The healthy garden soil is absolutely essential to a successful garden. Without rich, healthy soil, your careful efforts at sewing, planting, tending your garden will be in vain. Soil provides the nutrients, water and some air needed for plant growth and development, so it’s worth spending time trying to improve its quality. Moreover, when garden soil is fertile and nutrient-packed, there is less need for fertilizers, pesticides or herbicides. Reducing or eliminating the need for these chemicals not only benefits our health, it can also help protect the environment in numerous ways.
Learning about the soil and ways to make healthy soil will help you to produce the healthiest food. And also makes you a much better gardener.
Table of Contents
What makes healthy soil?
Soil texture is a good place to start when you look at you garden soil. Understanding your soil’s texture helps you know more the possible restrictions on your particular site as well as any advantages. Which means you can make informed decisions about plant choices, irrigation design, and soil improvement measure much more easily.
Soil texture is the percentage of sand, clay and silt particles a particular soil has.
- Sand has the largest particles, visible to the naked eye. Sand drains so well and does not compact easily. Water, air, and roots can move freely in sandy soils, sometimes too much so.
- Silt particles are much smaller than sand and they are irregularly shaped like sand particles. They make soil feel slippery.
- Clay particles are microscopic and make soil feel smooth. They pack together tightly, leaving little to no room for water, air or roots.
Texture has an important influence on the soil’s:
- water and nutrient-holding capacity
- root penetration
- susceptibility to erosion.
How Do I Tell What Texture My Soil Is?
You don’t need to be an expert to determine your soil texture. You can determine your soil texture by making a ball of damp garden soil. If it falls apart easily when you rub it in the palm of your hand, it’s a sandy soil. A silt soil will form a ball, but it will crack when you try to roll it out into a ribbon. If you can make it a long ribbon, you have mostly clay.
Sandy soils have a tendency to drain so well – water and nutrients rapidly drain through the soil, often before plants have a chance to absorb them. For this reason, these soils are usually nutrient-poor. Clay soils often have the opposite problem – can be hard to work and slow draining.
You can use compost as a treatment for both problems. The organic materials in the compost act as a sponge, holding water and nutrients in the soil for plants to access them. For the clay soils, it opens up the porous structure allowing water to move around.
It’s also important to note that soil texture cannot be changed. It is impossible to sift out individual and, silt and clay particles to make a practical difference in your particular piece of land. Also, don’t try to change your soil texture by adding clay to sand or vice versa. It is best to work with what you have and improve other aspects of a given soil.
Whereas the texture of the soil is the relative proportion of three soil particle types (sand, silt, and clay), the structure of the soil refers to the arrangement of these soil particles into units of different sizes and shapes and the pore spaces that are left between them (also called soil aggregates). They are bound together by chemical, physical, and biological processes.
While the soil texture is inherent and difficult to change, so to build high-quality soil, we can influence the soil structure with our soil improvement measure. When we plow, lime, add organic material or stimulate biological activity, we change our soil structure.
As mentioned above, sandy soils have good drainage but the low organic material and low clay content, so aggregate stability is often difficult to maintain. In contrast, clay soils have large aggregates that there is insufficient pore space to allow root hairs to grow between them.
Horticulturally speaking, the structure of the soil can be “good” or “bad” and can be improved or degraded by how we use the soil. Soil structure can be blocky, columnar or structure such as a massive clay soil. A good soil structure is soft and crumbly that has a wide range of pore spaces or empty space between the soil particles. This produces a good network of soil pores that have good drainage and aeration that allows for rapid exchange of water and air with plant roots.
Generally, the increased structure is related to texture and enhances the availability of oxygen and water to roots and facilitates root penetration.
There are two basic ways to improve soil structure.
- Organic matter – compost and mulch – can improve any type of soil. It enriches the soil and provides food for the soil-dwelling insects.
- Preventing compaction and disturbance of the soil.
It’s worth mentioning that tilling is a double-edged sword. Although it can help loosen soil structure, repeated tilling destroys aggregates and kills the insects living there. Depending on the site, the existing soil structure will need improvement. A simple test of soil structure called the slake test is outlined in a publication from the USDA Natural Resources Conservation Service (NRDC). Consult a soil science specialist for further details.
