Compost Tea has become a very popular topic. The following is a quote from Fine Gardening (ref 2):
Gardeners all know compost is terrific stuff. But there’s something even better than plain old compost, and that’s compost tea. As the name implies, compost tea is made by steeping compost in water. It’s used as either a foliar spray or a soil drench, depending on where your plant has problems.
Why go to the extra trouble of brewing, straining, and spraying a tea rather than just working compost into the soil? There are several reasons. First, compost tea makes the benefits of compost go farther. What’s more, when sprayed on the leaves, compost tea helps suppress foliar diseases, increases the amount of nutrients available to the plant, and speeds the breakdown of toxins. Using compost tea has even been shown to increase the nutritional quality and improve the flavor of vegetables. If you’ve been applying compost to your soil only in the traditional way, you’re missing out on a whole host of benefits.
Let’s look at the facts.
What is Compost Tea?
This seems like a simple question, but it’s not. There is no clear definition of compost. Compost can be made from a large variety of materials, and each compost is different. If you make tea from two different types of compost you will get two different types of tea.
The nutrient content of each type of compost tea will be different.
One of the reported benefits of compost tea are the ‘microbes’. If we assume this to be true then is it not important to know which microbes are in the tea? It certainly is. The problem is that unless you have a fairly sophisticated lab you won’t know this. Home gardeners have no way to know which microbes are in their tea.
The microbe content of each type of tea will be different.
Tea can be made in two very different ways; aerobically and anaerobically. The term aerobic means that the tea is made in the presence of oxygen; you usually bubble air through the tea as it is brewing (see picture above). When tea is made anaerobically, it is made without added oxygen. You simply let the smelly sludge sit in a pail. The method used to make the tea is very important because microbes tend to favor one or other of these living conditions. They either like living with oxygen present or they prefer less oxygen. So the method you use to create the tea is very important to determine the type of microbes in the tea.
Aerobic soil bacteria inhabit soils that contain a lot of air; the light fluffy type of soil we all know to be good for plants. Anaerobic soil bacteria tend to live in wet, compacted clay type soils where there is little oxygen present – not the kind of soils we want. So why is it that many recipes for compost tea use the anaerobic method? That makes no sense and I can’t explain it.
There is also something called manure tea which is the same as compost tea except it is made from manure.
Bokashi composting is something completely different and is described in detail in Bokashi Composting Myths.
What Are the Benefits of Compost Tea?
Proponents of compost tea ascribe a wide range of benefits – see the above quote from Fine Gardening.
One thing is clear to me. If a product or gardening technique does everything under the sun, it is always too good to be true. When it sounds like snake oil, it probably is snake oil! Run for the hills.
There are a few main benefits that would be worth discussing. Compost tea is claimed to provide:
- An increase in nutrients
- A decrease in diseases
- Additional microbes for the soil
A recent study compared AACT compost tea to using just compost and is described in Compost Tea – Does it Work?
Does Compost Tea Increase Nutrients?
To clarify the question it should be stated more clearly as; Does compost tea add more nutrients than compost alone? There is no doubt that compost tea adds nutrients. But does the process of making tea increase the level of nutrients compared to just using compost without brewing? If they both add the same amount of nutrients–why bother making tea?
If you think about it for 2 seconds you will realize that this is a silly notion. Think about what you are doing in making tea. You take a handful of compost and you put it in a bucket of water. Microbes take over and start digesting the compost.
Your original handful of compost had a certain amount of nitrogen, phosphorus and potassium. No matter what process you use, you will never increase the amount of these nutrients in a plastic bucket (except for some minor organics falling in an uncovered bucket). The microbes might breed and grow and digest things, but the total amount of nutrients remains the same. In fact it might actually be less since some of the nitrogen might be converted to ammonia which evaporates into the air.
