Yes, you can have too much. If your radishes, squash, cucumbers or turnips taste bitter, your potassium and phosphorus levels are too high.

An old-school manure farmer once said that the same thing is true when the wind blows the corn over; if the soil is too rich, the corn doesn't have to form as many roots as usual. I don't know if this is true, or if this has another cause.

But I think it takes a while to get to that point, as the plants use some of the nutrients, and some are being washed away by rain and irrigation.

Sue

In theory you can have too much compost in your soil, but in practice I have never seen it. Basically as you said, the compost breaks down, so doesn't build up too much from year to year. And who ever has enough compost to overwhelm their existing soil?

You can add compost before you plant, or just put it around the plants if you have it later. I don't really scratch it in around plants if adding later, just use as a sort of nutritious mulch. The worms and rain and so on work it into the soil for you without worry about hurting the roots.

I didn't know that taste test trick re: phosphorus and potassium. Thank you for sharing that, Sue. I grow radishes all over the place and that will be something interesting to observe, if they taste different in my various raised beds with varying amounts of compost. I will have to sow some in my large tomato/eggplant/pepper bed that is almost completely compost.

Marcia

You can get too much organic matter in soil, take a look at a swamp and you will see that. Is it possible for the average gardener to put too much organic matter in their soil? Yes, but not very probable. You can easily get too much of the wrong thing in your soil however, adding a lot of manure and little of anything else so the nutrients in the manure, which are very water soluble, just wash out of the soil and are not held in places by the vegetative waste that also should be added.

Thanks everyone. I guess maybe I'll just do a soil test on my compost before I add it to the garden so I don't throw off the ratios. It really makes me wonder if adding compost at all is worth it since it seems to be more detrimental than anything according to belgianpup. Should I just use the compost elsewhere and not in my vegetable garden? I don't want to ruin my garden soil by adding compost thinking I'm doing something good for it and then finding out I'm poisoning my plants.

Whoa sfg newbie you are coming to the wrong conclusion. Here is a link that might help you.


John

Here is a link that might be useful: The more I read the more I get confused

I have never spoken to a gardener who made, or had, too much compost. Such people may exist, but I've never met one. If you're "sprinkling" your compost on your garden and "scratching" it in, you don't have enough compost. I pile mine on and fork it in, and I don't have enough either.

Compost is good stuff---and vegetables love it.
Most flowers (not all) love it, too.

If you're going to have a soil test done, you might consider having your soil tested, not your compost. I ask for organic recommendations from the extension service, which gives me results I can understand.

I have never heard of the bitter taste of vegetables being caused by compost. No person here has recommended that you do not use compost in your garden. Most all knowledgeable gardeners would agree that compost is good for the soil and your vegetable plants. You can incorporate compost into your soil when you prepare you plot for planting. And you can top or side dress your plants with compost when they are growing. The only limitation that I see is that you should not grow veggies in pure compost. Most plants need some mineral soil to grow well. I would recommend fifteen percent compost in the soil where you plant and then sprinkle a little on top throughout the growing season. You may want to checkout the tomato or vegetable gardening forum to verify that most use compost for best results. PLEASE do not give up on using compost.
Bill Hill

It really makes me wonder if adding compost at all is worth it since it seems to be more detrimental than anything according to belgianpup. Should I just use the compost elsewhere and not in my vegetable garden? I don't want to ruin my garden soil by adding compost thinking I'm doing something good for it and then finding out I'm poisoning my plants.

Like John said, WHOA! Talk about jumping off the wrong end of the pier and into the deep water!!!

You jumped to a WAY wrong conclusion here. Think about it. If you were correct then millions of us would be sitting with ruined gardens and poisoned plants. That simply isn't true.

The slim, rare, negative complications were way overstated but that was due to the way you phrased your question. So ignore them. As with all things in life, yes it is possible to have too much. Is it probable that you will ever have too much compost in your garden? Not in this lifetime unless your garden is a 3'x3' plot and your compost pile is 10x as big.

Dave

all this time i thought a swamp was toooo much water with poooor drainage
oh silly me its becuz theres tooooo much compst wow
its like havin tooo much to drink & yur not sober by mornin but postin anyway

As far as I am concerned there is nothing wrong with a swamp. (Though Its not necessarily a good place for a garden, it is a good place for plants that like wet feet.) Its doing exactly what it needs to do, for our environment.

