Also: What will happen if you leave compost too long?
Can too much compost kill plants?
Clumping of compost will happen when composting materials, that are prone to sticking together, roll around in a compost tumbler. Compost clumping can be avoided by adding more ‘brown’ material. This will keep the compost mixture more open from the beginning of the composting process.
Most people start loading kitchen waste into either a compost bin or compost tumbler and watch it gradually fill up. Then, after a while, they notice that everything in the bin or tumbler has consolidated into clumps.
The main reason for clumping of compost is compaction through settling. The material that you add to your compost bin will be wet or at least moist.
This will be especially so if your compost is to be made from mainly kitchen waste. Clumps will form when there is a build-up of one particular type of kitchen waste and nothing else in it to keep it open.
If your compost is clumping, don’t add more water
Clumping is inevitable from wet and heavy waste. It will sit there with more wet and heavy material being regularly loaded on top. The clumpy lumps are prevented from becoming compost because they become sealed within themselves.
These are stagnant clumpy lumps of wet organic material that air can’t penetrate. They may become mouldy on the outside, where the air can get at them but no moulding can happen in the middle.
Without the initial moulding process, the clumpy lumps in compost, will be effectively preserved. The clumps in compost tend to be acidic. A compost clump is effectively being ‘pickled’. If you have a compost bin that’s putting out a bad smell, one of the reasons will, most likely, be that clumping has occurred.
There are things that you can do to reduce clumping of compost.
When you feed waste to a compost bin the structure of the composting heap will form gradually; you may add small amounts of waste just once or twice in a week. You can reduce the instances of clumping if you add materials that will form a layer in between that which would form clumps.
For example, if you have just added a load of kitchen waste to the compost bin, add some shredded newspaper or pieces of ripped-up cardboard before adding any more kitchen waste.
Doing this is an easy way to stop clumping of the compost that you want to make. It will allow air to get at the kitchen waste material. The moulding stage can happen and allow the following stages that involve microbial life forms to take the composting process to the next stage.
It’s wise to build your compost pile in layers for reasons other than avoiding clumping. Kitchen waste tends to be high in nitrates and low in carbon. High nitrate material won’t rot so quickly if there is little or no carbon ‘brown’ material to create a balance.
Don’t forget hydrated white lime
Add a dusting of hydrated white lime when adding kitchen waste. This will reduce the risk of acidity. In some cases it may be possible to make compost by just adding white lime to kitchen waste and do without adding shredded paper. It will depend on the mixture of materials that make up your kitchen waste.
Introduce worms to make really good compost
The addition of worms can very often deal with the clumping problem. Worms will often find their way into a compost bin without doing anything to attract them. If there are no worms in your compost, get some and put them in. They will take up residence and work on all the material that hasn’t formed a clump.
They will eat the material on the outside of the clump, gradually breaking down the whole clump over time. After a while the worms will work their way into the clump and help to turn the whole thing into compost.
Compost clumping can happen in a tumbler bin
Some people have problems when trying to make compost in a tumbler. This is usually because of the same reasons that clumping happens in a static bin. If the mixture of material isn’t balanced, then clumps will form and they will stay as clumps even when you roll the tumbler over.
Clumps are more likely to be prominent in a compost tumbler. The rolling action will help to form clumps into almost spherical balls. They will become separated from the rest of the compost that’s formed. The rolling action is rarely enough to physically break up clumps.
The only thing that you can do is to intervene and break them up using a trowel or wooden stick. Once you’ve opened them up, the air can get in and the material in the clump will start to rot. The addition of hydrated white lime will definitely help at this stage.
The Rolypig compost tumbler rarely has problems with clumping. Because the Rolypig sits directly on the ground, worms find their way in and multiply to huge numbers. This means that every delivery of kitchen waste will get the attention of the, often, overflowing population of worms.
When the kitchen waste starts to go mouldy, the worms will consume the mould. As the material rots down, after the mould-stage, the worms will proceed to burrow into it and help to break it down further.
What will happen if you leave compost too long?
You have some compost, somewhere. It’s either in a compost bin waiting for you to do something with it, in a bag, away from the elements or it’s in a tidy heap, somewhere.
When compost reaches the stage where it’s ready to use, you may not be ready to use it. This is when you may feel like asking: what will happen if you leave compost too long? Will it go ‘off’ or lose any nutrient value that it once had?
If you leave compost for too long it will degenerate. There will be very little useable compost left. Nothing will happen to the microorganisms that break down organic material into compost, they will keep on going. Compost that’s been left, unused, for too long, will lose the nutrients that plants would make use of.
Think about what will happen when compost becomes compost. It starts as food or food bi products. If you discard this food material as bits that we don’t want, it will rot down into compost.
The compost making process doesn’t stop at a point that’s convenient for us. If you leave nature to do its thing, compost will continue to break down into a very fine, black crumb.
Compost can be stored in a plastic bag
If you have compost that is finished in terms of having broken down all food waste, you can store it in a plastic bag. Allow some ventilation in the bag. Generally, nothing more will happen to compost that’s been bagged and kept away from moisture.
Compost will dry out and become a preserved, dry crumb. If you can arrange for this to happen you will have compost that can be used as an organic fertilizer whenever you want it.
Compost on the ground will disappear
A compost heap that’s left out in the open on soil, will breakdown completely and vanish into the ground. This will be unavoidable. Being subjected to the elements of weather, a compost heap will be kept moist from either rain or whatever precipitation that can be drawn from the atmosphere.
