Vegetables need good soil for healthy growth and harvests. Well-prepared soil is the foundation of your entire garden—and gives you a jump-start on the season! In our guide to soil preparation, we’ll help you get to know your soil type, teach you how to improve your garden soil quality, and give your plants the very best start!
Gardening does not start with a seed in the ground. It starts with the soil. You can’t have healthy, productive plants without rich, soft soil that allows the roots to grow deep enough to soak up nutrients.
The good news? You can improve your soil with compost and organic matter. Rich soil literally has a life of its own with micro-organism activity (such as earthworms) that break down matter to release essential nutrients that plants need. Soil enriched with organic matter holds onto nutrients and moisture but drains well, loosens soil to create more oxygen for plants, and stablizes and anchors plant roots.
Spring Soil Prep: 3 Easy Steps
The last thing we want to do is overwhelm the beginner gardener! While we’re going to really “dig in” to full soil preparation below, here are 3 basic steps for spring:
- Clear out rocks and debris. To dig up grass, use a spade to cut the sod into small squares and pry from the planting area with the end of the spade.
- Loosen the soil. If it’s your very first garden, loosen soil to a depth at least 8 inches (12 is better) so that roots can reach down.
- Adding Organic Matter: This spring, if all you do remember is to add organic matter such as compost, that will get you off to a good start! Add on a day when the soil is moist but not wet.
- Spread a minimum of 2 to 3 inches of compost or aged manure onto your soil (and no more than four inches).
- Many gardeners will dig the organic matter into the soil.
- However, there’s also a no-dig philosophy to expose fewer weed seeds and not disturb the soil structure; simply leave the compost on the surface. Let the worms do the digging in for you!
- To us, it really depends on the shape of your soil. In year one, if you have poor soil, we’d work in the compost. Or, if you have hard, compact soil, consider building a raised bed. Or, you could grow in planters and containers.
- Level the garden bed with a steel garden rake before planting.
A couple other tips:
Warming Your Soil: If you live in a colder region, consider a raised garden bed to help wet, cold soils dry out and warm up more quickly. You can also cover your beds before planting with black plastic to cardboard to block light and protect it from snow, rain, and erosion.
Clearing Out Weeds: One method to get rid of weeds early—before planting time—is to lightly disturb the soil surface, then warm up the soil using sheets of clear plastic. Once the weed seedlings are up, pull them out or remove them with a hoe. Don’t dig up the soil, which will just bring new weed seeds to the surface—the idea is to just remove those that are already at the top.
Once you build a foundation of rich, dark, fertile soil, gardening will be “easier” the rest of the year and every year going forward!
Digging Deeper: Know Your Soil
So, let’s learn more about YOUR soil and how it affects how plants grow. Do you have clay or sandy soil? Is your soil acidic or alkaline? Is it thin or rich in nutrients? We’ll review three important components:
- Soil Type
- Soil pH
- Soil Nutrition
I. Soil Types
All soil is a mix of rocks that break down over time, mixed organic matter (dead plants and animals), and other microscopic things that plants need to survive.
There are three types of rock particles: large (sand), medium (silt), and small (clay). Usually, soil is a mix of these particles. The mix of particles will affect:
- How water drains. Clay soil drains slowly and holds too much water. Sandy soil does not hold enough water, as it flows through too quickly.
- How much oxygen plant roots get. Clay leaves little space if it gets compacted.
- How well the soil holds nutrients. Clay has tiny particles that hold nutrients, as does silt. With sand, nutrients flow through too quickly.
- How quickly the soil will erode. Clay is sticky and sand is heavy, but light silt particles are more prone to erosion.
Very fine particles are slow to absorb moisture or to drain. Clay soil holds its shape when rolled into a ball. It can bake hard in summer and become waterlogged in winter.
Large particles that drain quickly. Sand does not hold onto nutrients very well, but warms up quickly in spring.
Smaller particles than sandy soils. A slightly slippery, floury feel. Holds onto moisture and nutrients for longer.
The perfect balanced soil is called “loam”
The ideal soil texture consists of equal parts of sand, silt, and clay; this type of soil is referred to as “loam” or “loamy.” Loamy soil has that perfect balance—it holds moisture but also drains well, allows oxygen to reach plants’ roots, and is rich in humus (organic matter). It’s fertile, easy to work, and contains plenty of organic matter.
Good garden soil crumbles easily. It will not form a hard ball when squeezed nor crack or crust over when dry.
So, how do you find out how much sand, silt, or clay is in your soil?
- The simplest and most generic method is the feel test; rub a moist sample of soil between your fingers. Sand will feel gritty, silt smooth, and clay sticky.
- Another test is the ribbon test; with this test, squeeze a small, moistened ball of soil between your thumb and forefinger to create 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.