What about the quoted statement above “compost tea makes the benefits of compost go farther “. The nutrient content (NPK fertilizer numbers) of say 500 ml of compost is 2.6 – 0.9 – 2 (average value for composted cattle manure; source Alberta Agriculture Department). If I now add this to a 5 gal pale (about 20 L), I still have the same ratio of nutrients, namely 2.6 – 0.9 – 24, but it is now diluted 40 times (500 ml to 20 L). The nutrient value of the tea is now 0.07 – 0.02 – 0.05. That is an extremely dilute fertilizer. For comparison human urine has a nutrient value of 11 – 1 – 2.5, that’s 160 times as much nitrogen as compost tea. Sure you can probably spread the tea over a larger area than a handful of compost, but if you do that the amount of nutrients added to the soil is negligible – so why bother??
The fact is that making tea from compost does not increase the amount of nutrients. It does not make the compost ‘go further’. If you want to add nutrients to the garden just add the compost directly.
In the post, Compost Tea NPK Values, I have a closer look at the NPK values and what manufacturers of the tea and kits for making tea have to say about their products.
Will Compost Tea Decrease Diseases?
This topic has been evaluated extensively, in reference #3 (link no longer valid). There are limited studies about disease reduction by compost tea, and the results are inconclusive.
The concept here is that the tea has a high concentration of microbes. When these are sprayed onto leaves they populate the surface of the leaves to such an extent that invading pathogenic microbes can’t take a hold. The good tea microbes out compete the potentially bad ones.
For this to work, the sprayed on microbes would need to colonize the leaves (ie live and breed on the leaves). This requires that the new environment, ie the leaf surface, has enough food for them and the oxygen levels are right for them.
Clearly, the oxygen levels would be high and so you can expect that anaerobic microbes would die out quickly. Anaerobic tea just won’t work.
The native microbes on plant surfaces are not well understood. There are anywhere from 1 to 10 million microbes on each 1 square centimeter of plant. Nobody knows what happens when more microbes are sprayed onto the leaf. I can’t help wondering why the large number of naturally occurring microbes can’t out compete the potentially bad ones and yet the ones sprayed on in the tea will do this??
In summary, there is little scientific evidence to support the idea that compost tea solves disease problems.
Does Compost Tea Add Microbes to the Soil?
There is no doubt this is true. You have a pail full of slimy microbes and if you spread it around the garden you are certainly adding microbes to the garden.
There is a new gardening trend of adding microbes to the soil under the assumption that the soil ‘needs microbes’. I’ve looked at this myth in more detail in the post Soil Microbes. In summary; the soil already has lots of microbes and adding a bit of tea is not going to make much of a difference.
If you are interested in identifying the microbes in tea you should read this before buying a microscope and taking Dr. Ingham’s course: Soil Bacteria – The Myth of Identification and Management.
The scientific study discussed in Compost Tea – Does it Work? clearly shows that adding microbes from AACT tea does not impact plant growth.
Can Compost Tea be Dangerous?
It is important to ask this question. Even if there are some minor benefits for using compost tea, they could be outweighed by risks.
Think about what you are doing when you make the tea. You are creating an incubator for microbes. You are providing the moisture, the food and the right oxygen levels to grow microbes. But which microbes are you growing? You have no idea know.
The reality is that along with the ‘good’ microbes you might also be growing ’harmful’ ones. You could be growing microbes that will make you or your plants sick. Tea that is aerated can contain Salmonella and E. coli both of which can prove to be deadly to humans. Remember the contaminated lettuce? That was E. coli contamination. You could also be growing microbes that are harmful to plants.
This study shows that adding molasses to increase the microbe populations can significantly increase the population of salmonella and E. Coli 0157.
The process for making compost tea is not selective – you grow whatever is in the pot.
I am confident that the risk is low. But why take the risk when the benefits of compost tea are at best, minimal?
