Grit Experiment

pjames(8/LA)April 2, 2010

After having read discussions on the subject,. I've decided to do a test to see if grit has an actual benefit.

I divided a bin of EF's, not by actual count or eight but by approximate handfuls so there may be a slight variation but not much. I separated the worms from the castings then divided the castings and fresher bedding on top making each as equal as possible. They were put into the same size kitty litter buckets and allowed to acclimate for a few days.

While they were acclimating I made about 1/2 gallon of shredded newspaper and coffee grounds that I innoculated with some castings and allowed it to 'brew' for 4 days. This made a fairly wet pulp. For grit I used some of the clay I have in my soil here. It has a fairly small grit size.

Yesterday, I put a cup of the paper/coffee pulp with another cup of ucg's on top of the existing bedding in each bin. I then layered with a few inches of fresh dry shredded paper and cardboard and another layer of pulp and more fresh grounds. I did this 3 times then covered with more fresh bedding. The only difference was a liberal application of 1/2 cup of the clay grit in one of the bins.

I have no intention of disturbing either bin. I may need to add a little water if I do not see a little condensation in the bins. If I do, I'll pour in the same amount of water into each bin. My plan is to let the worms work undisturbed for at least two months without the addition of any food or bedding. I'll open the cover every few days to see if there are any noticeable changes in level.

I know there are a few variables I did not address but I think I started each bin as close to identical as I could.

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The equalness of the two bins for experimental purposes seems fine to me. Because I had read that Kelly had posted worms do not need grit, I did not add any. But then you, or someone posted they saw a big difference. A good reason to test. I wish you had access to sand to be one of the tests in addition to clay. I add a bit of biochar. I wonder if that acts as grit. Maybe people add grit because of the grit added to chicken feed because worms have gizzards like chickens and thus extended the thought. I would say worms do not need grit but then somebody saw a difference. If your experments show I should add clay then I will.

    Bookmark   April 3, 2010 at 3:08AM
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I'd read those same posts. Somebody claimed a commercial grower began to add grit . I personally do not think the difference will be significant. I owned a pet store for years and raised alot of cockatiels and even exhibition budgerigars for a time. I gave them no grit and they did fine.

Bur I did not want my own thoughts to prejudice the results so I set up the study the way I did. I could not tell you which bin is the one with the clay. Both look the same from the top. By the time I carried them back into the house and put them in place I'd forgotten. Even hefting them doesn't tell much- a cup and 1/2 of clay in a bucket does not make much difference.

    Bookmark   April 3, 2010 at 8:49AM
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I've also read a number of times that the worms need some sand or soil added. In my last bin (towards the end) I added some sand. Within a couple days, the whole top layer of cardboard was covered with castings (which weren't there before) and the level of bedding had gone down, so I assumed it was because of the added grit. With my new bin I've now also added some sand. Thing is, I've also got 10-20 times more worms (1,000-2,0000), than I started off with (100) 4 months ago. So I probably won't be able to know whether it's the sand or the worms that's making the difference.


    Bookmark   April 3, 2010 at 11:42AM
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One week update (and to keep the thread on the first page)

I had to add a coffee cup of water to each bin. The bedding was a little too dry on top and no condensation was seen. Over the past week the level of both bins has dropped equally-about 2 inches.

I did notice an error in my original post where I said I added a 1/2 cup of grit. That should have read a 1/2 cup of grit in each of the three layers for a total of 1 and 1/2 cups.

    Bookmark   April 9, 2010 at 9:53AM
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leearnold(z5 In.)

Wow, That's an awful LOT of grit! I use about 1/4 C. of fine sand per tote full.

    Bookmark   April 9, 2010 at 9:16PM
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Yeah, i wanted to make sure there was enough to see if grit really made a difference or not.

    Bookmark   April 9, 2010 at 10:28PM
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Two week update. I have resisted disturbing either of my test bins. (Something that is VERY hard to do). I have however added a little food to the very surface. I put a cup of red beans (Louisiana red beans and rice is spicy and has sausage most of the time)that was going out to the compost.And today I added a cup of UCG. the idea was entice worms tot he surface to see if any changes would be noticeable.

So far I have observed a pretty much equal drop in the overall volume of each bin. The only difference has been grit falling out the bottom of one of the bins. I attribute this to movement of the worms through the bedding. If a worm had ingested the grit, it would have been incorporated into castings and held in the bedding rather than dropping out the bottom.