Soil water-holding capacity water is simply the amount of water that a given soil can hold between field capacity – the time it is fully saturated but drained and the permanent wilting point (it is so dry that plants die).
The water-holding capacity is also one of the most important characteristics of healthy garden soils. Soils that hold a lot of water are less subject to leaching losses of nutrients and pesticides. This is true because a soil with a limited water holding capacity (i.e. sandy soils) is saturated with water much sooner than a soil with a high available water holding capacity (i.e. clay soils). After a soil reaches the saturation point, all of the excess water and some nutrients in the soil are leached into groundwater or waterways.
Sandy and clay soil will have different water holding capacities. As you may know, sandy soils will not be able to store as much water for crop use between rains. Since soil water holding capacity is controlled primarily by the soil texture and the soil structure, it’s important for gardeners and farmers to understand the soil structure and how to manage it so that the garden/farm does not need to suffer from a drought or irrigate.
Generally, the higher the percentage of clay and silt particles, the higher the water holding capacity. The amount of organic matter in the soil also influences the available water holding capacity due to the affinity of organic matter for water. When the level of organic matter increases in the soil, the soil water holding capacity also increases. By adding the stable organic matter – such as compost, manure, cover crops to soils, you can significantly improve the water holding capacity of your soil. In the long term, you may want to consider rotation to sod and reduced tillage.
Soil nutrients come from many sources including decaying organic material, soil organisms, and fertilizer. Soil nutrients which require by plants include:
- Primary (macro) nutrients: nitrogen – is largely responsible for healthy leaf and steam growth, phosphorus – very important for root growth and potassium – is needed for overall plant health.
- Secondary nutrients: calcium, magnesium, sulfur.
- Micronutrients : boron, chlorine, copper, iron, manganese, molybdenum, and zinc.
A soil lab analysis will help you understand more about your soil nutrients. Keep in mind that nitrogen – which is essential to plant health and growth, is extremely mobile, so a soil test will only give you a snapshot of the nitrogen levels present on the day of sampling. A competent gardener can also get an idea of possible nutrient deficiencies or sufficiencies by observing the health of plants in the garden.
Soil pH is a measure of the soil alkalinity or acidity. The pH scale commonly in use ranges from 0 to 14 with 7 as the neutral mark, decreasing with rising acidity and increasing with rising alkalinity. The scale is logarithmic, so a pH of 5 is 10 times more acidic than a pH of 6, but a pH of 5 is 100 times more acidic than 7.
Why does soil pH matter?
The reason soil pH matters is that most nutrients in the soil are only available to plants if the soil pH falls into an acceptable range. For example, Potassium, sulfur, nitrogen, iron, magnesium are are are available along with a broader range of acidity, while the availability of manganese, boron, zinc, copper, phosphorus lessens as alkalinity increases.
Most plants prefer a pH of 6.2 to 7 (slightly acidic to neutral), which is also where soil nutrients are most available. Some plants are more specific in their requirements. Some “acid-loving” plants can grow in the soil which has a pH as low as 5.5, and some can grow above 7.5.
Additionally, soil pH influences microorganic activity that contributes to the decomposition process of organic matter. A neutral pH is ideal for microbial activity that reflects microbiological processes of soil microorganisms as plants rely on soil microorganisms to mineralize organic nutrients for growth and development.
Since soil pH is essential to plant growth, testing pH levels is important, especially when growing a garden for the first time in new soil whose acidity is unknown. If the soil pH is not within a certain range for the plants you are growing, the plants will not be able to get the nutrients in the soil, no matter how much you feed them. This can be done using a home kit or you can bring a soil sample into your local country extension, to be tested for a nominal fee.
Once you know what your soil pH is, you can begin to adjust it slowly. Depending upon your soil and test results, you can add some form of sulfur to lower the soil pH and form of lime to raise it. Also, remember that it can take months to moderate the pH of your soil and then it requires a little effort every year to maintain it.