Conclusion:
If you want to make some compost tea, go ahead. You will probably not harm anything and you just might have some fun doing it. But understand that there is currently no evidence that compost tea is any better than using just compost. Be a smart gardener and just spread the compost on the soil as a mulch. Nature will do the rest.
Further Comments:
This post now has quite a few comments. Many of them are from people with feelings about this topic but without any scientific evidence that their feelings are correct. If you have some references to discuss – please continue posting comments. If you have no valid references to support your position – don’t bother commenting, because I will not approve the comment.
For more information and explanations about the myths promoted by Dr. Ingham, have a look at these posts:
Teaming With Microbes – In Depth Book Review
Soil Bacteria – The Myth of Identification and Management
Teaming with Microbes – A Close Look, Part 1
Teaming with Microbes – A Close Look, Part 2
References:
1) Application of Two Microbial Teas Did Not Affect Collard or Spinach Yield: http://hortsci.ashspublications.org/content/44/1/73.full
2) Brewing Compost Tea : http://www.finegardening.com/how-to/articles/brewing-compost-tea.aspx
3) Link no longer valid.
4) Photo source for Aerated Compost Tea: Lily Rhoads
I myself love drinking tea, along with my breakfast in the morning, it’s nice get some random micro-nutrients and diverse flavors in.
I believe plants and soil are very similar, being as my vertical garden is enclosed, I used containers and I do brew compost tea.
Not everyone’s goal is tons of nutrients, too much of anything isn’t good, wouldnt you agree fragile mycorrhizal networks?
I hit use most of the herbs and flowers I grow up there, lots of moringa from my tree too, and if your concern is pathogens… I also have a neem tree which is most importantly anti-fungal, anti-microbial, and anti-parasitic.
When I water my plants I dont wanna flush all the nutrients away; as the pots are geared towards drainage, and I feed the top-dess/mulch flora, so compost tea is afforable, sustainable, and isnt chemical fetilizers that have extremely high transfomity tolls from start to finish…. especially if they’re made with petroleum or heavy metals!
My understanding of endo-phytic fungi also plays a role in this concoction, I also add some korean natural farming love, with my understaning of indigenous micro-organisms…IMO for short.
Clean minerals are also good, used what I used for for Spirulina cultivation.
Tons of applications for compost tea, did you know if you add spent mushroom mycelium blocks to a vortexed microbial brew, the microbes will make pre-digest the substrate so one can add it to their wom-bin? Like pre-biotics and pro-biotics, Gardenmyths.com
Lastly, my perception of what’s best for all things considered is always growing, this is a nice place for that, keep growing y’all!
The benefits of compost and compost tea are different and they are best used in combination. A farmer will use both ground and foliar application on their crops in a season. Compost is a slow release “fertiliser” and you can only be applied to the soil. It is widely believed that you put compost in the ground now for the next season’s crop. Making a compost tea means that you can apply the “soup” to the leaves in the same way as you would use a foliar spray, or as a drench (where it is also great as an activator for breaking down incorporated organic matter or mulching material). Bare in mind only when the microbe dies is the nutrient released.
Somehow, I think the author misses the point of compost teas in several key respects. Compost teas should be well-aerated, and should not be made from manures, which practically eliminates the possibility of E coli and Salmonella contamination. Compost teas of course do not add nutrients, and I have never heard a claim that they actually add nutrients. So it’s a straw man argument. Rather, compost teas are meant to increase nutrient availability from the interaction of the microbes and soil roots. What microbes are in compost tea, the author asks? Well, they are the same microbes that are in your quality compost, of course! And while you may not know the full suite of microbes in your compost (something that is in itself very difficult to determine), you can be 100% assured that those will be the microbes in a well-aerated tea, though likely in different proportions after 12 hours of tea-making. There are ways to make tea dominated by fungi (add ground oatmeal for example–I have done it) or dominated by bacteria by growing your tea from a well-decomposed, primarily “green” compost. In at least one reply, the author says he is speaking from “science”, not practical evidence. I don’t see much science in the discourse. Many people have had good experiences with compost teas, and while I agree that there needs to be more studies as to why, it is scientifically indisputable that teas multiply up the same aerobic organisms that are in the compost by many degrees of magnitude, provided that teas are properly aerated and nourished–which all quality teas should be, IMO. I work in the fertilizer industry, yet I fully appreciate that fertilizers alone are not enough. While the author states that soils are already full of microbes, many soils suffer from severe disruption of their microbial communities due to tillage, compaction, removal of crop residues, pesticides, and yes, even careless fertilizer use.
