Study: Rice Hull Effect On PGRs Comparable To Perlite

Greenhouse 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.

Growing media for ornamental plants often consists of a soilless mix of peat and perlite, a processed mineral used to increase drainage. Growers also regularly use plant growth regulators to ensure consistent and desired plant characteristics such as height to meet market demands. Organic substitutes for perlite like tree bark have proven difficult because they absorb the plant-growth regulators and keep them from getting to the plants. Using bark requires a 25 percent increase in the volume of growth regulators applied.

"We were not sure whether rice hulls, as an organic component, would hold up the growth regulator," says Roberto Lopez, a Purdue assistant professor of horticulture and co-author of a “HortTechnology” paper that outlined the findings. "Testing showed that there were no differences in plants grown with rice hulls or perlite."

Pansies and calibrachoa were planted in an 80-20 mix of both peat and perlite and peat and rice hulls and then treated with several different growth regulators. The plants treated with and without growth regulators and grown in peat and perlite and peat and rice hulls had similar heights and stem lengths.

Finding a waste product to replace perlite could reduce the price of growing media because perlite must be mined and heat processed.

"It’s a really energy-intensive process and, because it’s a mineral, it’s non-renewable," says Chris Currey, a horticulture graduate student and co-author of the “HortTechnology” paper.

Rice hulls are an attractive option, Lopez says, because they can be easily transported on barges and rice growers in the South could increase profits by selling a traditional waste product.

"Often these rice hulls were being burned because there’s not a lot of other use for them," Lopez said.

Syngenta and Fine Americas funded the research. Lopez and Currey collaborated with Purdue research technician Diane Camberato and graduate student Ariana Torres.

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16 comments on “Study: Rice Hull Effect On PGRs Comparable To Perlite

  1. I worked with a large greenhouse (over 10 acres)that converted to rice hulls from perlite to be organic. The company that the greenhouse bought the rice hulls from changed the way they processed the rice hulls. This process change caused the rice hulls to break down prematurely which in turn caused the soil to rob nutrients from the plugs/plant. The nurtient deficiency caused extensive stunting and plant loss and wreaked havoc on plant quality/availability.
    I understand another greenhouse lost their entire plug crop of Mother’s Day annuals. Be very careful–test on a small scale. The greenhouse I worked with has converted back to perlite….

  2. Fresh par boiled rice hulls do not break down prematurely. Excessive starch content robs soils of nutrients-and this issue has been addressed. Rice hulls are composed of lignin fiber, carbon and silica. Clean fresh par boiled hulls do not cause nitrogen problems. Rice hulls hold water differently that perlite-drying on the surface quicker-and often fool waterers to water prematurely. Growers have been successful when new products are embraced and adapted to. Rice Hulls are not perlite, and vice-versa. All changes in growing media require some adjustment in growing practices.

  3. The problem was that the rice hull processor was NOT using fresh water each time. They were recycling the same old water which lead to the faster break down and other problem. This processor had ALWAYS used fresh water in the past and for “cost savings” changed to reusing the same water—know one knew or was notified….growers lost hundreds of thousands of dollars from this one change… I understand new products take adjustment but when processors do not tell you about changes they make it makes you VERY hesitant to change…..This is a quality/trust issue.

  4. Growers may be able to squeak by using rice hulls in “grow it up and push it out the door” production. Rice hull compatibility with PGRs is fine for the producers of plants who are looking to reduce costs and attempt to be more “earth friendly”, but plants do NOT do well long term in this media. My observation is that hanging baskets and container gardens planted in this media WILL FAIL by mid-summer. Pretty much anything that is grown in rice hull media that is not planted into real soil or a non rice hull soilless mix by the customer will also FAIL. Customers DO get angry and tell all of their friends and family about their experience. They DO blame the garden center who sold it to them. They DO NOT know nor care about the difference in media types and if they need to do anything “special” to keep their investment alive. All they know is that they wasted their money and eventually will give up on plants and spend their money elsewhere.

  5. Maybe your hanging baskets failed because you had too much porosity(drainage). What about the peat? Peat is the main water holding source in a mix. What about the wetting agent?. Rice hulls have been used for many years by many growers who produce quality crops. I don’t agree that plants don’t do well long term. I’ve seen too many successful crops. The rice hull media plants I bought at Lowe’s this Spring lasted all Summer and Fall. Mr. Frost is going to have to get them. Rethink before you react.

  6. I worked with a large greenhouse (over 10 acres)that converted to rice hulls from perlite to be organic. The company that the greenhouse bought the rice hulls from changed the way they processed the rice hulls. This process change caused the rice hulls to break down prematurely which in turn caused the soil to rob nutrients from the plugs/plant. The nurtient deficiency caused extensive stunting and plant loss and wreaked havoc on plant quality/availability.
    I understand another greenhouse lost their entire plug crop of Mother’s Day annuals. Be very careful–test on a small scale. The greenhouse I worked with has converted back to perlite….

  7. Fresh par boiled rice hulls do not break down prematurely. Excessive starch content robs soils of nutrients-and this issue has been addressed. Rice hulls are composed of lignin fiber, carbon and silica. Clean fresh par boiled hulls do not cause nitrogen problems. Rice hulls hold water differently that perlite-drying on the surface quicker-and often fool waterers to water prematurely. Growers have been successful when new products are embraced and adapted to. Rice Hulls are not perlite, and vice-versa. All changes in growing media require some adjustment in growing practices.

  8. The problem was that the rice hull processor was NOT using fresh water each time. They were recycling the same old water which lead to the faster break down and other problem. This processor had ALWAYS used fresh water in the past and for “cost savings” changed to reusing the same water—know one knew or was notified….growers lost hundreds of thousands of dollars from this one change… I understand new products take adjustment but when processors do not tell you about changes they make it makes you VERY hesitant to change…..This is a quality/trust issue.

  9. Growers may be able to squeak by using rice hulls in “grow it up and push it out the door” production. Rice hull compatibility with PGRs is fine for the producers of plants who are looking to reduce costs and attempt to be more “earth friendly”, but plants do NOT do well long term in this media. My observation is that hanging baskets and container gardens planted in this media WILL FAIL by mid-summer. Pretty much anything that is grown in rice hull media that is not planted into real soil or a non rice hull soilless mix by the customer will also FAIL. Customers DO get angry and tell all of their friends and family about their experience. They DO blame the garden center who sold it to them. They DO NOT know nor care about the difference in media types and if they need to do anything “special” to keep their investment alive. All they know is that they wasted their money and eventually will give up on plants and spend their money elsewhere.

  10. Maybe your hanging baskets failed because you had too much porosity(drainage). What about the peat? Peat is the main water holding source in a mix. What about the wetting agent?. Rice hulls have been used for many years by many growers who produce quality crops. I don’t agree that plants don’t do well long term. I’ve seen too many successful crops. The rice hull media plants I bought at Lowe’s this Spring lasted all Summer and Fall. Mr. Frost is going to have to get them. Rethink before you react.

  11. Wow I just purchased several bales of PBH. I hope this "recycled water" issue has been taken care of and the batch I purchased is from fresh stock. I plan on using it as a perlite replacement. Switching from peat to coir also. I Think the changeover will go smoothly as long as the PBH performs as advertised. Can either of you who actually know the details of the problem let me know which manufacturer and time frame we are talking about here please.

  12. Were working with a vertical gardening system that provides mechanical root anchorage and do not need the caking properties of Peat Moss. We would like to see information about accelerating nitrogen lock up / decomposition. And what is the max % of rice hulls we might be able to go with. A picture should help. http://www.facebook.com /the vertical eco garden or http://www.verticalecogarden.com

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