Soil Preparation: How Do You Prepare Garden Soil for Planting?
Healthy vegetables are dependent on good soil for their growth and harvests. A garden built on well-prepared soil offers a powerful start to the growing season. Our guide to soil preparation will teach you how to identify the type of soil you have, how to improve it, and give your plants the best start they can have!
Planting doesn’t begin with a seed. It begins with the soil. You can’t have healthy, productive plants without rich, soft soil that allows the roots to grow deeply enough to absorb nutrients.
The good news is that you can enhance your soil with organic matter. Rich soil literally has its own life with microorganism activity (such as earthworms) that breaks down matter to release essential nutrients to your plants. Organic matter improves soil’s ability to hold nutrients and moisture while draining well, loosens soil to increase oxygen for plants, and anchors and stabilizes roots.
Spring Soil Prep: 3 Easy Steps
Beginner gardeners should not worry about being overwhelmed – we’ll dive deep into full soil preparation below, but here are three basic steps you’ll want to follow in the spring:
- Clear out rocks and debris. Dig up grass by cutting the sod into small squares and prying it from the planting area with the spade’s end.
- Loosen the soil. The soil needs to be loose enough to allow roots to reach at least 8 inches, or 12 if possible.
- Adding Organic Matter. If all you remember to do this spring is to add organic matter such as compost, that will get you off to a great start! Spread no more than 3 inches of compost or aged manure on your soil and add it on a day when the soil is moist but not wet. The organic matter is often dug into the soil by gardeners.
A no-dig method is also popular because it exposes fewer weed seeds and does not disturb the soil structure; simply leave the compost on the surface and let the worms do the digging for you!
The shape of the soil is what really determines the growth method. If you have poor soil, we would recommend using compost. Or, if you have hard, compact soil, build a raised bed. Or, you could grow in planters and containers.
A couple other tips:
- Warming Your Soil. In colder areas, consider a raised garden bed to help your wet, cold soil dry out more quickly. Before planting, you can cover your garden beds with black plastic to cardboard to block light and protect your plants from snow, rain, and erosion.
- Clearing Out Weeds. Early weed control can be accomplished by lightly disturbing the soil surface before planting, then warming it with sheets of clear plastic. The weed seeds should already be up, so pull them out with your hands or remove them with a hoe. Avoid digging the soil, which will just bring new weed seeds to the surface; the idea is to remove those already established.
The rest of the year, and every year to come, will prove to be much easier for you if you continue to build rich, dark, fertile soil!
Digging Deeper: Know Your Soil
What kind of soil do you have? Is it alkaline or acidic? Is it too thin or too rich in nutrients? We will discuss three important components:
- Soil Type
- Soil pH
- Soil Nutrition
Rocks and organic matter mix together to form soil, allowing plants to survive. Organic matter is made up of both dead things and living plants.
In soil, there are three types of rock particles: small (clay), medium (silt), and large (sand). Different blends of these particles will affect:
- How water drains. Unlike clayey soil, sandier soil doesn’t hold enough water because it drains too slowly. Clays don’t maintain enough water because of their rapid flow.
- How much oxygen plant roots get. Compacted clay takes up very little space.
- How well the soil holds nutrients. With silt and clay, nutrients are held in tiny particles; however, in sand, nutrients are lost too quickly.
- How quickly the soil will erode. Silt particles are lighter than clay and heavier than sand and more prone to erosion.
The clay soil keeps its shape in clay balls. It can bake hard in summer and become flooded in winter. Very fine particles are slow to absorb moisture and drain. Clay soil holds the moisture in and drains slowly.
In the spring, sand warms up rapidly because of its size and ability to drain quickly. Sand does not hold onto nutrients very well.
Smaller particles than sandy soils. The texture has a slightly floury feel that retains moisture and nutritional value longer.
In a perfectly balanced soil there should be equal portions of sand, silt, and clay. This type of soil is called loam. Loamy soil holds moisture while allowing oxygen to reach the roots of plants. It also contains humus, which is organic matter. The soil is fertile, easy to work, and contains a lot of organic matter.
The soil in a good garden will crumble easily, and it will not form a hard ball when squeezed nor crinkle or crust over when dry.
What is the best way to determine the amount of sand, silt, and clay in your soil?