I suggest you spend more time researching this topic. Lots of people make compost tea without aeration and you can buy small packages of manure on line specifically for making compost tea.
Re:”compost teas are meant to increase nutrient availability from the interaction of the microbes and soil roots” – how exactly does this happen? You say that “Compost teas of course do not add nutrients”, so where do these nutrients come from? Microbes interacting with roots will not produce nutrients.
Re:”you can be 100% assured that those will be the microbes in a well-aerated tea” – I don’t fully agree with this statement since not all microbes will grow well in water, but lets say it is true. Why then would tea be better than just adding the compost to the soil? I never claimed tea would not be better than doing nothing. What I said it is not better than just adding the compost.
Re:”While the author states that soils are already full of microbes, many soils suffer from severe disruption of their microbial communities due to tillage, compaction, removal of crop residues, pesticides, and yes, even careless fertilizer use.” – that is true. But adding a cup full on microbes to the soil will not fix these problems. If the conditions are not suitable for natural microbe life, it will also not be suitable for microbes from tea or from compost.
Robert, regarding compost teas I think you are spot on. However, having read your post re planting by moon phase, I also think you are absolutely correct, except I doubt, as you claimed, that “true believers” (my emphasis) of moon phase planting had castrated you. Now, THAT would be terrible of them. Suspecting you are still, like Rex Tillersom, fully intact, might I suggest castigated? Lol.
It is an expression that should not be taken literally.
Hi Robert,
just based on Ms. Ingham’s claims and some logic (so no full scientific studies behind it), let me answer your questions.
1) “Where the nutrients come from?”
Answer is from the soil itself. An activated soil food-web is supposed to extract both, more nutriends from minerals and more nutrients from existing organic matter.
It is scientifically well established that many fungi help extracting at least P / increasing the area of which roots can “catch” that P.
And it’s also well established that specific bacteria types increase organic matter decomposition rates / the turnover rate. Think about wastewater sludge, that is veeeeery aggressive on pruning residues while doing industrial scale compost. An aereated compost tea fed with molases could be more or less the equivalent of that wastewater sludge: full of hungry bacteria, that attack the organic matter in the soil and thereby releasing the nutrient the O.M. holds.
Of course, this could have several side effects. But if the nutrients being released make the plant grow much more (=> more sugar to the soil via roots, and after that all the necromass) it could be worth it.
.
2) “Why not apply just compost?”
Well, besides from the already explained multiplying effect (on certain strains) of an areated brew, I would never think about applying compost tea in a back-yard garden for precisely that same reason. The main advantage I see is in compost tea that from a very small amount of compost you can make a huge amount of tea, so it’s more suited for larger farms where you can’t possibly get enough compost to fertilize everything.
.
3) “If conditions are not suitable, microbes will just die”
When I first read about compost tea, it claimed to be suited specially for farms transitioning from conventional to organic. So the inoculation occurs precisely in the moment of a management change that should help that micro-organisms thrive.
Anyhow, I’d like to recall the wastewater sludge comparison. While it might be true that all microorganisms end up dying, there is a transient effect. Microbes don’t just die off immediately: most of them will try to survive first. While active, they may mobilize important nutrients for the plant. Sugar released by the plant in exchange might help them survive for a while. And only after harvest go into a dormant form or just die away.
