Rice Hulls vs Perlite: Which One is Better?

  • By: CarlBroadbent
  • Time to read: 7 min.
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Nobody is doubting the effectiveness of perlite.

Seasoned gardeners and novice gardeners often pick perlite as their first choice for a soil amendment, but did you know there are other options?

Specifically a more environmentally friendly option; rice hulls. Between rice hulls and perlite, which is better?

From an economic, environmental, and ease of use standpoint, rice hulls are better. Both rice hulls and perlite have their disadvantages, but by the end of this article, you’ll see why we can look past the small disadvantages rice hulls have. 

Rice Hulls

Rice hulls are the thin casings on grains of rice, kind of like the husk of corn.

Are Rice Hulls Good For Potting Soil?
Rice Hulls

After the rice has been harvested, the hulls are removed, and often burned to remove the byproduct waste from the farm. 

That is until someone had the brilliant idea to repurpose this byproduct into something useful.

Now after being removed, the hulls are sterilized by being parboiled at high heat to kill any diseases. 

There are so many other reasons to choose rice hulls from now on. 

Environmental Impact

We’ll go over it soon, but perlite is a non-renewable resource that needs to be mined from the earth with heavy equipment.

Rice hulls for plants pros and cons
Rice hulls pros & cons

Taking a resource that can’t be renewed with machines that are adding carbon monoxide and nitrogen oxide into the air is quite the opposite of rice hulls. 

Rice hulls are a completely renewable resource. As long as there is rice being grown, there will be rice hull byproducts to be used.


Good to Know: They don’t need to be mined, and harvesting the hulls doesn’t disrupt ecosystems like peat does. 


What They Do For Your Plants

Rice hulls benefit your plants and gardens in so many ways.

They improve the texture of the soil, they add better drainage, they add silica, and they can be used as weed-fighting mulch! 

If you are adding rice hulls to your gardens, spread a 2-inch layer over your soil and then mix the rice hulls into the top 6-12 inches.

If you want to add rice hulls to your potted plants, add up to a 50 percent ratio of hulls to the soil. 

When rice hulls are mixed in, it helps loosen the soil. This gives the roots more space to grow, improves the drainage in the soil, and leaves plenty of space for oxygen.

All of these are incredibly important for plant growth. 

Rice hulls also add silica to the soil.

Silica is used to strengthen the cell walls in the plant, and it improves their immunity to diseases, drought, and heat. 


Key Takeaway: Spraying silica is usually expensive and time-consuming, but adding rice hulls to soil is inexpensive and quick. 


Disadvantages

There are two disadvantages to using rice hulls. 

The first disadvantage is they begin to decompose after a few years, and as they decompose, the soil compresses again.

Are Rice Hulls Good For Potting Soil as a mulch
Rice hulls mulch

You can solve this by adding more rice hulls to the soil. Adding more rice hulls once a year will help keep your soil from compressing. 

The other disadvantage to using rice hulls is they can cause a nitrogen deficiency.

Bacteria and microorganisms in the soil use nitrogen to break down any additives with high carbon content, such as rice hulls, leaving little to no nitrogen available to the plants. 


Have You Noticed: If you notice the leave are turning a pale yellow color, and the growth has slowed, you might need to add a nitrogen-rich fertilizer. 


Cost and Availability

Rice hulls aren’t as easy to find as perlite, but they can be found in specialty stores, some garden centers, and online. 

Average cost per lbs: $1/lbs.

Rice hulls are bought in bulk, usually 50lbs bags, for around $40 to $60. 

Perlite

Perlite is volcanic glass popcorn. 

Let me explain. When a volcano erupts, and lava hits the water, it cools rapidly, but it also traps water particles inside the glass.

Rice hulls vs perlite for plants tips
Rice hulls vs perlite for plants

This glass is mined and is then heated to 1,600 degrees F.

When it reaches this temperature, the water particles vaporize and expand, and it causes the glass to “pop” as popcorn would. 

When the glass “pops” it grows to over 10 times the size it was before.

The results are an extremely lightweight material with microscopic air compartments. 

What It Does For Your Plants

Perlite helps loosen soil, keeps the soil from compacting, and helps with water retention and water drainage. 

Hold on, that sounds counterproductive; it holds water and helps drain water? It’s not, and here’s why. 

The perlite is going to add bulk to your soil so it can’t compact. The space the perlite is providing will let the water drain through the soil.

If the soil is compacted, that water has no room to drain and will sit in the soil until it can finally work its way through the pot. This is what leads to root rot. 

And those microscopic air pockets?

They trap and hold water molecules as the water travels through the soil. The pockets aren’t large enough to hold lots of water, only a little bit.

As the soil dries out, it pulls the moisture from the perlite, where your plants can access it. 

If you don’t want to buy premade soil mixes, you can make your own. The ideal ratio when making your own blend for container plants is one part loam, one part peat, and part perlite. This gives the perfect amount of structure, drainage, water retention, and helps keep the soil from compacting. 

Perlite is also great for propagating!

Take a Ziploc bag and fill it with moistened perlite. When you have a cutting you want to root, place the end into the perlite up to a node.

Fill the bag with air and seal the bag. Keep it out of direct sunlight, and check it after three weeks.

Perlite Vs. Pumice
Perlite Vs. Pumice

Your cutting should have rooted and you can plant this cutting. 

Disadvantages

Mixing Perlite with the soil
Perlite soil mix

Perlite has a few disadvantages:

  1. The first disadvantage is how lightweight it is. While it is great for the soil, it can be blown away by the wind, or washed away in the rain. It is so lightweight that it floats in water, so if you use perlite in your outdoor gardens, any perlite on the surface will float away with any excess water. 
  1. Perlite can also cause respiratory and eye issues. When working with perlite you should always wear goggles and a mask or the dust can irritate your eyes or lungs. 
  1. The biggest disadvantage to using perlite is its environmental impact. Perlite is a nonrenewable source. We can’t manufacture more, we can only mine what is available. 

The mining and processing of perlite are also disastrous for the environment.

Perlite for plants pros and cons
Perlite pros & cons

The gases given off by the machines required to mine the perlite, and the amount of power needed to heat the perlite to 1600 degrees F are not the least bit environmentally friendly. 

Cost and Availability

Average cost per lbs: $5/lbs.

Perlite can easily be found in stores and online. It is sold in much smaller bags, and you can buy 2lbs for about $10.

Harris Premium Horticultural Perlite for Indoor Plants and Gardening, 8qt to Promote Root Growth and Soil Health

Best Overall

They both work extremely well for gardens, and choosing what works best was a hard call to make.

It ultimately came down to the difference in cost, how easy it is to use, and the impact on the environment. 

Rice hulls are a fraction of the cost of perlite, you don’t need to wear protective equipment to handle it, and it is a renewable material that used to be a waste product.

This is what makes Rice hulls better than perlite. 

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