How to improve soil for gardening

You should always strive to use the best possible garden soil in your vegetable garden. But even so, the most important one thing you can do is to continuously improve the quality of your soil.

And the good news is that there is one thing that always works, adding organic matter.

A fertile soil needs to be rich in organic matter for plants and vegetables to grow and thrive. And the worse the quality of your soil, the more organic matter you should add.

So what is organic matter?

From an organic gardening perspective, organic matter is simply put all that was once alive and that has now fallen to the ground. This does in other words not include a organic fertilizer. Examples from your garden may include leaves, pine needles, twigs, branches, bark, flowers, fruits and berries.

When they fall to the ground and rot, or decompose, the decomposing organic matter provides food to innumerable soil organisms including worms and soil bacteria that work together to enrich and aerate your soil.

At the end of the decomposition process the organic matter turns into what we call humus, which simply put is the organic component of soil. 

Humus is a dark, slightly oily substance that helps bind the soil as worms and bacteria work it into the soil. Humus also increases the soil’s capacity for holding moisture and provides the plants and vegetables with much needed nutrients, nitrogen being the most important.

Improving soil is a continuous process

For a healthy soil, it is important to understand that it is not enough to add organic matter once.  Your existing soil needs to be improved at least once a year to remain a good soil that that yields healthy harvests.

There are several reasons why organic matter needs to be added more than once:

  1. Organic matter shrinks in volume as it decomposes
  2. Vegetables and plants depletes the soils reserves of nutrients
  3. Nutrients are over time depleted by rain

Adding organic soil amendments will over time improve soil quality. It is, however, a process and for several different reasons organic matter needs to be added more than once for a soil to remain healthy and fertile. Next we will look at how to improve different types of problem soil.

How to improve problem soils

There are several different types of problem or poor soil that gardeners may face. And each type of problem poor soil has its own needs and wants.

Here in this article we will look at how you can improve sandy soils, clay soils, rocky soils, hard soils and over fertilized soils.  

How to improve sandy soil

Sandy soil is typically found in areas with high winds, such as coastal areas. Here are two easy ways to improve the quality of your sandy soil and turn it into a moist, crumbly and fertile soil.

1. Add organic matter to the soil

Compost and aged green manure are two examples of organic matters that will help improve the structure of the soil, as well as add nutrients and attract beneficial soil organisms.. 

You can either add it in bulk, or mix it in with the top layer of soil before planting. Adding organic compost, grass clippings or straw will help with water retention and nutrient content of the soil, which will make it easier for plants to take root and grow. 

2. Add mulch

Mulch helps to retain soil moisture, as well as providing some nutrients. It also helps to suppress weed growth giving your plants less competition for nutrients and water. 

As the mulch decomposes your soil will benefit from the added nutrients that help create a healthy environment for beneficial soil organisms. Examples of mulch include compost, straw but also grass clippings and wood chips.

How to improve clay soils

Using soil amendments to improve soil fertility
Healthy soil with good texture and using Perlite

Clay soil is notorious for being difficult to work with because it doesn’t drain well and has a tendency to be less fertile. 

The dense structure of clay soils make it hard for plants to develop a healthy root system as there is not enough available oxygen and water. So how do we enhance the quality of heavy clay soil?

The number one rule when working with clay soils is not to dig deeper than you need. Start by focusing on improving the area needed by your plants. Dig no deeper than 18 inches and focus your attention on increasing access to more air.

1. Add organic matter to the soil.

This will help to loosen the heavy clay soil and make it more receptive to water and nutrients. Compost, composted manure and leaf mold are all good alternatives. 

2. Aerate the soil.

This will help to improve drainage and air circulation, which is essential for healthy plant growth. Adding mulch will help aerate your soil over time but for faster relief you should consider mixing in organic amendments in your soil.

3. Use raised garden beds or containers.

Planting in raised garden beds or containers makes it easier to keep the soil loose and aerated, which is especially important for clay rich soils. Whether you are using permanent garden beds or raised garden level beds it is easier to improve the garden soil quality when you work with a confined space.

4. Mulch the soil.

Mulching helps to retain moisture in the soil and prevents the formation of hard crusts. And as the mulch decomposes, organic matter is added to your soil overtime.

Do not add sand as you may end up with a concrete-like soil structure. Instead use organic matter like compost, peat moss and leaf mold to loosen the structure of the soil. 

We use Perlite to help aerate potting soil when it gets too dense over time. But this gets costly for larger areas. Gypsum is hailed by some as a clay soil buster but from the reports I have read experts are still divided on whether the effects have been universally proven. 

How to improve rocky soils

There are many ways to improve rocky soil in your vegetable gardens, depending on the severity of the issue.  In some cases, you may just need to add organic matter to the soil to help improve its structure and drainage. In other cases, you may need to break up the rocks using a tool like a pickaxe or jackhammer.

Good soils are the foundation of a healthy garden. In order to have good soil, you need three things: organic matter, water and air. And if your garden has very rocky soil, it’s important to improve the garden soil before planting anything.