I’m also wondering if the high sugar content in the compost tea might be even more important than the bacteria itself. If the plant releases sugar from the roots in order to nourish the soil food web, wouldn’t the sugar in the tea also encourage a bacterial bloom?
In any case, timing would be essential under this perspective. Just as timing when applying fertilizer.
Of course, scientific studies should be conducted to test all this hypothesis.
Here an interesting study on the effects of different inoculants on soil biology. Of course it’s with very specific inoculants, not a broad compost tea of unknown composition. It does however show that dramatic changes in soil biology can happen by innoculation. Both, transient and long-term (and of course, no change at all).
Jumping to conclusions:
“Microbial inoculation may cause tremendous changes in the number and composition of the taxonomic groups. However, the observed impacts depend largely on the techniques used to address the dynamics of soil microbial communities. Some works showed no effect or a transient effect; however, others evidenced a long-term effect. These changes may influence plant and soil and thereby induce unpredictable feedback reactions. Effects on plant growth and protection are not necessarily resulting from a direct effect of the inoculated strain and may be related to induction or repression of resident microbial populations.”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3728534/
So, given the possibility of great changes by inoculation (so, addressing your point nº 3 “either they are there or they will die”), the question is whether or not compost teas (and the way they are applied) are a reliable way to change soil microorganisms for good. And if it’s a transient or a permanent change.
Comment #1 referred to the claim that compost tea has higher nutrients. This claim refers to levels before it is added to soil.
Comment #2, lets assume that adding a lot of microbes to soil improves the soil or nutrient levels in soil. You can easily brew microbes from all kinds of input material – you don’t need compost or manure. The comments here refer mostly to gardening.
But I think you re missing the point of adding compost directly. If the microbes will live in soil, then you only need to add a few and let them grow in the soil, instead of in a container. Adding a small amount of compost directly to soil, that is ready to support microbe growth will have the same effect as brewing it first. Except that it might take an extra 3 days for the microbes to grow.
Comment #3 – are there any studies that show an increase in available nutrients in soil after adding compost tea? The claim by the pro-tea people is not that they increase soil nutrient levels for a few hours while the microbes stay alive. Their belief is that this is a long term benefit but increase the microbe population in soil.
Try telling John Evans that compost tea doesn’t work! He holds about a dozen world records for vegetable growing size as well as hundreds upon hundreds of ribbons and badges from garden expos. Others who have tried his methods have had equally great results with their gardens. Given that there is an infinite number of methods and ingredients one could use to make compost tea, perhaps you have just not been using a method that works. Rather than casting doubt upon an entire movement/art of a growing method, maybe you should consider trying a different method than the one that you determined didn’t work.
You missed the point of the article. The conclusion is not based on the method I tried, it is based on what science has determined.
I really think you’re missing the point of compost tea. Compost tea or extract is nothing more than a cultured array of bacteria, yeast, protozoa and nematodes. The idea centers around the benefits the microflora in the soil have on plant health. You’d have to understand soil biology to understand the idea.
So if I use direct compost, there won’t be any bacteria, yeast, Protozoa and nematodes? Direct compost doesn’t benefit the microflora? Direct compost does not help soil biology?
Compost is full of bacteria, fungi, yeast and protozoa – not sure about nematodes – but if they are not in the compost, they will also not be in the tea. Compost benefits the microflora and soil biology and better than tea, since the compost not only contains the microbes it also contains a lot of undigested organic matter which the soil biology need as a food source.
One speck of good quality garden soil contains up to a billion bacteria.
I agree with you. I was merely being sarcastic to that post. It doesn’t make any sense to brew tea to culture bacteria, yeast etc.
There are two forms of brews from compost we might be confusing… compost tea is generally applied to the plant while compost extract is applied to the soil. The purpose of either is inoculation of microflora and the advantage over direct composting is the amount of compost needed to do the job. However… composting is very important as it does include organic matter while also supplying beneficial microflora. Understanding the role of microflora in the soil is critical in understanding its importance as there is a very complex symbiotic relationship going on. You might google “Elaine Ingham” and listen to some of her discussion on soil biology.