Again, adding organic matter every year can help balance the soil out whether it is acidic or alkaline. Lime or sulfur may be used to moderate the pH of the topsoil layer but will do nothing to alter the subsurface pH. Moreover, clay soils have a high resistance to changes in soil pH so more amendment may be needed than is practical. Sometimes, it is easier to simply choose the plants to suit your soil pH – a local horticulturalist can be very helpful.
Steps to Improving your garden soil
1. Soil Testing
The first step to improve your soil’s quality is understanding what you have to work with. Good crop production often requires the application of organic matter, lime, and fertilizer. A soil test can help you know each of the following attributes of the soil.
- Current pH levels of your soil
- Some soil tests even detect the amount of organic matter
- Type and quantity of lime your soil needs
- Fertility levels of the principal nutrients
- Nutrients need to be added to your soil
- Amount of fertilizer your soil needs
Know the exact nutrient levels in the soil allows us to amend the soil properly for the best crop production possible.
2. Supply What’s Missing
After testing your garden soil, you can determine your garden’s fertilizer needs. Commonly, after years of soil building and planting, the organic soil recycles and retains most nutrients, that helps reduce or eliminate added fertilizer needs. But when growing a new garden, you want to add a certain amount of fertilizers and lime to make sure proper nutrition for the season ahead. If you’ve missed the fall window to supply fertilizers and lime, add them a couple of weeks before plating in spring.
3. Adjust Soil pH
Once you have your garden soil tested, you will know whether you have a soil pH imbalance. If your soil is alkaline, you will get a recommendation for adding gypsum, sawdust, composted leaves or elemental sulfur to lower the soil pH. If it is too acidic, using limestone, bone meal or crushed oyster shells to raise the alkalinity. This is easy enough to do and should be done in stages, so as not to shock your plants.
4. Adjusting Soil
Most of us are not blessed with a perfect soil naturally. Your garden soil might be too sandy or too clayey. As I said, it’s impossible to change the soil texture, but we can improve our soil quality by influencing our soil structure – it just takes some time to properly adjust soil.
And the easy and affordable way is to mix organic matter into the soil and mix well. Since it takes time for the decomposition process to occur, this technique is best exercised in the autumn. Some people even add liquid nitrogen to the mixture to speed up the decomposition process.
Adding high-quality organic potting soil is another way to improve your soil while it helps promote strong root development and plant growth. You may want to mix potting soil at least 8″ – 12″ deep into existing soil. It may take some work but it is worth the effort when your garden begins to take off in the high-quality soil.
Also, try to avoid stepping or pulling wheelbarrows over your garden bed as much as possible since it is one of the best ways to destroy the soil structure. Stepping in the garden beds is the main causes of soil compaction – making it more difficult for plant roots to grow.
5. Adding organic matter
I’ve said it before and I will say it again now: Organic matter is the single best thing you can do to improve soil quality right now.
Whether your soil is sandy, clayey, low in nutrients, has poor drainage, compacted…organic matter can help.
According to PennState Extension “Soil organic matter (SOM) is a complex of diverse components, including plant and animal residues, living and dead soil microorganisms, and substances produced by these organisms and their decomposition. SOM influences the chemical, biological, and physical properties of the soil in ways that are almost universally beneficial to crop production. The most common sources of SOM in farming are crop residues, cover crop residues, manures, and composts.”
That said, adding organic matter to the garden soil improves the soil structure, increases the available nutrients, and feeds the beneficial microorganisms and insects in your soils. These little guys can feed on harmful microbes like certain soil born diseases and nematodes. They also provide some nutrients into the soil when they die. So the more beneficial microorganisms your soil can support, the more nutrients will be in the soil and the less bad organisms will survive.
So what should you be adding to your garden soil? Compost is highly recommended.
Not only is compost full of organic nutrients that will improve your soil immediately, but the composition of well-made compost provides better water drainage and aeration in just about every type of soil imaginable.
Compost can be used in your garden beds at any time, either turned into the soil or top dressing for established plants. You can add it to your garden soil at the beginning of the planting season and side-dress your plants with compost throughout the growing season.