  1. Start by trying to get rid of as many of the larger rocks as you can. 
  2. Improve your rocky soils by adding compost or other organic materials that will provide nutrients for plants as well as help keep moisture in the soil. 
  3. If you don’t have any compost on hand, try mixing grass clippings with some topsoil from your yard. Peat moss and leaf mold are also good alternatives.

Herbs, vegetables and other plants will not grow well in rocky soil, and they may eventually die if they’re forced to grow in such conditions.

How to improve hard soils

Soil can get dense and compact over time. And if you notice puddles forming on the soil surface after rain you know your soil is too hard and dense. 

1. The first thing you’ll want to do is assess the condition of your hard soil by digging down into it with a shovel or trowel. 

If the soil is very compacted then start by adding plenty of organic material like compost, well-rotted horse manure, straw or leaf mold which will help loosen soil over time as these organic materials decompose. 

2. If your soil is very hard you can also add some coarse sand. This will help improve the drainage of your soil and make it less dense.

3. Finally, you can use a soil improver such as Gypsum. This will help break up the clay in your soil and improve its drainage

How to improve over fertilized soils

Over-fertilized soils can be a common issue for well meaning gardeners. 

It is always good to remember that your plants, herbs and vegetables will tell you if they need a boost. Thriving plants do not need or benefit from adding more fertilizers. 

If your soil is too rich in nutrients, it can cause problems such as overly lush growth, nutrient deficiencies, and even toxicity. Thankfully, there is a way to correct over-fertilization and create healthy soil for your plants.

1. You can amend the soil with organic matter.

Adding compost or other soil amendments like aged horse manure will help improve the structure of the soil and create a more balanced environment for plant growth.

Also, you will be pleased to know that mother nature will over time help you balance the level of fertilizers in your soil. This is however not a quick fix but I believe it is important for all gardeners to understand the process.

2. Mother nature will over time dilute the level of fertilizer in your soil.

When you water, your soil can only hold or bind so much moisture. When the soil is saturated with moisture any additional water will run through to the deeper layers or even bedrock. This phenomenon is referred to as Leaching

And when excess water runs through your soil some minerals and fertilizers are also lost. This process will over time help balance and correct high levels of fertilizers in a completely natural way.  

Bonus: Cover crops convert organic matter to goodness

Cover crops are simply put crops that are planted to cover your garden beds rather than to be harvested. Benefits of cover crops include protecting against soil erosion, weeds, pests, diseases as well as improving your soil as they decompose.

Cover crops can be planted between rows of other plants or for example on raised beds put to rest over winter.

How to test the structure of your garden soil

Soil is the foundation for any garden. It’s important to have a good understanding of how your soil is structured so you can know what it needs and how to properly fertilize or amend it. 

You can send a soil sample to be professionally tested but as a home gardener you are most likely looking for knowledge on how to test your soil texture yourself. Knowing if your soil has a clay, sand, or loam structure will help you understand what type of nutrients are needed in order for your plants to thrive.

One way to test for loose soil or compact soil is to take a sample and drop it into a glass of water. If the soil floats, it is not good for planting. If the soil sinks, it is good for planting. 

Another way to test the soil is to grab a handful and squeeze it into a ball. If the ball falls apart when you let go, the soil is too sandy. If the ball stays together but crumbles on touch, the soil is good for planting.

You can also test how wet or dry your soil is by feeling with your fingers. Dry soil feels gritty, while wet soil feels muddy. Soil that is the perfect moisture level feels like a squeezed sponge.

Use a soil test to assess the quality of your soil

If you’re a gardener, then you know the importance of soil quality.If your soil quality is poor, then your plants will struggle to grow and thrive. 

Luckily, you can buy a home soil test kit to test the quality of your soil. There are several different methods for testing your soil. So whether you’re a beginner or an experienced gardener, you’ll be able to accurately assess the quality of your soil. 

One common way to test soil quality is by using a pH test kit to measure soil pH. You can buy pH test kits at most local garden centers or at online retailers. 

This test help measure whether you have acidic soil, alkaline soil or neutral soil. A pH level of 6.5 – 7 is slightly acidic to neutral and is ideal for most herbs and vegetables. But you may need to adjust the soil pH level depending on the type of plant you are growing.

Read the seed package or plant label for the requirements of your plants. 

I invite you to read about my mother’s home pH level testing method. And no, I am not claiming she invented the method. But she did tell me about it a long time ago.

Another way to test your soil’s quality is by using a soil test kit. Soil test kits measure things like the amount of nitrogen and phosphorus in your soil.

Soil test kits are especially important if you are planning to grow a specific type of plant, as you will need to make sure the soil has the right nutrients for that plant. You can buy soil test kits at most garden stores, or online.

How to improve soil quality for successful gardening
Replanting coriander (cilantro) taking great care of delicate roots as soil needs a boost
Helpful resources: 

Michigan State University, MSU Extension

University of Maryland Extension

Meet the author: Mattias is an experienced gardener spending most of his free time on his knees among herbs, plants and garden vegetables. For the past two years he has been sharing gardening projects and how-to tutorials on the NordicLavender website and YouTube channel.