    Bookmark   April 16, 2010 at 8:48PM
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Thanks for the update. I love experiments with worms!

    Bookmark   April 16, 2010 at 10:42PM
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Nice stuff pjames.

Keeps us informed.

Nothing like your own experiments to lay to rest common mis-information.

What have you got to lose?


    Bookmark   April 18, 2010 at 1:00AM
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leearnold(z5 In.)

Well, I can tell you my experience. I'm a long time wormer. I have about 20 bins. The worms WILL do fine, consume the bedding and food, and reproduce WITOUT any grit. BUT, They will do ALL that much faster WITH SOME GRIT! I use about 1/4 - 1/3 C. fine sand per batch of bedding that I mix up. I also include UCG in my bedding mix. That's what has worked for me.

    Bookmark   April 20, 2010 at 4:44PM
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OK, so how much is one batch?

    Bookmark   April 20, 2010 at 7:39PM
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Do you have to have sand as grit? I've put half-crushed eggshells, did the best I could, 3 year old manure that was pretty fine and UCG. Do I need to and some sand on top of that?

    Bookmark   April 20, 2010 at 8:02PM
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Three week update.
Well, I broke down and went digging into each bin to see what was going on. The top 3 inches looked like undisturbed bedding, but now more compressed than what I had originally put in the bins. Below that was a mixture of vermicompost and bedding. Most of the worms were living towards the bottom.

I made 2 major observations.

a. A large number of adults worms and eggs but no juveniles. (Which confirms i di d good job separating small worms and coccooons when I set up the test.

b. I can see no discernible difference in the amount of actual castings. The grit is either way too small to be effective (which I doubt) or it really doesn't play that large a part in the process.

I will continue to watch the bins.

    Bookmark   April 23, 2010 at 5:21PM
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Cough. Couldn't we cut into a wild caught worm and see if there is any grit in the gizzard? Cough.

    Bookmark   April 24, 2010 at 12:02AM
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Sure...only what is ingested depends on where the worm happens to be. I thought of cutting a worm from one of my bins but then I don't have a microscope to really differentiate the contents.

My main concern was if the addition of grit really added to the digestion process. So far I do not see much indication it has a pronounced effect. I suspect particle size of the available food may be a more important factor, which is why composted/partially predigested foods are observed to be processed more quickly.

    Bookmark   April 24, 2010 at 9:06AM
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Hi All; The grit that worms get the most use from is as fine as talc powder and is used primarly to grind the outer cell membrain (prokaryotes) of microbes and organic materials. It is so fine it would take a fairly powerful microscope to see it. The grit found in fowl is really thousands of times larger. So in the end the gizzard performs the same funtion as a humans mouth in the processing of food it masticates it.

    Bookmark   April 24, 2010 at 2:15PM
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"fairly powerful microscope" Got One I think. Maybe a Scanning electron microscope if I'm lucky. What Mag? And what does a gizzard look like so I can harvest a few. And what is the best way to ship to said microscope? And how do I get rid of the other stuff so the grit is left to photograph? If I let it rot on a tilted slide and drop water on it will the edibles drift away while the grit stays?

But still Kelly said grit was not necessary for composting worms. She was right about everything else. I doubt she said it with out scientific studies to back it up.

It would be so easy and fun to add grit and feel like I was doing something good for the worms.

But maybe I could just dawn a grass skirt and dance around and please them just as much.

Thus is why I am so grateful a person is doing an actual experiment to attempt to determine this. Then we can debate to death the details of how the experiment was conducted until each of those details are also experimented with. And replicated by non afiliated parties.

Until then my poor worms will remain gritless of the sand yards away from them but rich in biochar. Which somebody mentioned once will save the world and I totally believed with no scientific proof at all.

    Bookmark   April 25, 2010 at 2:13AM
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I think it is about time to terminate the project. I will wait until the end of the week ( 1 month instead of the 2 I had intended). I simply see no discernible difference in the amount of bedding consumed by the 2 groups. That being said, there may be a 20 to 25% difference that can not be determined by casual observation. That would require a fair amount of sifting and weighing.

The only thing I did notice about was NOT a difference, Each bin is healthy and has only adults and coccoons but no new hatchling or juvenile worms. That is because i had harvested the VC at the beginning of the experiment and used fresh bedding for the study.

