What is Well-Draining Soil? - Ep. 153

Karin Velez [00:00:40]:
There are a lot of sayings and advice and instructions in gardening that get repeated over and over again. And a lot of the time, we just kinda nod our head and say, Oh, yeah. Okay. Well, that makes sense. You know, things like the garden needs 1 inch of water per week, or this plant likes full sun, and we sort of instantly know what that means. Mulch is magical and compost is king. Okay. Well, maybe I'm the only one who says those last 2, but think about the description on just about every seed packet, or plant tag? It usually says something along the lines of this plant likes fertile, well draining soil with lots of organic matter. Okay.

Karin Velez [00:01:18]:
Well, the fertility part, we likely understand, and we talk about soil organic matter all the time around here. But what about well draining soil? What does that mean? How do we know if we have it, and what do we do if we don't? If our soil isn't well draining, are we destined to only garden in planters where we can completely control Will The Soil? Can we create well draining soil in our containers, or can we modify our existing soil to make it well draining? We know the soil that we're gardening in is one of the biggest building blocks for a healthy plant and therefore a healthy harvest. What are the possible consequences for not having well draining soil? How does it affect the plants? We're getting into all of that today, including Step by step, how to test any soil in any location to see exactly how well it drains. Let's dig in.

Karin Velez [00:06:49]:
Alright. What is well draining soil? What is the actual definition? Which soils are naturally better draining, and which ones might need a little help? The volume of our soil that is not occupied by soil particles is called the soil pore space? This pore space is critical to allowing air and water and microbes to move in and around the plant roots? Well draining soil is soil that allows water to drain through those pores easily and without outpouring on the soil surface, but not so quickly that the plants and the microbes don't have adequate access to it? A well drained soil has enough space between its particles to allow the water and the oxygen to flow freely, but that doesn't drain too quickly or Do slowly and cause problems for the plants. The soil structure and size and the type of the soil particles Plus, its positioning in the garden are can what can affect the drainage rate. Now if your garden is in a low spot in your yard, It may have nowhere for excess water to go.

Karin Velez [00:08:21]:
Some areas of your garden may just stay saturated from runoff from your roof or other impervious surfaces like the road or your driveway? You might have a naturally high water table that keeps that spot saturated long after everything else has dried up? These are instances where diverting water flow is all that's really needed to help the water drain more freely. But if the soil is compressed or compacted, that means there's not enough pore space. Soil can be compressed by use of heavy machinery or just Too much traffic over the soil. This means not only will there be very little space for water to move through, it means the air and the microbes can't get through either, Which also means you're fine plant roots can't grow through. And if the garden has been tilled over and over again And a hard pan has developed at about the 12 to 24 inch level where the tiller consistently hits year after year, then there won't be any place for the water to drain once it hits that Point. And it can sit there for an extended period of time. This is a different type of impact on the soil structure and a variation on soil compression. But it's not just compressed or compacted soil that can lack pore space.

Karin Velez [00:09:37]:
The structure of the soil, meaning what percentage of each soil component that clay, silt, or sand your soil contains is also a factor. Soils that are predominantly clay or silt can hold on to the water for way too long because of their finer texture and smaller particles, and this Cause the plant roots to literally drown. This is why plants that are native to regions with very heavy soils Often have very deep tap roots to break through that soil and create their own pore space. The other side of this is sandy soil that drains too quickly? If there's too much pore space, not only will the water not hang around long enough to be delivered to the plant roots, It also means the microbes don't have enough moisture to be able to move throughout the soil and help deliver the nutrients to our plants. This is why plants that are native to very sandy regions are those that either have very vast and robust root systems to be able to seek out that water Or those that can easily survive a drought. But in most cases, we're not just planting vegetables that are native to our area. Many of the most Common vegetables we grow came from, like, Mediterranean areas that have beautifully fertile, loamy soil. And there are very few of us that at garden in areas that have those naturally beautiful soils for gardening? So knowing our native soil structure can be a Start in understanding how well draining our soil is.

Karin Velez [00:11:06]:
If you know you have heavy clay soils, you know that soil is likely to remain saturated for longer than if you have a very sandy soil? Now this can be a good thing if you know how to manage it. It's how we manage to go So long between rainstorms here without completely losing our crops. Heavy layers of mulch help to slow the rain flow into the soil so it doesn't become Oversaturated as quickly, and then that same mulch helps the soil at the surface retain the moisture while the naturally dense clay hangs onto it beneath the soil surface. But it also means there are a lot of crops that just don't do well in that heavy soil, which is why we constantly amend with organic matter. Now the same thing applies if you have sandy soil. You're not likely to face a problem where too much rain causes your garden to become waterlogged, But you will likely find that frequent waterings are necessary because the little bit of water that is retained in that soil It's very quickly used up by the plants and the microorganisms. Amending with organic matter is the solution here too. Compost, shredded leaves, aged manure, leaf mold, these are all perfect for improving the soil structure and increasing the water retention.

