Watering compost – the lowdown on compost moisture levels!

  • Date: May 14, 2022

Composting is not a simple as it sounds. Unfortunately, you can’t just throw some waste in a pile and hope for the best. Moisture is one of the most important parts of a healthy, well-functioning compost pile. Depending on your pile, watering compost may be a key part of your maintenance routine. If your pile does not have sufficient moisture, or too much, you can run into a lot of problems. From an ant infestation to a big smelly, soggy pile – neither of which are ideal. Luckily by conducting a simple squeeze test and knowing some of the main signs of a pile that is too dry or too wet, you should have a more successful composting experience!

Why compost needs water

To understand why water is needed in composting it is important to know a bit about how the process works. During composting microbes break down organic material (in the form of anything from food scraps to cotton) to form a nutrient-rich humus or compost. For the microbes to function optimally they need to have certain conditions. A bit like us really. One of their requirements is water – without which they will not carry out their important role in the process.

How much water does compost need?

Keeping the right moisture balance in your compost is key to a healthy compost pile. There is no set amount of water that compost needs. It is not an exact science. For example, the contents of the pile will have an impact, as will the climate. There are no two identical compost piles the world over – so recommending a set amount of water to add would be impossible.

According to the experts, your compost should have a 40-60% moisture content by weight. But what does this look/feel like in practical terms? Compost which is sufficiently hydrated compost should have a wrung-out sponge feel to it. When you give it a squeeze a few drops should escape, water should not ooze out of it.    

Compost too wet?

Compost that is too wet – oozing water out on squeezing – can cause a whole host of issues. Excess moisture will fill the air pockets within the pile, leaving the microorganisms with little or no oxygen to do their job. This anaerobic (no oxygen) environment will result in a pretty foul-smelling pile. Nutrients will also escape with the excess water.

What should you do to fix a soggy compost pile?

Don’t worry – soggy compost can be saved! The excess moisture may have occurred because you have been adding a large amount of watery ‘green’ ingredients such as food scraps. By adding carbon-rich ‘brown’ compost ingredients such as dry leaves, sawdust or even shredded paper this will provide a better nitrogen-carbon balance in the mixture. These materials will help soak up some moisture in the meantime – but to prevent future issues you may need to look at how well you are balancing the green and brown composting materials.

The heaviness of the water-rich ingredients will have made the pile more compact and reduced the amount of air pockets. Give the pile a good mix to incorporate more air. Adequate drainage is also important – so make sure this is place. It may mean drilling some holes in the sides, it all depends on your current set up. Also, does your compost bin have a lid? If not, rainwater may be adding to moisture issue and may need rectified.

Compost too dry?

If your compost is too dry, the microorganisms will simply not have enough water to function. They will become dormant or die. The materials in the pile will not decompose – which makes sense, the microbes don’t have the conditions to work. As well as the lack of breakdown, you may also experience an ant infestation.

What should you do to with dry compost pile?

Firstly, having a dry compost pile may indicate that your brown to green ratio is not quite right. You should have a think about how you can add more water-rich items to prevent this issue cropping up again.

When adding water to your compost pile, ensure that you don’t go wild to begin with. It is difficult to get the amount absolutely spot on but if you add waaay too much, you’ll just end up with a soggy mess! Not what we are looking for. Depending on your pile, a watering can may suffice or hose may be more efficient.

Whatever you use, ensure that your pile is watered equally. This may be more difficult if you have a larger pile. If so, simply water from the bottom up – you may have to scrape off the upper layers to get at the bottom. A bit more physical work involved but definitely worth it.  

Although not the most conventional method, but gaining popularity, you can also add urine to the compost pile to keep moisture levels optimal. The main component of urine is water, but it also has a significant amount of nitrogen. This nitrogen boost can speed up the composting process (it acts a compost accelerator) as well as providing an even more nutrient-rich product. Keeping your water footprint to a minimum and saving money on compost accelerator – wins all round!

The bottom line

Watering compost is a key part of ensuring your compost materials are breaking down in an optimal environment. But like everything in the composting world, it is not an exact science.  No two compost piles are identical in terms of contents and climate so trial and error will be required. By testing a sample of your compost with the squeeze test and being aware of the signs of a dry/wet pile you will be on the right track. Good luck!