Ep. 145 - Kitchen Waste as Plant Food: Egg Shells, Banana Peels, and Tea Bags, Oh My!

Karin Velez [00:00:01]:

This is positively farming media. Hello, my gardening friends, and welcome back to the just grow something podcast. When I first started gardening and eventually realized that our plants need to be fed with certain nutrients, I routinely used tums tablets as an amendment for my tomato plants to resolve blossom and rot. It made sense to me because blossom and rot, a result of a lack of calcium in the plant, and tums is calcium carbonate. So it was a cheap way to amend my tomatoes. Did it work? Well, anecdotally, yeah. I didn't have blossom end rot when I used the tums. I also started grinding the tums after I read that plant supplements needed to be water soluble. But from a scientific standpoint, was it really working, or were my tomatoes just not suffering lack of calcium to begin with? Eventually, I started using eggshells in the garden to thwart that blossom and rot. We raise chickens, and we always have a lot of eggshells. I ground the eggshells when using them directly with the plants, or I just added the eggshells to my compost pile and used that around the plants. Of course, this was all preventative, and I have no evidence that says that this is the reason my plants didn't have blossom and rot. And this is where we get garden advice that's not necessarily scientific. In nature, someone takes a bit of knowledge, like the fact that tomatoes need calcium, makes an assumption about how to do something. Okay, tums are calcium. Therefore, tomato plants can use tums and then make a correlation after seeing a result. I used tums. I had no blossom and rot. Therefore, tums solves blossom and rot. There are debates all the time about whether or not using eggshells or banana peels or spent tea bags or coffee grounds or any other kitchen waste as fertilizer in our home gardens is actually effective or if it's all anecdotal. So today we'll look at the science. Let's take actual scientific studies for each one of these garden amendments and find out whether or not crushed eggshells, soaked banana peels, or old tea bags and coffee grounds really do anything for our garden plants. Let's dig in.

Karin Velez [00:02:19]:

Hey, I'm Karin, and I started gardening 18 years ago in a small corner of my suburban backyard.

Karin Velez [00:02:24]:

When we moved to a five acre.

Karin Velez [00:02:26]:

Homestead, I expanded that garden to half an acre, and I found such joy and purpose in feeding my family and friends. This newfound love for digging in the dirt and providing for others prompted my husband and I to grow our small homestead into a 40 acre market farm. When I went back to school to get my degree in horticulture, I discovered there is so much power in food, and I want to share everything I've learned with as many people as possible. On this podcast, we explore crop information, soil health, pests and diseases, plant nutrition.

Karin Velez [00:02:54]:

Our own nutrition, and so much more.

Karin Velez [00:02:56]:

In the world of food and gardening. So grab your garden journal and a.

Karin Velez [00:03:00]:

Cup of coffee and get ready to just grow something.

Before we jump into the wonderful world of soil amendments, I want to welcome Anne as my newest patron over on Patreon. Anne has joined Patreon at the seed patron level and now has access to weekly additional content not shared anywhere else, including blog posts, videos and a quarterly discount code for the merch shop. If you'd like to join Anne in supporting this show monetarily each month starting at just $2, head to the link in this episode's description right there in your podcast player or go to Patreon.com justgrowsomething to see all the options and benefits. Thank you, Anne. I truly appreciate you.

So if you are into the science and you want to see all the resources for this episode, which definitely involves a lot of scientific journals and research papers, there will be links to all of these in the show notes. I always do list those resources, but this week there are a boatload of links to follow and rabbit holes to go down. So enjoy that if you're into it. Otherwise I'm just going to break it down Barney style for you here.

Okay, so the first thing that I want to say about this topic is that food waste going into our landfills is a huge problem and anything that we can do to divert that waste into something else, like compost or soil enhancers or amendments for our garden, I am all for it. But I also don't want us spending time needlessly transforming that food waste into something else if it's not going to benefit us in some way.