Re: “The purpose of either is inoculation of microflora and the advantage over direct composting is the amount of compost needed to do the job” – this is a common concept but it is false.
It is true that brewing tea will increase the number of microbes you apply to either plant or soil. However, the amount you apply is such a small fraction of the existing microbe population already on plants and in soil, that the increase is insignificant.
But let’s say the increase supplied by the tea is significant. Will the added microbes grow and prosper? No. If conditions were suitable for them to multiply, the native microbes would have already done that before you even started making the tea. Whatever the existing population is, its growth is limited by the environment it finds itself. Adding extra microbes to a population that has grown to its limit will not result in more microbes – only more dead microbes.
Be cautious when reading material from Dr. Ingham – much of it is not science based.
I also have yet to convinced of the value of tea, a very imprecise term, especially when applied to a well-made finished compost. Is that bubbling perhaps the nitrate reverting to N2? But neither have I found much value in waiting around for compost, except maybe for direct-seeded tap root crops. I’ve had great luck with soaked alfalfa pellets, to the point where I regretted buying the truck with which to haul “free” manure. Finally I settled on low-N casually composted non-conifer debris and sheep manure, for potassium, and enough alfalfa to make sure they have enough N, and bingo. Alfalfa alone has too much N to be the only fert for most crops. Now I use comfrey and broom green manures in addition to a mulch of autumn leaves, since our new location has so many maples.
Admittedly my tests have only been on my own garden at home but the results were plain to see. I have several citrus trees, blood orange, lime, lemon, grapefruit, and have constant issues with iron deficiency. I have had success using liquid iron supplements applied to the soil and as a foliar spray. I have been able to achieve comparable results with repeated applications of compost tea to the soil using all store bought ingredients–no specific sources of iron included. For years I had spread compost as a mulch around the plants and never saw a discernible effect. But with compost tea I could clearly see the symptoms of iron deficiency decrease. Obviously the tea had made the iron in the soil more available to the plants.
I have also done a fair amount of container gardening and in that context there is absolutely no substitute for compost tea. Typically when growing plants in containers there is a limited volume of space for watering and applying mulch. Personally I like to leave adequate space so I can give a large amount of water to the plant before it overflows the container–I loathe watering someone’s garden when they fill their pots right to the brim. With compost tea it is far easier to apply the beneficial microbes to containers than with solid compost.
Many of the gardens I work in are completely mulched with some sort of bark or wood chips which make applying compost as a mulch very time consuming and irritating as you have to pull back the decorative mulch from every plant you want to give compost to. Again, compost tea makes application so much easier. Applying compost mulch to a lawn is a pain but tea is easy.
I think their will always be variance in compost teas because that is the nature of life and that to request scientific data with broad implications will never give you the answers you seem to want. As there are no standards for compost tea you have many people doing many things differently. It is quite possible that some people know what they are doing while many do not. All my experiences with compost tea show that it is not something you can just apply once and expect to see amazing results–I have never seen this happen with compost as a mulch either. When I achieved my best results with organic gardening it was with compost tea applied every two to three weeks. Had I tried to apply compost mulch at the same rate I would have gone through quite a bit of compost, but with the tea I was able use a far smaller volume of physical material which I think is a win in terms of overall time and motion efficiency.
While I have my brew routine streamlined from start to cleanup and storage, I unfortunately see many people brewing in a manner that makes me cringe. Some people just let the compost sit in water for days and don’t aerate. Few take the time to understand the importance of feeding the tea but also not over-feeding–I don’t brew “fertilizer teas” but I do brew to help unlock and make accessible the nutrients in the soil or applied as powder/pellets. I see tea brewing in dirty containers with loads of bio-slime from previous brews–equipment must be kept clean! Perhaps the most common mistake I see is people using a tiny air pump to aerate a huge container of tea for far too many hours. It is important to understand the oxygen retention capabilities of water, how temperature affects this, and how populations of microbes can boom and bust during the brew.