- There are other tests you can do at home such as the jar test.
II. Soil pH
Whereas soil type was about particle size, soil pH is about nutrition and soil fertility. Soil pH affects plants’ growth because it affects the availability of nutrients and minerals in the soil, as well as how well a plant can access, absorb, and regulate these materials. A very high or very low soil pH will result in nutrient deficiency or toxicity, leading to poor plant growth.
A pH ranging from 6.0 to 7.0 is ideal for most garden vegetables. This is the ideal range when microbial activity is greatest and plant roots can best access nutrients. However, many plants tolerate a wide range and certain plants have specific pH range preferences. Find a list of common garden plants and their pH preferences here.
Availability of Nutrients at Varying pH Values
III. Soil Nutrition
To quickly review, plants’ primary nutrients are nitrogen (N), phosphorus (P), and potassium (K). On the package of a fertilizer, you’ll see these three values separated by dashes (N-P-K); the numbers of each nutrient indicate the percentage of net weight contained.
- Nitrogen (N) promotes strong leaf and stem growth and a dark green color, such as desired in broccoli, cabbage, greens and lettuce, and herbs. Add aged manure to the soil and apply alfalfa meal or seaweed, fish, or blood meal to increase available nitrogen.
- Phosphorus (P) promotes root and early plant growth, including setting blossoms and developing fruit, and seed formation; it’s important for cucumbers, peppers, squash, tomatoes—any edible that develops after a flower has been pollinated. Add (fast-acting) bonemeal or (slow-release) rock phosphate to increase phosphorus.
- Potassium (K) promotes plant root vigor, disease and stress resistance, and enhances flavor; it’s vital for carrots, radishes, turnips, and onions and garlic. Add greensand, wood ashes, gypsum, or kelp to increase potassium.
Learn more about NPK Ratio: What Do Those Numbers Mean?
A soil test will provide information about the level of nutrients available. Depending on the soil test you choose, phosphorus, potassium, magnesium, and calcium are the most common nutrients you will receive information about.
Get a Soil Test
It’s a good idea in the spring (or fall) to send of a soil sample for testing. That way, you’ll know if you need to add lime or sulfur to adjust pH.
As well as pH, a soil test will also tell you your soil type, what nutrients are missing, and how to improve your soil. Most university extension services provide soil testing for home gardeners. You can also probably purchased kits in garden stores or online. You just dig up a small amount of soil from a few places in your garden.
- In terms of nutrition: You may find, for example, that your test indicates that your soil needs more potassium but absolutely no additional phosphorus. Your soil test will recommend what amendments to add.
- In terms of pH: Perhaps you find out that your soil is too acidic (which is great for blueberries and azaleas, but not cabbage). Your soil test results will make recommendations to adjust your soil pH. If your soil pH is too low (acidic), add garden lime to the bed. If your soil pH is too high (alkaline), add powdered sulfur to the soil.
Raising and lowering your pH does take time; once lime or sulfur is applied, it can take a year or more to see any movement in pH. Remember, you do not have to change your soil pH if you grow plants that tolerate the current pH of your soil. And never assume that you should add lime, sulfur, wood ash, or other amendments. Don’t make already alkaline soil even more alkaline with wood ash!
Improving Your Soil
Soil amendments are materials that are added to the soil in order to change it in some way. Often, they are used to improve the soil’s texture, nutrient content, or pH level. Amendments can be divided into two main categories: organic and inorganic.
- Organic soil amendments include things like compost, aged manure, coconut coir, and wood ash.
- Inorganic soil amendments include things like sand, perlite, lime, and vermiculite.
Which amendments you use depends on what your soil needs. Here are some of the most common amendments and their functions:
- Plant material: Leaves, straw, and grass clippings. Work material into the soil several months before planting to allow it time to decompose.
- Compost: Decayed plant materials such as vegetable scraps. Work it into the soil at least a few weeks prior to planting. Excellent soil conditioner that adds nutrients. May also lower soil pH.
- Leaf mold: Decomposed leaves that add nutrients and structure to soil.
- Aged manure: A good soil conditioner. Use composted manure and incorporate it into the soil well ahead of planting. Do NOT use fresh manure on vegetable gardens, as it can damage plants and introduce diseases. Note: Manures contain a higher concentration of salts, so use them more sparingly than you would other organic amendments, particularly in dry regions where salts won’t be leached away by rainfall.
- Coconut coir: A soil conditioner that helps soil retain water. This material is a more sustainable alternative to peat moss.
- Bark, wood chips, and sawdust: These materials should be composted before being added to garden soil. Otherwise, they will rob the soil of nitrogen and, consequently, starve the plants of this essential nutrient.