Good for a study, but bad for me as I inadvertently put the juveniles and coccoons into my E. hortensis bin so now I have a mixed colony.

    Bookmark   April 25, 2010 at 6:57PM
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Your concluding statement to your experiment would be?

And how do we reply to all those zillions of posters that cheerfully post they add sand, or grit, or something to help worm gizzards do their jobs? I hate to be mean to well meaning posters but unsubstantiated fact is still unsubstantiated fact no matter how many times they post it as true fact repeating what they have read many places online.

    Bookmark   April 26, 2010 at 2:15AM
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If you don't mind, take the castings from the non-grit bucket and wash it all away to see if any grit is left.

I am always finding grit in mine, and it seems to be more than it should be.

I haven't used coffee grounds, any chance they have a gritty quality?

    Bookmark   April 26, 2010 at 3:52AM
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Hi All; Earthworms are nearly perfact in their evolution to date (someone elses observation)D. Brian Paleys. They have all the parts to make them efficent in the work they do. It makes no difference if you can tell if grit helps the worm or not in a managed bin. In natural environment the worm swallows grit, they even seek it out. Lts have been studied guite closly (the most studied species) and their foraging habits noted. If you do not believe the documented facts your worms are the ones that suffer your practices. I know from first hand knowledge how difficult it is to masticate food as a human with no teeth or a good fitting set of dentures. I will give my worms all the grit they will consume to help them get the most benifit from all the things they eat microbes and bits of vegative matter.

    Bookmark   April 26, 2010 at 8:50AM
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Hi! I'm a newbie who purchased a Worm Cafe a month ago and have been reading as much as I can for the past month about how to best care for my worms. I think it would be interesting to find out just what size of grit the worms actually use. I put in a little horticultural sand, but frankly I think the size is probably too big for the worm to use. Seems like it would be like swallowing a boulder!

However, I was thinking that the sand, even though of no immediate use to the worms, would actually help the texture of the final vermicompost to be more friable.

    Bookmark   April 26, 2010 at 1:22PM
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I decided to join the grit experiment. Since I am an avid pool player(notice I said avid,not good)I took a well used cube of cue chalk and scraped it onto one location in one tray. I'll let you know how they like it. Maybe they will turn blue.

Dave Nelson

    Bookmark   April 26, 2010 at 6:40PM
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I'm relatively new to this. I started last fall with an 18 gal rubbermaid with 1,000 worms and a 32 gal with 2,0000 worms. The 18 gal was 3/4 full and ready to harvest in March. The 32 gal wasn't going well. As I think back, I used dirt mixed in the bedding in the 18 gal and only coffee grounds in the 32. I now have about 8 bins going and I am soaking the shredded paper in water I let leaves soak in (hoping it helps break down the paper faster and I put a good amount of sand/dirt/coffee grounds. My 2 cents.


    Bookmark   April 27, 2010 at 6:21PM
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Jim said "As I think back, I used dirt mixed in the bedding in the 18 gal and only coffee grounds in the 32."

This does not surprise as you INNOCULATED the 18 gal bin with bacteria that gave the bin a tremendous headstart. The other bin had to catchup with whatever bacteria from the worms. I have found like most others here that using a little "casting tea" is a great way to really stimulate the decomp process.

Now that being said, I started this thread and experiment to see if I could demonstrate that kind of 'significant' difference in the reducing paper to usable castings. My now one month project does NOT show that difference.

I have read the arguments that people have said that worms have no teeth and they have a gizzard so grit MUST be an asset if not a requirement.

I want to point out something that most people here may not be aware of- in commercial poultry industry, grit is NOT used. In an egg production facility, chickens are kept in cages where they would have NO way to get grit. Some broiler production houses have concrete floors that can be thoroughly cleaned between batches of birds to reduce disease transmission. Now if grit would help these birds' efficiency even by a fraction, the money savings would translate into big bucks. Don't you think grit would be incorporated into their diet?

    Bookmark   April 28, 2010 at 10:53AM
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Hi pjames; The Egg farms here in upstate New York Ledge Farms and a couple others I know of put oyster shell grit into the mixed feed they give their chickens for two reasons one is it works in the gizzard and two it supplies the calcium used in egg shell production in the chicken. They sell the eggs to Egglands Best Distributors. I buy direct from the farm usually the Super Size double yoke eggs. At farm pick up is really quite inexpensive $1.25 a doz.

    Bookmark   April 28, 2010 at 5:32PM
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