Also, if you ever do find yourself in the extremely improbable position of having too much compost for your garden, you can send it to me, and I will dispose of it safely for you, at no charge.

Well, I guess I stirred something up unintentionally! Sorry!

Let me clarify a bit, I garden in 2 foot by 10 foot semi-raised beds (they're beds that I dug out about six inches deep and then have another six inches above ground so they're 12 inches deep - I sifted out the copious amounts of rocks and added peat moss to help the clay be more conducive to plant roots) so the surface area for incorporating compost is rather limited to sprinkling. I gathered that, under those circumstances, my already fertile New England soil would be fine being supplemented with compost, which I did this Spring with bagged lobster compost from Coast of Maine that I bought half off last fall since I had none of my own compost ready for the task.

I had my soil test done in October 2007 and the (abreviated version) results were:

pH - 4.7

Calcium - 1222 lbs/acre (below optimum)

Magnesium - 280 lbs/acre (above optimum)

Phosphorus - 38 lbs/acre (significantly above optimum)

Potassium - 112 lbs/acre (below optimum)

Estimated Total Lead: Low, typical background levels

Soil texture classification: sandy loam

Organic content classification: medium

Suggestions: Add calcitic lime in Spring and Fall, and nitrogen before planting in Spring

SFG Newbie,

IMO you can spread the compost you have on hand. As a matter of fact, you may not have enough for the size of your bed. As most have already stated, you will be hard-pressed to add too much compost at this time, seeing as this is your first time adding compost. I trust what has been said will be of some help...

Blutranes

Good soil test - wish mine was even close to that. Nothing a little lime and some more compost won't fix. ;)

Dave

What did you unintentionally stir up, sfg?

Discussion? Sorry you're sorry.

pH was 4.7 ????

Because it takes any type of lime other than hydrated lime (not something you really want to use in your garden) several months to make soil pH changes you do want to add that several months before you intend to grow crops in that space. That low pH (optimal for most plants is in the 6.2 to 6.8 range) could cause major problems with soil nutrient uptake.
For those that misunderstand what a swamp, a bog, a wetland, a fen, is it is someplace that, for many reasons large volumes of water accumulate before moving on. Because of that large volume of water organic matter also accumulates and undergoes anaerobic digestion and that material becomes peat moss. These places act also as filters, clearing pollutants from the water. You often find these swamps near the end of a stream or river where the water from that source spreads out over a wide area, although not all rivers or streams will have a swamp at the outlet. Because some people have no idea what the purpose of these swamps is those swamps will often be filled in so they can be put to better use, resulting in more pollution and the destruction of wildlife habitat.

sfg newbie,

I AM SORRY! I didn't notice your name, or I would have elaborated. I was just answering your question: was it possible to have too much?

I should have said, "Yes, it is, BUT..."

Too much manure and compost comes from YEARS of adding more of it than is being used by the plants. This is when potassium and phosphorus levels rise to the point of being detrimental to the crops.

In real life, everything you add to that manure and compost 'dilutes' it: the peat moss (practically no nutrients at all) and the native soil. Then your crops take out a certain amount. And the winter rains and spring snow melt removes more.

As far as I'm concerned, it's difficult to get enough compost, especially when a person keeps making MORE garden beds and has to ration the stuff.

Anyway, I'm sorry that I gave the wrong impression via a careless answer.

Sue

Here is a link that might be useful: THIS is too much manure for your garden

arwmommy - Actually, the 4.7 is correct. This was after I'd prepped the area, but before I added any ammendments such as lime, etc, but after incorporating the peat moss. I was waiting on the soil test before I added anything.

kimmsr - Yeah, yeah, I'm evil for using peat moss. You've told me before.

belgianpup - I'm sorry I overreacted, I was just so disappointed! But, thank you for clearing it up. And, thankfully, there are no CAFOs around here with giant piles of manure (just the standard small dairy farms that spread their manure on their corn fields) like in the picture.

I gather I probably won't have enough compost to kill my plants unless I import some, so I think I'll just stick with my own supply and see how things go.