One of the simplest and most generic methods is the feel test: rub a moist piece of soil between your fingers to determine whether it is sand, silt, or clay.
Alternatively, you can also conduct a ribbon test, where you squeeze a wetened soil ball between your thumb and forefinger until it forms a ribbon. Sand or sandy soils won’t ribbon; loam, silt, silty clay loam, or clay loam soil ribbons less than 1 inch; sandy clay loam, silty clay loam, or clay loam ribbons 1 to 2 inches; and sandy clay, silty clay, or clay will ribbon more than 2 inches.
As opposed to particle size, soil pH is all about nutrition and fertility. Soil pH affects plants’ growth by affecting the availability of nutrients and minerals as well as how well the plants are able to access, absorb, and regulate these substances. In soils with an extremely low pH or an extremely high pH, nutrients will be inadequate or toxic, resulting in weakened flowering plants.
It is ideal for garden vegetables to have a pH range between 6.0 and 7.0 because this is when microbial activity is greatest and root development is best. However, most plants tolerate a wider pH range, while some plants have particular pH preferences.
Plants require three primary nutrients: nitrogen (N), phosphorus (P), and potassium (K). On the package of a fertilizer, these values are separated by a dash (N-P-K); the numbers indicate the percentage of each nutrient in the product.
The addition of aged manure to the soil and the application of alfalfa meal, seaweed, fish, or blood meal can increase the amount of nitrogen available to plants. This is primarily to increase the growth of broccoli, cabbage, greens, and lettuce.
Phosphorus (P) promotes root development as well as fruit and seed formation. It is essential for cucumbers, peppers, squash, tomatoes and other plants that develop after the flower has been pollinated. Add bonemeal or rock phosphate to increase phosphorus.
Potassium (K) is essential for root vigor, disease resistance, and flavor. Include greensand, wood ashes, gypsum, or kelp in your soil to increase potassium.
An analysis of the soil can tell you how many nutrients are available. You will most likely receive information on phosphorus, potassium, magnesium, and calcium.
Get a Soil Test
In the spring and fall it is a good idea to send a soil sample off for testing, so you’ll know whether or not you need to add lime or sulfur to adjust the pH.
Most university extension programs offer soil testing so gardeners can learn about their soil type, what nutrients are lacking, and how to improve their soil. You can buy kits from garden stores or order them online. This will require digging up a small amount of soil.
If your soil test indicates, for example, that it needs more potassium but no additional phosphorus, your soil test will suggest what amendments to add.
If your soil is acidic, such as is best for blueberries and azaleas, but not for cabbage, your soil test results will tell you how to change its pH. If it is alkaline, add garden lime or if it is too low, add garden lime.
If you apply lime or sulfur to your soil, it can take a year or more before you see any change in pH. Plants that tolerate the soil’s current pH do not require a change in pH. Never add wood ash to already alkaline soil.
Typically, soil amendments are used to improve a variety of characteristics of the soil, such as its texture, nutrient content, pH level, or texture. There are two main categories of soil amendments: organic and inorganic.
A variety of organic soil amendments are available, including compost, aged manure, coconut coir, and wood ash.
An example of an inorganic soil amendment is sand, perlite, lime, and vermiculite.
It is important to understand what type of amendment you should apply to your soil based on what it needs:
- Plant material. Plant materials such as leaves, straw, and grass clippings into your soil a few months before you plan to plant them so they have time to decompose.
- Compost. The roots of decayed plants such as vegetable scraps. Worked into the soil at least a few weeks before planting. Excellent soil conditioner that adds nutrients. Can also lower pH levels.
- Leaf mold. Incorporating decomposed leaves into soil increases soil nutrients and structure.
- Aged manure. Use composted manure to enhance soil; make sure it is fully incorporated before planting. Please DO NOT use fresh manures on vegetable gardens, as they can contaminate the soil and cause diseases. Note! Considering that manures contain more salt than other organic amendments, they should be applied sparingly, particularly in dry regions where rainwater won’t leach the salt from the soil.
- Coconut coir. These materials are commonly used as an alternative to peat moss in soil conditioners that help retain water.
- Bark, wood chips, and sawdust. Before adding them to garden soil, these materials should be composted. Otherwise, they will deplete the soil of nitrogen and, as a result, starve the plants of this essential nutrient.
