www.cvcshavings.com/products.htm
http://www.blackgold.bz/BG_past_articles/UseSoilConditioner.html
My Grandparents would use rice hulls in cymbidium potting mixes when they were growing blooms for export. I’ll have to ask my Grandmother why they used it.
California and the Phillipines are among the prime producers of rice, so location may play a huge role in the distrubtion and usage of the hulls.
I’ve had some experience with rice hulls used as stable bedding. The raw product doesn’t just drain: it sheds water. It’s also dusty. I am not a fan of the product in the stable or in the garden for just that reason. I’d be surprised if it acted as a reservoir for nutrients or water. Composted rice hulls as stable bedding made inferior compost. One problem was appearance: rice hulls are pale cream and stand out in the garden. Another problem was that rice hulls are so small that the compost doesn’t aerate properly. Rice hulls seemed to break down more slowly than the wood shavings that are often used as bedding. Shavings absorb and hold moisture and make a better top dressing in the garden with better texture and better finished appearance.
Locally, Sun Land uses rice hulls in its bagged potting soil. It is close to the bottom of my list of bagged soil products. It drains like straight sand and sheds water. It’s really difficult to dampen. I give it a C- to a D+.
When I tried to investigate rice hulls I found one major commercial site in southern U.S. promoting them. But the key may be that they are parboiled, not plain. They go by the acronym of PBH. In the U.S. a lot of rice is precooked, so there’s a lot of PBH available. It is sterile, free of weed and rice seeds. I had been wondering why not wheat hulls, or straw, or remnants from making rolled oats (oat hulls or husks. It may come down to how threshing is done for different grains- where the chaff ends up. Rice is very high in silica, so perhaps that delays breakdown in potting mixes, and serves as source of this essential trace mineral. Hulls are high in manganese and can be toxic at low pH according to one source. Parboiling improves water-holding supposedly. Some cheaper products may use them as harvested, so that they are waterproof, and even toxic. Cass may be able to comment on that.
About 10 yrs ago, Kelloggs promoted rice hulls as a component of AMEND, for the purpose of promoting better drainage qualities in clay soil. I have not been able to particularly pick out the hulls (visually) in their mix, but they continue to promote this particular use to gardeners and landscapers. I do not have the Kellogg propaganda papers that we were handed out at a promotional seminar (could have been from the nursery I worked for, where we promoted and sold it in a buy 2 get one free campaign) but it continues to sell, and like I said above, it holds to much water for rose seedlings. I have found a coir mix to give much better aeration.
I love coconut coir as long as it is from a source without a detrimental amount of salts. I think that it is a pretty cool medium to use. It also make more sense to me to use the waste product of something already being harested than to use a natural product created by environmental and geologic process. Rice hulls is similar to coconut coir in its sustainability but I did feel that I would not be investing any energy into using it. Filbert shells are often used here in place of bark dust but they are not all that great and they do not have any use as drainage, water retention or an ammendment. Theyre a waste product but theyre extremely expensive and limited in usefulness. I hope more is explored in terms of reusable products for landscape/hort.
Rice hulls are a byproduct looking for a use to turn it into a profit center. I can see the utility of appropriate rice hulls in the greenhouse with heavy water use on plants of different ages and sizes in different sized containers. In the garden, it has limited utility with the local soils. There’s no shortage of silica or manganese. It can’t be used as a top dressing. I have read that rice grown in California is heavily dosed with pesticides. If I were growing seedlings, I’d want a certification.
We didn’t use a manufactured product in the barn. This was back in the late 90’s and early 2000’s. It was delivered by the tractor trailer load from the Central Valley. The raw product is completely non-absorbent. Here’s a sample claim: “the rice hull [is] not only resistant to water penetration and fungal decomposition, but also resistant to the best efforts of man to dispose of it.” I didn’t notice any impact in the garden other than very slow decomposition.
I seen piles of rice hulls bigger than houses, coffee beans four feet thick the area of football fields rain soaked rotting. Called down south about warehouses full of tainted tobacco, offered to take it off their hands but they preferred to spend 365 mil./year storage cost rather than give away. They finally hauled it out and burned it.
When I got home today, I took a stroll around the yard, and then it hit me—rice hulls are bring pressed into “biodegradable” plant pots. I had a few paper white daffodils about 3 yrs ago that I meant to plant out. I dug a hole, placed the pot in the hole and then forgot to go back and plant it. 3 yrs later the thing still has not biodegraded. The daffodils are dead as doornails. The following blurb from a sustainable universe site tells why. When I think of biodegradable and compostable, I don’t think of 5 yrs to break down. I also have a bunch of ‘really cute’ rice hull pressed pots from some organic herbs that are resisting break-down. This is almost the same life of some poly based products.
“Eco-Friendly Planters: all Natural, 100% Biodegradable and 100% Compostable. Made from Rice Hulls. Will last for years. As seen on Treehugger.com! Say good-bye to ugly plastic pots! Eco-friendly planters for sustainable living. These attractive planters are made of renewable grain husks and rice hulls and will last up to 5 years under normal use.”