Yes tea is more complicated but I enjoy the learning/experimenting process. I would argue that for the average gardener who just wants a nice garden that compost as a mulch is a better use of their time than futzing with tea. But for those who are interested in putting in the time and energy to see if they can give their plants an extra boost I think tea is great, and great fun.
The way you categorically dismiss tea is unfortunate since it is impossible to prove or disprove the benefits as there are far too many variables to draw broad sweeping conclusions. One cannot prove the existence or non-existence of god, but it works for some people.
You can just spread the compost right over the mulch. It is easy to apply.
I make steeped compost tea to use in places where adding full compost is not possible. ie. to plants growing in pots
Robert, thank you for the very interesting read. Thank you for keeping it scientific. Why there is never love for inconclusive evidence is troubling…speculation and anecdotal accounts are not replacements for empirical evidence; not when you earnestly seek a truth beyond your bias, desires, and best guesses.
My question is about bonemeal tea. I am wondering if you have any evidence or hypothesis on the effectiveness of hot brewed bonemeal tea? My hopes is to use it as an injected fertilizer for tomatoes. Typically, if added to the soil, bonemeal slow releases calcium (so I have read anyway). Tomato sometimes develops blossom end rot, which is said to be the cause of low calcium uptake by the plants (could mean low calcium in soil). This happened to me. In my case, I know that the calcium level in the soil is low (soil test). So, you see my interest in correcting the issue at once. The plants are under plastic mulch and are irrigated via drip tape lines. The irrigation system has an injector as well, which I intend to use to incorporate calcium via hot steeped bonemeal tea.
If you have low levels of calcium, use a soluble calcium source – not bonemeal. Calcium nitrate will dissolve easily and also add nitrogen. There are also liquid calcium fertilizers.
Blossom End Rot is a result of not enough calcium getting to the fruit – not the same thing as “uptake by plants”. Inconsistent watering is the usual culprit, but low calcium levels in soil can also cause it. Blossom End Rot
Very interesting stuff. Thank you. I had some zucchini which developed blossom end rot. They were near a Mugo Pine, which, I understand, creates acidic soil. I saved my washed egg-shells and blended them into a powder which I worked into the soil for the zucchini. No blossom end rot this year!
Consider getting my book – Garden Myths. all of the following myths are discussed in the book.
Evergreens do not make the soil acidic. Their needles are barely acidic and much less acidic than rain. Besides a more acidic soil will make more calcium available to plants.
Egg-shells do not compost, so they sit in the soil for ever, adding few nutrients.
Blossom End Rot is rarely a soil calcium deficiency – it is usually caused by irregular watering. If you did not see it this year egg shells had nothing to do with it.
I had a thought. I have a drum-style composter that I am trying. I’ve had to put a basin under it to collect the liquid that drips out of the seam. (It stains the patio bricks.) Can I dilute it and use it like compost tea? I’d rather not just dump it.
Yes – but it will add very little value to the garden. See my latest post, Compost Tea NPK Values.
More of a question than a comment. Granted tea may not actually do anything for the subsoil biome. Is it possible that brewing the tea and adding it back into the compost will speed up the breakdown of the material in the compost bin?
Probably not since a compost pile already has lots of microbes. It might have a limited effect if it is rich in nitrogen but most tea is mostly water.
Hey Robert, interesting article, I’m an indoor container gardener. What’s the best way to feed the plants during seedling/grow/flower? What should I use and at what ratio?
At seeding don’t use anything. Once you have seedlings use any cheap soluble fertilizer – something with more nitrogen, and less phosphorus – like 10-2-4. Most of the fertilizer will be washed out of the pot when you water so NPK ratio is not that important.