I live in a city, and my apartment has a walled in patio, with a section that is dropped down about 6 inches. The previous tenant had filled the low area with what I assumed was "soil". On one part of the soil sits a compost bin which is completely full, and spills compost out the bottom, onto the garden.

The tenant told me that the previous year, he had had such great success with zucchini, tomatoes, and carrots, that I would be overrun with vegetables. I planted zucchini, peppers, tomatoes, and many types of herbs. None of the plants flowered, although the pepper plants appeared healthy. The herbs (save dill) all grew about 3 inches tall, and remained that size and turned yellow, now 3 months later.

I'm baffled that he was able to reap so much, and I picked absolutely zero fruit this summer. My first thought was 'too much compost?' It's true that I did not amend the soil, but come on, zero?!

There are many variable that might affect your yields but 'too much compost' is pretty low on the list of likely culprits. The way you describe it the compost is not even in the soil but just spilling over onto it a bit. You haven't said anything about the source of you plants, how or when they were planted, how close they were, how you watered them, the weather or your fertilising regime. All are more likely to affect your crops that excess compost. Some photos would help. And it would probably be best to start a new thread for advice, perhaps on the Vegetable Gardening Forum rather than here on Soil and Compost, since it is essentially a veg culture question.

I have a walled-in/fenced-in patio garden, and one problem I have is not enough sun. Sorry if this is an obvious suggestion, but lack of flowering and stunted herbs may be due to not enough sun.

Gotta wonder what the previous tenant was adding in terms of fertilizer, if any. Yellowing leaves, especially the older ones on the plant (near the bottom) can be a sign of nitrogen deficiency, so maybe all they needed was fertilizer.

Yellowing of plant leaves is the result of those leaves not making chlorophyll and that has numerous causes not simply a lack of Nitrogen. This link has been posted numerous times before but still has good information about plant chlorosis which is what yellowing leaves is called.

http://extension.illinois.edu/focus/index.cfm?problem=chlorosis

kimmq is kimmsr

Okay, lets say you add leaves, wood fines, compost and sulfur, bone meal and blood meal to your soil, maybe a bit of peat moss. Is there any type of agrigate that you can add to the soil also? The leaves, wood, compost and some Bone meal, sulfur and Blood meal during the growing season are normal, but, if anyone uses these organic things, some type of sand or aggregate should be mixed in. Not alot of it, unless there is alot of organic matter.

Why would soil need that? What if it was sandy to begin with?

I think there is some confusion here about soil aggregates. Soil aggregates - sometimes called "crumb" - form naturally in a healthy soil that is not regularly tilled (disrupting the soil structure) and which has plenty of organic matter available and fully developed soil biota. "Aggregates" in the form of sand or other minerals are not necessary soil amendments. It's a bizarre suggestion and I would discount it.

Yes, in that sense I would understand. Soil biota create structures of smaller particles aggregated together. Gluing them with humus, if you will. They then act like larger particles, so a clay soil can have properties more like silt. But of course they are formed in situ and not added.

The soil critters glue the soil aggregates together with bio-glue! Polysaccharides, to be exact. And fungal hyphae stitch them together too.

Clay particles, being exceedingly small and also a little bit electrostatically charged, help stick soil aggregates together with organic molecules. Sand particles can also be incorporated into aggregates, but it's more difficult because they are so huge and heavy compared to all the other components that go into soil aggregates, and they're not electrostatically "sticky". That's why it's such hard work to improve the water-holding capacity of naturally sandy soils, even if you diligently add and add and add organic material. Adding sand to soil is the very definition of counter-productive, for this reason - you're just making it harder for the soil to aggregate together.

Numerous problems can be caused by too much organic matter in soil, pollution of ground water from excess nutrients leaching out of the soil, excess Phosphorus build in that soil, excess soil Nitrogen, too much organic matter holding increase the water holding capacity of the soil that displaces the air that plant roots also need to uptake soil nutrients.

http://www.extension.umn.edu/agriculture/tillage/soil-management/soil-management-series/organic-matter-management/

kimmq is kimmsr

I meant if your soil wasn't sandy, but, I think that if I was worried my beds were too much compost I would add a few shovels full of loam from my yard enough to make a thin layer. I was just afraid of the too much OM and drainage not being that great. I likely would'nt need the loamy soil added, but it would'nt hurt, some people add it to their compost anyway.