Karin Velez [00:12:22]:
And, of course, adding mulch will slow down the absorption of the water as it's hitting the soil surface, further improving the retention. Now if your soil is compacted or if you've got a bit of hard pan beneath the surface, You might wanna look at creating raised beds. This doesn't necessarily mean you need to resort to actual planters. You can create a raised bed without having a wooden or metal structure to it? We've done this in 1 particularly rocky and heavy clay field by just layering compost and other organic material onto the surface of the soil? We're not tilling it in or turning it under in any way. We simply start with several inches of compost at the end of the season, Let it winter over, then add additional organic matter in the spring before planting directly into it. The compost that is in contact with the Soil over the winter gets inoculated with the active microbes in the soil. The soil microbes move some of the organic matter into that top layer of the soil, improving it, And the plants are mainly grown in the top 4 to 6 inches anyway, so the organic matter is holding the water where the play the main plant roots are. As each Season goes on, we add more organic matter each season, and we have ourselves a nice raised bed of soil that's about 6 inches above The native soil surface at any given time, and it isn't negatively impacted by the hard soil beneath.

Karin Velez [00:13:48]:
Now, of course, you can do this with raised planters. I will link to the episode where I talked about how to fill a raised planter or container. But, essentially, if you layer your materials in there and have the proper components, You'll naturally be creating a well draining soil. After a while, even if you've amended your beds or created your own soil, things can change. Weather events, the types of plants being grown, our actions as gardeners within the beds can all change how our soil drains. And sometimes as new gardeners or when we're gardening in a new area, we don't really have any idea of what type of soil we're working with. I'll link to the episode about soil structure and how to test your soil so you understand what the components of your soil are and what that can mean for your garden. But aside from that, there is a super easy test that you can conduct, whether it's in your native soil, an amended bed, or in a container that will tell you exactly how fast or slow your soil is draining so you can have a plan to make adjustments where necessary? We'll go through that step by step right after this.

Karin Velez [00:15:38]:
So how do we test Our soil drainage, so we have an idea of what we're working with. It's a very simple test. It doesn't take very long at all, and it's very accurate.. You're going to need a shovel, a ruler, and a bucket of water or access to your garden hose or some other running water. 1st, dig a hole in your gardening space that's roughly 12 inches square and 12 inches deep. If you're on metric, that's about 30 centimeters. And, yes, you can do this with your raised container soil too? This is especially helpful if you've had your containers for a long time and haven't amended a whole lot over that time or if you find the success Dust of your gardening in those containers has changed for the worse recently. Once you've got your hole dug, fill the hole with Water, and then let it drain. Once that initial water has drained out, fill the hole again, and this time, stick a We're in there to measure how deep the water is initially. This should be pretty close to that 12 inches or that 30 centimeters that you dug out initially. Right? After 15 minutes.

Karin Velez [00:16:47]:
Use your ruler to check the depth again to see how much the water level has dropped. Multiply that difference by 4? And this will tell you how fast your garden area will drain in 1 hour. If your soil is draining water at a rate of 1 to 6 inches per hour or 12 and a half to 15 centimeters, That means your soil is well drained. Perfect. If, however, the water is draining less Then 1 inch or 12 and a half centimeters per hour, then it's draining too slowly. And if it drains faster than six Finches or 15 centimeters in an hour, it's draining too quickly. Now I have a few raised planters, some of my planter box direct planters that are out front that I filled at the end of the year last year, and then there's a matching set that I didn't fill until this spring. I can tell you the soil seems to be settling Differently in each of those sets of containers.

Karin Velez [00:17:48]:
The mixture of components I put in the one seems to be sitting just more tightly than in the other. But before I go and do anything to that soil, I'm gonna do this test to see if it's even affecting the drainage or the soil pores at all. It might seem tight, But I've gotten great yields of carrots out of there in the past week or so, so there may not really be anything I need to do. My perception of what is going on may not mean anything to the plants. So I'll do this test, and I'll likely do a soil test too to check the pH and the fertility in each of those sets of beds just to see what the differences are there, and I won't make any decisions until I've done those tests. The drainage test will also help me identify which beds might need to be watered longer than others when we do have to water And which ones can get by with a shorter time with the hose? Now hopefully, this has answered the question of what Well draining soil is, how we can figure out if we have it, and how to correct it if we don't. If you're on my email list, You'll have these step by step instructions in your inbox this coming Friday in the weekly newsletter. If you're not on the email list, Head to just grow something podcast.com to sign up, and you'll get these details at the end of the week.