- Cover crops (green manure). In a garden, cover crops are planted after the growing season at the end of the growing season. Since cover crops are a soil improvement technique, they should not be regarded as a soil amendment. During the fall, they grow rapidly, which means they provide substance to the soil in the spring. They typically provide a large amount of nutrients, and their roots can provide structure.
- Topsoil. Replaces existing soil, usually in conjunction with another amendment to provide volume.
- Lime. Raises the pH of acidic soil. Only use after a soil test has been completed.
- Sulfur. Reduces pH in alkaline soil. Only to be used after a soil test.
- Wood ash. Raises the pH of acidic soil. Only use after a soil test has been completed and recommended it to be used.
Amending With Organic Matter
Compost, aged manure, leather, or leaf mold are nutrient-rich organic matter that can be added to poor soil to increase its fertility.
Organic matter is full of benefits! Adding organic matter:
- loosens tight clay soil to improve drainage and aeration, and release minerals.
- bulks up sandy soil to improve its water-holding capacity and nutrient retention.
- makes soil easier to dig and work with.
- moves soil pH towards a level ideal for most fruits and vegetables.
- provides a slow-release form of fertilizer across the season, reducing reliance on commercial fertilizers.
- supplies food for beneficial soil organisms (earthworms, insects, fungi, and beneficial bacteria), which not only convert organic matter into nutrients for plants, but also aerate the soil.
Fixing Different Soil Types
The type of soil in your garden can determine whether it needs amendment, so before you add any amendments, make sure you get a soil test!
Follow these steps to prepare different types of soil:
Sandy soil. If the soil is sandy, it dries out rapidly and does not retain nutrients well. Add organic matter such as compost or well-rotted manure, along with a moisture-retentive material such as coconut coir, and mulch with a natural cloth to retain moisture. Using cover crops and then working them into the soil will also help to provide structure in sandy soils. In subsequent years, mix two inches of compost into the soil each fall.
Clay soil. For amendment, add three to four inches of compost to keep clay soil from becoming clumpy. Every year thereafter, mix an additional inch of compost into the soil in the fall. Clay soil holds too much water, and due to its small particle size, it becomes quickly compacted. Fibrous mulches like straw and fine bark will also add structure to clay soils. Unlike popular belief, amending clay soil with sand will lead to challenging, concrete-like soils. Cut back on tiling. Use raised beds instead.
Silty soil. Silty soils hold water and nutrients, but are more susceptible to erosion. If your soil is silty, add 1 inch of organic material annually to improve the texture. Avoid tilling and compacting the soil as much as possible, or use raised beds.
Loam. If your soil test shows that there is a shortage of nutrients, adding organic matter will improve the soil and give your plants a boost. Loam is a mix of all three soil types and will not require significant amendment.
The addition of too much organic matter can be harmful. Too much organic matter can increase microorganism activity quickly, lowering soil pH and using up available nitrogen. Aim for one-fourth of your soil to be organic matter and thoroughly mix in your existing soil.
How to Add Organic Matter
Organic matter can be added to the soil in the fall. By the spring, worms will have done a great job incorporating most of these ingredients into the soil. If you want to amend the soil during the spring, you can begin as soon as the ground can be worked.
How do you know when the soil is workable?
If the soil crumbles through your fingers or falls apart on its own when you press on it with your thumb, then it is dry enough to work. If the soil forms a ball that falls apart on its own or when you press it with your thumb, then it is dry enough to work. It is suggested to wait several days before checking the soil again, particularly if the ball’s shape does not change with the soil’s moisture.
To add organic matter:
- Put at least 2 inches of organic matter on the soil. Excessive organic matter should be covered with 4 inches of organic matter. Mix the organic matter into the soil with a garden fork. Make sure it is mixed in well and spread evenly!
- Keep adding organic matter to the soil during soil preparation each season; it may require several seasons of amendments before the soil is loamy.
- It’s best to water the soil well after amending it. Check the moisture level afterwards.
- You should wait two weeks after adding organic matter before you plant.
- Before planting, rake the soil clean and level it. Remove all fallen sticks, rocks, and other material. Now you’ll be ready to plant!