And you'll notice that I said soil enhancer and amendment since we're creating these at home and they likely will change in composition every single time we use them, there is no way to know what the actual level of nutrients is each time. So I would consider them more of an amendment than a specific fertilizer. But we generally know what each of the items typically contains in the way of minerals and other components. So the idea is the same. We're adding something to our soil that will in turn feed the plants and I think that's key here. Can you achieve results in the garden with chemical fertilizers? Yes, of course. Those fertilizers are intended to deliver soluble nutrients directly to the plants so they can take them up immediately. This will give a boost to the growth of the plant for as long as those fertilizer solutions remain, which means that they need to be continuously and consistently applied. The items we're talking about here are all natural biological items that may not necessarily be in a soluble form, but as they break down into that form, they feed the microbes in the soil and add their mass to the soil matter. And that's how the plants take up the nutrients. It has less of an immediate effect, but one that is much longer lasting. Now, there are things that we can do to make these nutrients more available to the plants much more quickly, rather than waiting for them to break down. This often involves making tea or emulsions, but we'll talk about that in a minute.

First, let's talk about the science. It is entirely feasible that the reason garden anecdotes are passed on is because there is some basis in truth, and that truth is based in science. Do bananas have potassium? Yes. Do our plants need potassium? Yes. Can we get that potassium locked in the banana peel, out of the peels and into the plant roots by burying banana peels in our garden or making a tea? Well, it turns out, yes. There have been studies using banana peels on everything from Swiss chard and tomatoes to potatoes and peas. And whether the banana peels were made into a compost, an extract, or simply dried and added to the soil, the results showed the banana peels made a difference in the growth of each of the treated plants compared to the control plants. Now, in the case of tomatoes, the germination rate and the subsequent seedling growth increased astronomically. In the shard, the height of the plant, the number of the leaves, and the subsequent yield were all enhanced. It increased the size of the plant in peas and increased the size of the pods and resulted in larger tubers in the potato harvest. What these different studies showed is that there is a number of minerals and nutrients available in the banana peel that becomes available to the plants once the peels are broken down. Not just the potassium. Iron, phosphorus, calcium, amino acid, citric acid, and proteins were all made available to the crops and likely work together in increasing the plant sizes and the harvest in the different ways that it did.

So how do we add our banana peels directly into the garden or into our potted plants, if we'd like to see faster results than our compost might give us? The easiest way that I saw in one of these studies was to just dry the peels in the sun, shred them up into small pieces, and add three tablespoons of the peels for every eight and a half pounds, or 4 soil. Easy peasy. One other interesting study I found showed that an aqueous solution, in other words, banana peel, tea, or a fermented solution, showed significant differences in the growth of hydroponic lettuces. So it's easy to see how that benefit could translate into our soil grown plants. And if this all seems like a lot of work and you don't necessarily need immediate results, you can just bury the banana peels directly in the garden bed. You can actually do this with all your compostable materials. We talked about that in the composting episodes. So, all in all, yes, banana peels will benefit your garden regardless of how you use them.

All right, so that's bananas. What about eggshells? This one seems to be a big point of contention in the gardening world. Some say absolutely use them. Others say it's a complete waste of time and don't bother who is right. Some of the funniest exchanges I have seen on the internet have come from the suggestion that you should bury a whole egg under your tomatoes when you plant them in the garden to prevent blossom and rock. Now, I know in my garden that that would probably just encourage the local raccoons to come and dig up my tomato plants as fast as they could to get to the eggs. But is there any wisdom in this advice? Well, maybe. Every study I've found has shown benefits of using eggshells in all kinds of different crops. But every one of those studies as using the eggshells in the same form. Eggshell Powder in studies using eggshells as a fertilizer, the shells were usually washed, dried and ground into a fine powder in a grinder. And this powder was used for the experiments. In one of the studies, the dried shells were made into a tea in addition to the powder. And the results showed the benefits of using the powder directly were significantly better than as a tea. Now, what type of results are we talking about here? In the case of potatoes, the plants were taller and they produced more large sized tubers. In peas, they produced more pods. In mustard, the plants were taller, the leaves were larger, and the yield increased over and over again. The ground eggshells were shown to increase the nutritional uptake of the plants and increase the plant health and overall yield. The conclusion in these studies is that calcium is a key component of the cell wall in plants. It's needed for enzyme formation, nitrate uptake, and root development. And it's possible that the organic calcium coming from the eggshells is able to be taken up by the plants more readily because soil calcium is often very immobile and it just doesn't make it to the plant roots. Now, this doesn't mean if you're using eggshells that you have to grind them into a powder to use them. You can just crush them and sprinkle them over the soil and they will eventually break down and release the calcium and the other minerals into the soil. It's just more effective when done as a powder. Heck, you can pour the water left over from boiling eggs out into the garden and you'll be adding the calcium that leached from the eggshells during the cooking process. It's all going to break down and be available eventually. The extra steps to break the shells down ahead of time are just going to make the nutrients available sooner.