With moisture there will be, continued, decomposition and worms. These will move in from the ground under the heap. They will keep working on the entire mass of the compost heap.
After a long period of time there will be nothing to show that there was a compost heap there, except that there may be a range of plants that have taken root. These will grow exceptionally well due to the volume of nutrients that will be in the ground.
Can too much compost kill plants?
Too much compost won’t kill plants but it may affect how they grow. Compost is a condensed source of nutrients. Too much compost will risk applying too much of a specific nutrient or range of nutrients, to plants. If plants have been over-fed with nutrients, they will grow taller but the plants’ structure will be weak.
Worm-cast compost is a different matter. Any plants that are rooted in just standard compost and nothing else, will behave differently. Plants need a balanced supply of nutrients. There are few, if any, plants that grow normally if there is an excess of a particular nutrient. Plants will grow if they are subjected to too much compost but they often grow taller than they otherwise would.
When plants are fed with too much of one nutrient and not enough of another, the plants’ structure is often compromised. When you see plants that look spindly and weak, this is usually due to the soil conditions.
Avoid too much compost and not enough soil
If there is no soil and plants are growing in just compost don’t be surprised if the plants look poor.
Listening to what others say, there are some who insist that too much compost will kill plants. There are occasions where this is possible. If it does happen, then, we have to ask: what other contributory-factors are there?
Don’t use too much compost that has chemical residues
We don’t always know what’s in the compost that we have. Some gardeners use chemical weed killer. The chemicals in weed killer will kill plants which then get put in the compost. Some of the chemicals in weed killer will break down and cause no problems.
There is a risk that some residues will survive and carry through to effect plants that we are trying to grow. Where this happens the instance of, what appears to be, too much compost killing plants, is not the effect of there being too much compost but the lingering effect of chemical residues.
This isn’t to say that any compost that has any trace of chemical residue will kill plants. Compost that’s mixed into soil and used as an organic fertilizer, could have small amounts of chemical residues that would kill plants if there was enough of it.
It’s possible for plants to be subjected to chemical residues and survive. It’s only when plants receive a large enough dose that these residues will kill plants. This is what may happen if too much compost with a high level of chemical residue is applied to plants.
About NPK in compost
NPK stands for nitrates(N), phosphates(P) and potash(K). Some people are talking about compost having all of these ingredients. All three are of use to plants but one of them is usually missing from compost that has been fully formed.
Because of the composting process that involves decomposition, the nitrate factor is released into the atmosphere. This happens all the time when any organic material rots. This is why the atmosphere is approximately 80% nitrogen.
Standard compost that’s been generated by basic decomposition will have a high level of phosphates and potash. Both of these are needed by plants but neither should be added to excess. If plants are provided with too much compost containing an excess of phosphates or potash, then, this may have an adverse effect.
Compost that’s been through heavy worm treatment is a very different material compared to standard compost. When we talk about worm compost, what we are referring to is worm casts. This is compost that’s been ingested by worms and released as casts.
Worms in compost help with the composting process but if they are allowed to stay in the compost for too long, they will digest every part of the compost.
When an entire volume of compost has gone through worms just once, they will start to ingest it again. They will do this because, having ingested compost once and extracted what they can from it, there is still a nutrient value in the digested compost.
Worms will ingest the digested compost for a second and possibly a third time to extract what they can. The problem with this is that the compost that we want to use as an organic feed for plants, will have changed into something quite different.
In extreme cases worms will digest a compost pile multiple times until there is nothing left for them. They will then leave the scene. When this happens, what was once a fibrous compost material, will be a black, dense and heavy material. It will be difficult to identify this as compost as most people would know it.
The question is: will this totally refined form of compost be any good for plants? The answer to this is, generally, no.
There will be a range of compounds that plants can make use of in compost that’s received intensive worm treatment but there is a problem.
Too much compost from worms can affect plants
Compost that’s been fully digested by worms tends to be salty. Salt and plants don’t go together.
This may be the reason why you and others are asking the question: can too much compost kill plants. If you place a large amount of compost that’s been fully reduced to worm casts, the answer would be yes, this would kill plants.
Worm casts derived from compost will still have elements within it that would be useful to plants. Worm-cast compost can be used on plants but you need to apply small amounts. Plants can cope with fluctuations when it comes to variations of nutrients.
In a natural situation, as you would find on the forest floor, organic material will rot down in small diluted quantities. The worms will digest this material and convert it to worm casts. The concentration of worm casts won’t be enough to challenge plants in the wild.
Compare the forest floor situation with the concentrations that can be produced from a compost bin and all that can be generated from organic waste produced from a kitchen.
When we consider the potential adverse impact of concentrated worm casts on plants, there could be an argument for extracting worms from any composting process. This doesn’t need to be a concern.
When you see worms in compost, it doesn’t necessarily mean that the entire amount of compost in the compost bin, will all become worm casts. It will depend on how long you allow the worms to work on the compost that you have.
Don’t leave compost to the worms for too long
If you leave worms to have it all to themselves for long enough, they will convert all the contents of a compost bin into worm casts. Plants will make use of worm casts but you must use small quantities.
When we make compost from kitchen or garden waste, we, generally, eagerly await the compost that’s to be generated. We have a garden full of plants that can make use of standard compost that’s ready to use from about 6 months to a year.
Worms in compost that’s less than a year old won’t have converted it all to worm casts. Standard compost that’s been formed within a year or two can be used on plants without fear of doing any harm.
You will find out what worms can really do if you set up a worm-farm, take look at ‘How to get the most from a worm farm’ to see some does and don’ts about managing worms.
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