Garden Soil

Garden Soil: Know Your Soil!

Building healthy and fertile soil is the basis of all organic gardening. By discovering the unique characteristics of your home garden, you can learn how to optimize the potentials of your soil, and grow the best herbs and vegetables that your garden can. You can start by understanding soil in general, and your own garden soil, in particular.

Organic gardening principles

Healthy soil for organic gardening is built in ways that develop and protect its structure, its fertility, and the millions of organisms that make soil their home. Caring for the soil involves the use of organic residues, in the form of waste plant materials and animal manures.

Maintaining soil health employs methods that use fertilizers and amendments judiciously and minimize the presence of soil-borne diseases with crop rotation and selective planting.




What is soil?

Soil is a living system – an ecosystem – composed of four elemental parts: minerals, gases, liquids, and organic life.

  • Minerals are present in the form of soil particles, formed from the weathering of native rock and plant materials.
  • Gases, particularly atmospheric gases, reside in the spaces between soil particles and provide essential nutrients, such as Nitrogen, to the plant roots.
  • Liquids, mostly water and water-soluble minerals also are present in the pores between soil particles. These too transport critical minerals and nutrition directly to plant roots.
  • Finally and perhaps most importantly, are the vast arrays of micro- and macro-organisms present in healthy soil. This group includes bacteria, fungi, nematodes, protozoa, arthropods, worms, and burrowing animals, which form the food chain that fuels all the major processing functions of garden soil.


Soil types

Different types of soil are classified by methods which essentially describe how they look and from which materials they were formed. Soil scientists use a classification system which divides all the various soils into 12 categories. Each category references the parent rock, the weathering processes involved, the presence of organic materials, and the saturation of the soil with water.

More practical for garden soil, is the simple classification system based on soil texture. This system depends on the relative amounts of each of the major kinds of soil particles; sand, silt, and clay.


Soil life

Garden soil is opaque to our eyes, but it is full of life. The micro-world hidden between soil particles is teeming with living things, from bacteria to earthworms. This world of prey and predators is a complex food chain that forms a critical web of life for your garden. They decompose organic matter; enhance soil structure; promote root growth; modulate populations of soil pathogens and plant diseases; and makes essential nutrients available to plants. Conventional farming and gardening practices tend to diminish the population of this essential life-force. Organic methods, on the other hand, enhance the soil to sustain healthy populations of soil micro-organisms.


Organic matter & your soil

The hallmark of healthy garden soil is its abundance of organic matter. Its importance cannot be overstated, since organic materials in your soil provide so much benefit. It is the primary fuel for the complex ecosystem of soil micro-organisms. It creates a more open and porous soil texture, maintaining good drainage and transport. It helps the soil retain water like a sponge and helps keep the soil moist and cool. And it mitigates excessive soil acidity and alkalinity.


Tilth: healthy soil structure

A soil that absorbs water quickly and drains well, and does not crust over or form clods is said to have good tilth. Tilth is the physical condition of garden soil as it relates to seedbed quality, easy seedling emergence, deep root penetration and ease in digging.

Good tilth is dependent on aggregation – the process whereby individual soil particles are joined into clusters or “aggregates”. A well-aggregated soil allows for increased water entry, increased air flow, increased water-holding capacity, and resistance to soil erosion.






Testing your soil

Do you have healthy soil in your garden? How do you know?

You can learn a lot by simple observation. If your soil is compacted, water will soak in slowly; it will be hard to dig, and plant roots will tend to spread sideways rather than downward.

Look for earthworms, soil insects, and vigorous roots. This gives you important clues to your soil’s composition.

While observation will show you much about your garden soil, there is more still that cannot be seen. To determine the levels of essential plants nutrients, soil acidity, and the need for amendments, you will need a soil test.

You can buy a test kit for home use, which will give you useful if rudimentary results. Or you can send a sample to one of the many reputable soil laboratories.

The process is simple, inexpensive, and essential if you want to grow the best vegetables in the most healthy soil.


Soil Chemistry: ph

References to soil chemistry usually describe the alkalinity or acidity, or pH (potential Hydrogen), of soils. The full scale of pH ranges from zero to fourteen, with seven being neutral. Values below seven are considered acidic; number higher than seven are alkaline. In garden soil, the pH is important because the range in which plants can easily grow is limited. Too acidic or too alkali, and essential plant nutrients become chemically bonded to soil minerals and are not available for plant growth.

All life on Earth is rooted in the soil. In turn, healthy soil allows life to flourish. As an unbreakable part of the food chain, plants link all living things, directly and indirectly to the earth. Building and maintaining healthy and fertile soil is the fundamental basis of organic gardening.


Balancing ph

If your garden soil is too acidic or too alkaline, you will have difficulty growing vegetables and herbs. Plant life has adapted to a wide range of acid and alkali soils throughout the world, but garden plants can thrive only in a much narrower range. The acid-alkali scale measures the amount of possible Hydrogen ions present in the soil. The greater the amount of potential Hydrogen, or pH, ions the more acidic the soil.


The pH scale ranges from a low of zero (0) to a high of fourteen (14). The midpoint value of seven (7) is considered neutral. Numbers lower than seven indicate progressively more acidity as they approach zero. Conversely, numbers higher than seven are progressively more alkaline as they approach fourteen.

