Soil is the foundation of your garden. Just like a building needs a good foundation, a garden does, too. When you provide your plants with the right foundation, it is noticeable in the plants’ health, productivity, and longevity. The ground you’ll be considering for planting may not be in the most ideal condition or have the proper characteristics for what you want to plant. You’ll need to condition that environment for your plants to flourish. That’s where amendments come in. Amendments are incredibly important, and here at Nourse Farms, we talk about them often. Let’s review soil and other important terms before we “dig in” to soil amendments.
Is there a difference between soil and dirt?
One of our employees explained this difference well: “When I first started in agriculture, a farmer I worked with explained the difference between soil and dirt to me like this: ‘Soil is what makes it possible to grow our plants; dirt is what you get on your clothes and under your nails.’”
Another employee added a nugget of wisdom gleaned from Tim Nourse himself: “I was told, ‘Plants grow in soil. Dirt is what you sweep off your kitchen floor.’”
These are two memorable ways of explaining that soil supports life; dirt does not.
What is soil?
Soil is a mixture of broken-down rock particles of varied sizes, minerals, organic matter, gases, liquids, and organisms. Soil serves as a medium for plant growth, which is why we talk about it so much. Healthy soil lives! There should be lots of organisms that live and die in soil, some large enough for you to see with the naked eye and some that you need a microscope to see—bacteria, insects, fungi, and more. All contribute to, along with air and water, the health of the soil, the plants growing there, and the earth overall.
Organic matter is an important soil component. It is made up of living organisms and dead organisms in varying states of decay, as well as waste products from living organisms. Organic matter affects water retention, nutrient levels, and more.
Soil serves a greater purpose than holding a plant in one place. Different plant types will only survive or thrive in specific soil conditions. For example, blueberry plants require intermittent water and a rather acidic soil compared to many other fruits and vegetables. Some varieties of plants thrive in varied soil conditions, such as Millennium asparagus. One customer described it as being so vigorous in his rich riverbed soil, he tried growing it in the sand of Cape Cod and was shocked to have succeeded (with our soil amendment advice, of course)!
What kinds of soil are there?
A soil texture or type refers to the overall range of particle size and shape that makes up the soil where your plants will lay roots. There are many types of soil, as most soils are made up of a combination of particle sizes. Particle size and shape make the soil feel different to the touch, and affect how water, air/gasses, nutrients, and even plant roots move through it. If the soil is comprised of a very high percentage of the smallest particles, it is clay soil. Silt particles are a bit larger than clay, and sand particles are larger still. Larger particles leave larger gaps between each other for movement of air, water, and more. The most common soil types or categories are: clay, silt, loam, sand, clay-loam, sandy-loam, chalky, and peat.
Soil with more clay-sized particles holds water, minerals, and nutrients more readily. This soil type feels slick and somewhat sticky and is slower to warm in spring than other soil types. Particles snug together more tightly, making the soil heavy or dense. This type of soil is very easily compacted, so you should try not to walk on it in planting areas—keep to pavers and pathways to help those roots below from becoming compressed. Clay soil hardens when dry. It may be a bonus in raised beds, as they dry out quicker than conventional beds and if you are working with clay or clayish soil, building raised beds can be a smart alternative to planting in the ground, as they can give your plants the improved drainage they need to survive.
Silt particles are larger than clay, but much finer than sand. Silt can feel soft and smooth, even silky or powdery like flour. It can hold nutrients and water better than sand. It is very light and can easily blow away in the wind or wash away quickly with flowing water if there is no vegetation to hold it or slow its movement. It can compact easily like clay and stay too wet for too long for many plants.
Loam, or loamy soil, is medium-textured, loose, and crumbly when dry, and has a great balance of qualities for growing many, if not most, crops. It typically contains 40—50% each sand and silt, with 10—20% clay. The ratio of particle sizes allows it to hold nutrients and minerals well, makes it easy to work with, and also gives it the ability to hold water long enough to give roots time to absorb water, yet drain quickly enough to allow plant roots to breathe adequately.
Sand feels rough or gritty and erodes easily. Particles are large compared to silt and clay, allowing sizeable gaps between for air, water, nutrients, and organisms to move easily. In the spring, sand or sandy soil warms earlier than other soil types. You will need to water this type of soil more frequently compared to other soil types.
This is a loamy soil that includes a much higher percentage of clay-sized particles. This soil type will require less frequent watering than loamy soil or sandy-loam so that roots don’t stay too wet.
Loamy soil with a much greater proportion of sand-sized particles. You will need to water this type of soil more frequently than clay or silty soils but less than sandy soils.
Chalky soil is typically made up of larger grains so will drain well but can be clumpy when wet. It is usually strongly alkaline, so, if the area is deep, it is an ideal location for asparagus which thrives in a ‘sweet soil.’ It is not a good place to try to grow blueberries, which require a much more acidic soil.
Peat or Peaty Soil
Peat or peaty soil is not very soil-like because it is predominantly organic matter instead of having a rock origin. It is very unlikely that you have peaty soil in your garden. Peat is very slowly formed by layer upon layer of wetland plants (like sedges and mosses) growing, dying, and decomposing. It will feel spongy, especially when wet, and can stay saturated for a very long time, which is not healthy for most fruit and vegetable crops or flower gardens.