And what about those tea leaves and the spent coffee grounds? Yep, there have been studies on those too. As far as the tea waste, the news is good for the garden. Tea leaves contain potassium, phosphorus, nitrogen and tanic acid, all important for plant growth. As the tea leaves decompose, they increase soil nutrients, which in turn promotes the activity of the beneficial microorganisms. It improves the soil oxygenation, which strengthens the root systems of the plants. The studies I found showed positive results in overall growth in the experimental plants compared to the control, and the tea leaves had just been dried and mixed right into the soil. No special preparations needed. Easy enough.

The news on the coffee grounds, though, isn't quite as clear cut. In fact, it's the only household waste item that I found that had such mixed results in different studies. There are many studies that concluded that coffee grounds are good for the soil and good for the plants, increasing plant growth and oftentimes helping to keep away peels like slugs. There are also experiments being done to reduce the amount of peat moss being used in potting soils by replacing some of it with spent coffee grounds. There were also some interesting studies where the coffee grounds increased the carbon levels in the soil and improved the soil aeration, but resulted in a decrease in plant growth. And then there were the studies that showed the spent coffee grounds being downright detrimental to the plants. One study grew broccoli, leeks, radishes, violas and sunflowers in three different types of soil with and without spent coffee grounds and fertilizer amendments. And all of the plants grew poorly in response to the coffee grounds. Another study used fertilizers created from spent coffee grounds and found them to be toxic to certain plants in certain soil types. So in looking at all the research, what I've gathered is that there are components of spent coffee grounds that may be toxic to soil microorganisms and plants, but at the same time, those toxins provide a natural pesticide and herbicide, and that much of this is dependent on when and how the coffee grounds are used. Everything points to using spent coffee grounds sparingly if used fresh, or composting them fully before use.

And that's what we do here. Coffee grounds go into the compost pile. In fact, everything goes into the compost pile the coffee, tea, banana peels, even the eggshells. I long ago stopped using tums or eggshells with my tomato plants. I just add all those components to my compost and add that to my soil. And I generally only have problems with blossom and rot when the weather wants to play games. So for most everything, it seems there are nuggets of truth for all these amendments. Dry the banana peels and the eggshells, grind them up and put them in your soil. Dump the tea leaves in there too, but maybe compost the coffee grounds before using those. All of these things are going to add essential nutrients to our garden soils and it will keep that kitchen waste out of the landfills, which is a win all around until next time, my gardening friends. Keep on cultivating that dream garden and we'll talk again soon.

Karin Velez [00:15:39]:

You just finished another episode of the Just Grow Something podcast. For more information about today's topic, go to Justgrowsomethingpodcast.com where you can find all the episodes, show notes, article courses, newsletter, sign up, and more.

Karin Velez [00:15:52]:

I'd also love for you to head.

Karin Velez [00:15:53]:

To Facebook and join our gardening community in the Just Grow Something Gardening Friends Facebook group. Until next time, my gardening friends keep learning and keep growing.