- Cover crops (green manure): Cover crops are more of a soil improvement technique than a soil amendment. Cover crops (such as clover, rye, or oats) are planted in the garden at the end of the growing season. They grow rapidly in the fall and are then worked into the soil in the spring. They often contain an abundance of nutrients and their roots can provide structure. Read more about using cover crops.
- Topsoil: Usually used with another amendment to provide volume. Replaces existing soil.
- Lime: Raises the pH of acidic soil. Only use if recommended by a soil test.
- Sulfur: Lowers the pH of alkaline soil. Only use if recommended by a soil test.
- Wood ash: Raises the pH of acidic soil. Only use if recommended by a soil test.
Amending With Organic Matter
As discussed above, the best way to make poor soil into perfect soil is to add nutrient-rich organic matter such as compost, aged manure, or leaf mold.
The benefits of organic matter are countless! 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
Once you know which type of soil you have in your garden, you can amend it properly. Remember, before adding any amendments, it’s a good idea to get a soil test done!
Here’s how to tackle each type of soil:
- Sandy soil: Sandy soils dry out very quickly and don’t retain nutrients well. To fix this, work in 3 to 4 inches of organic matter (such as compost or well-rotted maure), as well as a material such as coconut coir, which will help with moisture retention. Mulch to retain moisture. In subsequent years, mix 2 inches of compost into the soil each fall. Using cover crops and then working them into the soil can also help to provide structure in sandy soils.
- Clay soil: Clay soils hold too much water, and the small particle size of the clay allows it to quickly become compacted and clumpy. To amend clay soil, start by adding 3 to 4 inches of compost to make it more workable. Each year thereafter, mix an additional 1 inch of compost into the soil in the fall. Fibrous materials such as straw or fine bark mulch will add more structure to clay soils, too. Contrary to popular belief, amending clay soil with sand will only result in tough, concrete-like soil! Minimize tiling. Or, just use raised beds.
- Silty soil: Silty soils hold water and nutrients, but are more susceptible to erosion. If you have silty soil, add 1 inches of organic matter every year to improve the texture. Avoid tilling as much as possible and compacting the soil. Or, just use raised beds.
- Loam: Loam is the ideal mix of all three soil types and will likely not need significant amending to get it ready for planting. Nevertheless, if a soil test does show a lack of nutrients, adding organic matter will improve the soil and give your plants a boost.
Too Much of a Good Thing
As with anything, adding too much organic matter can be detrimental! Too much organic matter can rapidly increase microorganism activity, which uses up available nitrogen and affects soil pH. Aim to have organic matter make up about ¼ of your soil mixture overall and thoroughly mix it into your existing soil.
How to Add Organic Matter
Ideally, you’ll add organic matter in the fall. By the spring, worms will have done a great job incorporating most of that organic matter into the soil. If you are looking to amend your soil in the spring, you can do so as soon as the soil is workable.
How do you know when the soil is workable?
Take a handful of soil from a depth of about 6 inches and squeeze it in your hand to form a ball. If the soil crumbles through your fingers, 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 the soil is dry enough to work. However, if the ball retains its shape or your thumb just leaves an indentation, the soil is too wet to work. Wait a few days and check the soil agan.
To add organic matter:
- Pour enough organic matter on your garden so it can be spread to a depth of at least 2 inches. Do not add more than a 4-inch layer. With a garden fork, mix the organic matter into the top 6 to 8 inches of existing soil. Make sure it is well combined and spread evenly!
- Continue to add organic matter each season during soil preparation to build and maintain the soil. Be patient; it may take several seasons of amendments until the soil is loamy.
- After amending the soil, it’s best to water well and then check the soil moisture.
- Let a window of at least two weeks pass between when you add organic matter and when 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!
A Note on Raised Beds
If you’re struggling with your soil, another option is raised garden beds. With raised beds, you control the soil that you put in the bed. Whether you decide to plant directly in the ground or in a raised bed, make sure that you don’t walk on your newly amended soil or it will get compacted. The general rule is to make sure a bed is no wider than four feet—or has a garden path—so that you don’t walk on the soil. See how to build a raised bed.
Raised beds also help in colder climates to advance your growing season by a couple weeks. Speed things along by covering the beds with something light-blocking and non-porous like black plastic anchored down with rocks. If you’re not keen on plastic, you could lay old salvaged windows over the bed. At minimum, we like to cover our beds with cardboard or old carpet remnants to keep weeds from growing.
Free Online Gardening Guides
We’ve gathered all of our best beginner gardening guides into a step-by-step series designed to help you learn how to garden! Visit our complete Gardening for Everyone hub, where you’ll find a series of guides—all free! From selecting the right gardening spot to choosing the best vegetables to grow, our Almanac gardening experts are excited to teach gardening to everyone—whether it’s your 1st or 40th garden.
Got an over-spent or neglected field you want to turn into a garden? Read our article about reclaiming your garden soil.