Peat in your garden
Peat is common component for potting mixes and a good amendment for raised beds and garden soils. Contrary to what you might think, it does not stay super-saturated if mixed with soil in the right amounts. Avoid using a high percentage of peat to avoid excess soil moisture. When first adding peat be sure to moisten it in a wheelbarrow or other container before mixing into your soil as it can be difficult to re-hydrate. Peat is quite acidic and can be a good amendment for blueberry beds however its acidity is lost quickly and therefore it is not a reliable method of soil acidification.
We’ve mentioned alkaline and acidity and we know that that often requires a little explanation.
What is soil pH?
Soil pH refers to the measurement of the acidity or alkalinity. Soil pH is an important variable when talking about plants because it impacts chemical processes, which includes nutrient availability for plants. The pH scale is 0 to 14, with a pH of 7 being considered neutral. If pH is higher than 7, it is considered alkaline and if pH is lower than 7, it is considered acidic. A small decrease on the pH scale represents a very large increase in acidity. Most plants thrive in soil with a pH between about 6 and 7. To a strawberry plant, 6.5 pH would be perfect, but a pH of 5 would be too acidic. If you want to learn more about soil pH, we recommend giving the USDA Natural Resources Conservation Service website a visit.
The ideal pH for plants you can get from Nourse Farms:
- Strawberries: 6.5—6.8
- Raspberries: 6.5—6.8
- Blackberries: 6.5—6.8
- Blueberries: 4.5—4.8
- Currants: 6.0—6.5
- Gooseberries: 6.0—6.5
- Elderberries: 6.0—6.8
- Asparagus: 7.2+
- Horseradish: 6.2—6.7
- Rhubarb: 6.0—6
Why does pH matter?
Soil pH directly impacts the nutrients available in the soil, as well as other factors that impact plant growth, such as soil bacteria and structure.
How do I figure out my soil’s pH?
Test it regularly! You can quickly and easily test your soil’s pH using a Digital Soil pH Meter. The tool comes with easy-to-follow instructions that making testing as straightforward as possible.
We strongly recommend against guessing or assuming the soil pH. Test the soil and try to apply the proper amount of lime or sulfur and mix it several inches into the soil where the roots will be growing. If you need to make an adjustment later, and apply the material at the soil surface, it will take longer to affect the plants.
Once you know your soil’s pH, it’s time to make any necessary amendments! Here are some ways you might need to amend your soil.
- If you need to raise your soil pH, you can add lime, which will reduce its acidity. Some would say to make it more alkaline or sweet.
- If you need to lower your soil pH, you can add sulfur, which will make it more acidic or sour.
Soil pH changes are carried out by soil microbes and take place only while soils are warm. It can take 3—4 months of active growing season for the soil’s pH to fully adjust after the amendment is mixed in. Therefore, it is best to amend the soil prior to planting (even a year in advance), so that the soil is conditioned deeply and broadly where the roots will be growing over the next few years.
Our Planting and Success Guide includes a lot of helpful information, including a chart on page 19, that we strongly encourage you to review.
Soil amendments aren’t just to adjust the pH!
Take, for example, blueberry plants. We often recommend using a combination of woodchips to increase aeration, drainage, and weed suppression and sulfur to get the soil to the acidity blueberries thrive in. However, while woodchips can be helpful for blueberries, they could kill raspberry and other bramble plants. Amendments are very plant specific.
Some other examples of soil amendments include:
- If you need to improve your soil’s aeration, adding woodchips or perlite will help it drain more efficiently.
- Gypsum can be added to a clay soil to improve aeration and drainage as well as reducing erosion.
- If you need to improve your soil’s aeration and moisture retention, you can add vermiculite, though it adds less aeration than perlite.
- You can improve the water-holding capacity of sandy soil or sandy-loam by adding organic matter.
- You can also increase water drainage capability of a clay-loam by mixing in lots of organic matter.
What to avoid
We strongly recommend against adding sand to clay soil for growing plants. Clay soil can be black or red, is as fine as dust, and is hard for plants to move through. Clay soil is waterlogged in wet months and rock hard in summer. Adding sand will create a cement-like mixture that will not be better for water holding or drainage and it will make it more difficult for your plant’s roots to grow.
If your soil is clay or clayish, the best thing to do is build raised beds to give your plants the greatest possible opportunity for soil drainage, even if you only get occasional wet periods.
Avoid creating a clay bowl by digging out the native soil and replacing it with a better-draining mixture because water will get impeded by the clay sides and bottom and not drain away from the roots. This can cause a host of problems such as root rot and lead to a soil that does not allow oxygen to permeate, which will prevent roots from being able to breathe. Over time, deeper roots will rot and new roots will form in the top few inches of soil, which makes plants weaker and less likely to survive difficult conditions.
Mushroom compost is becoming increasingly more available however we do not recommend using it as a soil amendment as it often contains high levels of soluble salts and can burn plants.
We’re here to help!
Nourse Farms talks about soil amendments frequently because we want you and your plants to be successful! Providing your plants with the healthiest environment you are able to will encourage great growth and yield and even help with pest and disease issues.