Why Does My Soil Dry Out So Fast After Watering?
Updated: Oct 18
If you water your pots, raised beds or garden and the soil seems dry again almost immediately, the obvious response is to add more water.
So you water again.
And again.
Before long, you’re spending half the summer chasing dry soil with a hose. I'm sure most of us have been there at some point, I know I have before I knew all about soil biology.
But sometimes the problem isn’t about how much water you’re putting on, it’s about what happens to that water once it hits the soil.
I'm sure you've seen water running down cracks, around the outside of a pot, or through a few easy channels and wondered where the hell did it all go.
But before you increase your watering, there’s a much better question to ask:
Is the water actually reaching the roots, and can the soil hold enough of it between waterings?
Do this simple test first
Next time you water, water as you normally would, then wait about 10 minutes and dig down into the soil either with just your fingers or a small trowel.
In a pot, gently check a few centimetres below the surface and towards the centre of the root ball. In a raised bed or garden bed, dig down in a couple of different places.
You’re looking for one of three things.
The soil is evenly moist.
The top is wet but it’s dry underneath.
Or some areas are wet while others are still completely dry.
If you find those dry areas, simply putting more water on faster may not solve the problem.
Why can soil still be dry after watering?
Water follows the easiest path available.
If soil or potting mix has dried out badly, shrunk away from the sides of the container, become compacted, or developed cracks and channels, water can bypass parts of the root zone and head down one of those easier paths.
You see this a lot in older potting mixes, you pour water onto the top, it disappears quickly and comes straight out the bottom. It looks like the pot has had plenty of water.
But break the root ball apart and you can sometimes find large sections inside that are still almost bone dry. Don't do this if you want to keep the plant, just take my word for it.
The same thing can happen in raised beds and garden soil, just on a larger scale.
Soil structure matters
A healthy root zone contains a network of pore spaces of different sizes.
Some allow excess water to drain and air to move through the soil. Smaller pores hold onto water and make it available to plants between watering.
This kind of 'sponge-like' structure comes from a combination of things.
Soil particles, organic matter, roots and biological activity all play a part.
Fungal hyphae can help bind soil particles together, bacteria produces sticky substances that contribute to aggregation - the binding of smaller particles into larger, stable clumps called aggregates.
Plant roots physically move through soil and release compounds such as simple sugars and carbohydrates that feed organisms living around them.
Over time, all of this helps create the crumb-like structure we associate with functioning soil.
But biology isn’t working alone.
A very sandy soil will still naturally drain faster than a clay soil, compacted soil can restrict infiltration regardless of how much organic matter is present and old potting mix can behave very differently from garden soil.
That’s why I don’t think it’s useful to describe every dry-soil problem simply as a biology problem. It’s a soil-system problem. Although, when biology has been removed or depleted from soil it leads to issues with chemistry and structure.
What about soil that repels water?
Sometimes water doesn’t soak in at all.
You've probably also see how water can bead on the surface or sit there before finding one or two places where it eventually disappears.
This is often described as hydrophobic or water-repellent soil.
It’s particularly common in potting mixes and soils that have become extremely dry.
Organic materials can develop water-repellent coatings as they dry, and once that happens it can take time to properly re-wet the material. Incidentally, the same coatings are responsible for attracting water.
That's why more water applied quickly isn’t necessarily the answer.
So how do you fix dry soil?
Start by getting the soil properly wet again.
If you’ve found dry pockets, apply water slowly rather than dumping a large amount on at once.
Give it a light watering, wait a few minutes, then water again. Perhaps use a sprayer rather than a watering can or hose.
Two or three slower passes can allow water to move into areas that a single heavy watering simply bypasses.
For a badly dried-out pot, you may need to re-wet the root ball much more slowly. In some cases, soaking the pot for a short period can help the mix take water back up, provided you leave the container to drain properly afterwards.
Once you’ve dealt with the immediate problem, look at why it keeps happening.
Add organic matter where it makes sense
Good compost can improve the soil’s ability to hold water, particularly in sandy or low-organic-matter soils. It also provides food and habitat for soil organisms.
But adding more compost isn’t automatically the answer to every struggling bed.
If you’ve already been adding plenty and the garden still isn’t responding, there may be something else limiting the system.
Keep the soil covered
Mulch reduces evaporation from the soil surface and buffers temperature swings.
That means more of the water you put on stays in the root zone rather than disappearing back into the atmosphere. I even use a woodchip mulch on my potted plants
Watch compaction
If water sits on the surface and struggles to move down, structure may be limiting infiltration.
Compacted soil has fewer useful pore spaces for water, air and roots.
Avoid repeatedly working wet soil and try to keep traffic off growing areas where possible. If it's a pot or raised bed you can gently push something like a chopstick into the pot in several places or a garden fork into your raised bed.
Keep living roots in the soil
Roots are a major part of soil structure.
They create channels, feed organisms around them and leave organic material behind as they grow and die.
Where practical, keeping something growing helps maintain the system underneath. When harvesting has finsihed cut the plant off at the soil surface to keep the roots in place. They will decompose and leave spaces open for moisture.
Look at the biology too
If the physical structure is reasonable, organic matter is present and the soil still behaves poorly, weak soil biology may be part of the picture.
Fungi, bacteria and the rest of the soil food web contribute to aggregation and nutrient cycling around plant roots. That’s where biological amendments can be useful.
Not because biology magically fixes every dry-soil problem, but because it is one part of the system responsible for building and maintaining a functioning root zone.
What I’d do first
If your soil is drying out unusually fast, don’t immediately increase the watering schedule.
Water it normally.
Wait 10 minutes.
Dig down.
If the soil underneath is still dry, you’ve learned something important.
The issue isn’t simply how much water you’re giving the garden, it’s how that root zone is accepting and holding it.
Start by re-wetting it slowly. Then look at organic matter, mulch, compaction, roots and biology to work out which part of the system needs attention.
That’s a much better place to start than spending another summer chasing dry soil with a hose.
Not sure what’s limiting your soil?
If you’re still not sure where the problem is, I’ve put together a simple free soil test you can do at home.
It only takes a couple of minutes and can give you a much better idea of what’s actually happening underneath the surface.
Already adding compost but still not getting results?
If you’ve been adding compost, fertiliser and other inputs and the garden still isn’t really responding, it may be worth looking at the problem from a different angle.
If biology looks like part of the problem
If the biological side of your soil is one of the pieces that needs support, RootWise Balance is designed to support beneficial biology around the root zone.
Interesting article