Garden plants require healthy soil with a pH of 5 to 8 to grow well, so balancing the pH in your garden soil is essential to strong plant growth.


Soil amendments & organic fertilizers

Armed with the knowledge that you have gained from the soil tests, you can begin actually build healthy soil. The full soil test has given you a baseline measurement from which to start. If your soil pH is low, you now know that it needs to be corrected, and by how much. If your soil lacks sufficient Phosphorus, you can plan to add the proper amendments and in the proper amounts. If your soil is deficient in specific trace minerals, you can judiciously apply the specific organic fertilizers to address the problem.


Creating well balanced, fertile and healthy soil is simple, and can be achieved in a number of ways. Spending the time and energy on testing and balancing the soil will more than pay for itself in the results, vigorous and bountiful plants.



Fertile healthy soil is at the heart of organic gardening, and composting is the primary means by which organic gardeners achieve their amazing results. This is where learning from nature and employing natural process comes to fruition in the garden. By taking normal waste products, such as plant materials and animal manures, and hastening their decomposition, the organic garden creates one of the most valuable substances known to humanity, compost.


Compost is a substance with seemingly magical qualities. It can neutralize excessive pH, retain moisture in the soil, and encourage the presence of soil building organisms such as earthworms.


Earthworms & vermiculture

In the animal kingdom, worms are the kings of composting. They simply eat all of the kitchen scrapes and garden waste that we give to them and excrete an amazingly rich form of compost and fertilizer as their “castings”.

In addition to building a compost heap to process massive quantities of plant waste and animal manures, building a worm bin is the next best addition to your garden. Worm culture, or vermiculture, is the process of creating a comfortable home for worms; feeding them judiciously with rich succulent food, like kitchen waste; and harvesting the nutrient rich castings and liquid (worm juice) that they produce. Read More


Cover crops

One lesser used method of building healthy soil is by growing plants. More specifically, it is the growing of certain plants at certain times. When the soil is bare, a crop meant to cover and protect the soil is helpful in maintaining good soil texture, in reducing compaction, and preventing erosion from wind or rain.

Known as a cover crop, or green manure, this layer of plants is grown for a portion of the season and tilled into the soil prior to planting. This practice increases the amount of organic matter in the soil and draws soil nutrients up from deep in the ground to you garden soil.

There are a variety of cover crop plants and a variety of methods used to build, maintain fertility, and improve the chemical balance of your soil. Read More



In much of the country, water is a precious resource that must be used wisely. Each type of plant in the garden has a specific need for water, an essential amount that cannot be compromised. How much water you need and how you apply it will vary widely depending on your climate, the characteristics of your particular soil, the time of day you water, and the quality of the water available to you.


In a hot dry climate, you will want to apply water sparingly and apply it directly to where it is needed. If your area has warm and humid days, you will choose to avoid wetting the leaves as you water, to minimize the spread of fungal diseases. In each case, watering methods should reflect what you grow, your seasonal weather, and the particulars of your garden.


Weed control

Weeding can be a difficult frustration chore or an easy once-in-a-while task, depending on how you construct your garden. If you have built healthy soil, with a soft fluffy texture and good tilth, then pulling a weed is a simple tug that removes the offending plant, roots and all.

Hard, dry and compacted soil will not only encourage weeds to grow by giving them an advantage over move supple, less tenacious vegetables, but will make weeding a harder and less successful chore. Do you prefer the former course of action over the latter?



The simple act of mulching, the application of a protective layer on material on the soil surface, acts to create healthy soil in five ways. Mulch modifies soil temperature, keeping it cool on a hot summers day thus preventing heat damage to tender root tissue. Mulch reduces evaporation, keeping the soil moist and water available for garden plants. A layer of mulch protects the soil from drying and crusting, and helps to maintain healthy soil structure. The growth of weeds is suppressed by mulching, making weed control simple and easy. And organic mulch, as it decomposes, adds new components to the soil, building up its fertility.



Cultivation, or tilling, of the soil is a necessary part of forming good soil structure, texture and tilth. Done properly it can mitigate compaction, improve drainage, and help to encourage soil

soil for organic gardening



However, cultivating certain types of soil at the wrong times can destroy the structure of the soil, which may take years to correct. For example, tilling a heavy clay soil too early in the spring can actually reverse the intended effect and increase crusting and compaction.

The clay, when it dries, may form into large rough and impervious clods that cannot 

be reworked to sow seeds.


Crop rotation

During and after the growing season, the process of growth and decay leaves a measurable amount of residue in the soil. Each process has a specific chemical signature and leaves behind certain byproducts in the soil, such as mold spores, trace minerals, and plant waste. If the same annual plants are grown in the same spot year after year, this residue can build up.

While not always a problem, these byproducts can encourage the growth of fungal and bacterial diseases, which are ‘customized’ to attack the specific plants that have been grown there in years past. By employing crop rotation, this pattern is disrupted.

Grow different crops in the same spot, or plant the same plant in different spots each year, in effect, rotates the crops from place-to-place. The potential for plant diseases are minimized and you will continue to maintain healthy soil.