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How To Use Rice Hulls As a Soil Amendment, Mulch, Bokashi, Biochar, or For Composting

The rice industry has always tried to figure out applications for the use of rice hulls. Rice hulls are a waste product derived form the processing of rice into a usable form humans can eat. The rice hull covers the grain of rice, and acts as a protective covering during the growing season. It is composed of mostly silica, which in the gardening world can be a benefit for your plants.

As long as there has been large industry, there has been innovation with what to do with waste products derived from the processing of the industries main product. Luckily for us, the rice industry figured out many organic gardening uses for rice hulls to try to maximize their profits, and help to cut waste.

Some Agricultural Uses For Rice Hulls:
  • Soil Amendment
  • Compost Ingredient
  • Bokashi Base
  • Biochar Base
  • Mushroom Substrate
  • Animal Bedding

Using Rice Hulls As a Soil Amendment

Since rice hulls are comprised of mostly silica, they can be of great use as a soil amendment. Silica helps to strengthen your plants cell walls, and build up their immunity to things like drought and heat. Applying spray or fertigated silica products, can be costly, time consuming, and problematic on a large scale. With the addition of rice hulls into your soil, you will have a supply of silica that may last many years. In my own gardens, and container plants, I have seen rice hulls last 3 to 5 years before most has broken down. This makes rice hulls a very economical, low labor way of adding silica back into your soil that can lasts for many seasons to come.

Not only do rice hulls add back in silica to your soil, but they can also help to aerate compacted soils. By mixing in rice hulls to your soil, they will provide aeration similar to how perlite, or pumice would do in potting soil. In a garden, or field situation, you would typically do this every 2 or 3 seasons, as the aeration benefits should last multiple years. Depending on the microbial life in your soil, temps, humidity, crops being grown, etc.. you may be able to extend the length of time between incorporating rice hulls into your fields.

When used in potting soil, rice hulls are the perfect alternative to other aeration amendments like perlite. Unlike perlite, it will break down eventually, but again, I have seen it last 5+ years in living soil containers. We use it as part of our solution for long term aeration in our no-till living soil, and it has served us well for many years. If you are mixing your own soil for the season, rice hulls would be a great option for a single use soil. The reason I like it for single use soils, is that when you are done with the season you can compost the remaining soil, and there won't be any issues with perlite, pumice, lava rock, etc.. being in your compost. Then the next season you can use your old soil as compost for your new soil, and continue the cycle indefinitely.

Using Rice Hulls As Mulch In Your Garden or Flower Bed

Rice hulls can make a great mulch layer in your garden or flower bed. Unlike wood chips, shredded tires, lava rock, etc, you can easily incorporate it back into the soil to get added benefits the next season. The biggest down side I have seen with using rice hulls as a mulch is that when the wind blows hard, your rice hulls will go everywhere. Mixing your rice hulls with some compost to help give them some weight, and stability is what I would suggest when using them for a mulch layer. Even adding in 25% compost to the rice hulls mixed before hand can help you with keeping the hulls in their place. Also the addition of rice hulls and compost to your top soil layer will only benefit your flower beds or garden.

Composting With Rice Hulls

When I lived in Arkansas I got turned onto composted rice hulls because it was everywhere. There are some major rice producers in the Southeast part of the State, so rice hulls tend to be pretty cheap all over Arkansas. I remember being able to get a 16' trailer full of rice hulls for about $100 right down the road from where I lived. Since rice hulls are so prevalent there, tons of people, and companies compost them.

Depending on the time taken to compost the rice hulls, there may be noticeable rice hulls still in the compost, or it may just be all black and earthy. For my gardens I always leaned toward the partially broken down rice hulls compost with noticeable rice hulls still in it. This gave me the benefits of rice hulls, and the benefits of compost in one application.

If you want to compost rice hulls yourself you will need to properly mix them with a Nitrogen source as they are high in carbon. Things like grass clippings, plant waste from your garden, weeds, manure, etc.. can all be used to mix rice hulls with to aerobically compost them. Since rice hulls resist breaking down, it may take you longer than a standard compost pile to create a finished product. In warm places this will be less of an issue then say up in the mountains with a higher elevation, and shorter summer.

Turning Rice Hulls Into Bokashi

Bokashi is a shelf stable form of lactic acid bacteria serum, AKA LABS. LABS is known in the Korean Natural Farming circles to being a great all natural product that can help unlock nutrients contained in the soil. LABS does have a shelf life though, and this is where Bokashi comes into play. Bokashi is nothing more than a shelf stable form of LABS. You can create your own bokashi out of rice hulls, by spraying the rice hulls, and letting them dry completely before bagging. You may need to add some rice bran filler, or other ingredient to make sure the LABS properly turns into Bokashi, but I have made rice hull bokashi many times with nothing more than LABS and rice hulls.

Once it is properly made and dried, your Bokashi should be able to be stored for many years, and used season after season in your garden. It's a great way to turn a little bit of LABS into a lot of usable Bokashi. I will admit my first few tries at making it were not very successful, but be patient, and you can get to where you have a high percentage of success. `

Making Biochar Out Of Rice Hulls

Biochar is a long used product that originated in the Amazon. It has been made for thousands of years, and has shown to help maintain long term healthy soils. Through the process of pyrolysis, you can use rice hulls as a base for your biochar. It's not as easy as setting the rice hulls on fire, but with the proper equipment you can indeed make your own rice hull based biochar from home. After the initial pyrolysis, you will want to add in microbes either via mixing with compost, spraying with compost tea, or anything of the like. This finished soil amendment can then be used at a rate of up to 5% mixed into your garden beds, and potting soils. It gives the microbes a place to live, and we feel it is the key to a superior healthy soil.

As resources become finite on our planet, and consumerism continues to gobble up those limited resources, finding ways to use waste products, will be the key to helping our planet stay healthy. Rice hulls is one of the ultimate waste products that for you, the gardener, is cheap, effective, and has multi-faceted uses that your plants can benefit from while the planet benefits from less waste.
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