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Garden Soil Amendments

What You Should Know About Soil Amendments

The good health of all garden plants doesn’t come down to fertilizer or watering. Plant health is only as good as the soil they are planted in.

A good soil is the very foundation of a healthy garden.

Often, however, the soil that is present in a yard isn’t healthy enough on its own to meet the nutrition requirements of garden plant.  This is especially true of new construction sites where all or most of the top soil has been stripped away as the home is being built.

Although, the general contractor replaces the topsoil as they regrade the entire yard it is inevitable that some of the nutrient deficient clay or sand subsoil has gotten mixed in during this process.

It is up to the gardener to rebuild and restore the soil before they can cultivate plants.  This is where the addition of soil amendments come in.  

Soil amendments are the organic compounds blended with existing soil to create an optimum growing environment.

Before you proceed you’re going to know exactly how healthy the soil is as it presently stands to know what organic matter to add or how much you’re going to need.

Test the soil first

It is a good idea to test the soil before you put a shovel in the ground. Plants require three main nutrients and numerous trace elements and it is highly likely that you are deficient in more than one of these.

The first step is to drop by the hardware store or garden center for an inexpensive test kit designed to analyze where your soil is at when it comes to the big three.

  • Nitrogen
  • Phosphorous
  • Potassium

Collectively these nutrients are known as NPK and they each serve a valuable service.  

Nitrogen acts on the upper portion of the plant that is above the soil line. Too much nitrogen and the plant foliage will grow at a rate much faster than the root system can support.  An overfed plant will also not produce any blooms or fruit.

Phosphorous increases the blooms and helps produce healthy fruit or vegetables.

Potash is the core nutrient for a lush root system and strong stem growth. A potash deficiency will result in weak roots that are unable to support the plant and droopy, sickly stems.

A little nitrogen goes a long way, so the best garden fertilizers will be slightly lower in this nutrient but will be higher in phosphorus and potash.  The exceptions to this are heavy feeders like cold crops, lettuce or cauliflower.

Fertilize only as you need it

We always want to be mindful of the environment and keep in mind that overfertilizing isn’t going to help the garden, so use the amount you need. An excess is only going to leach away and add to the contamination which is already a major problem and none of us want to contribute to that.

Testing the pH

You will also need to know what the acidy or pH of the soil is before you plant, as well.  There is no need for the home gardener to purchase an expensive pH meter and a simple method of testing is available at any hardware store.

The pH scale measures acidity of the soil using a numeric system ranging from 1-14. A pH rating of 7 is considered neutral and any ranking above that is considered acidic soil while anything below is alkaline.

Most garden plants do best with a neutral to slightly alkaline pH at a reading of about 6.5 to 6.8.

Growing a healthy garden isn’t simply a matter of nutrients and adding fertilizer to achieve this. Good soil health also includes a healthy body or texture that roots can easily penetrate and grow in without struggling.

A handful of healthy, rich soil should clump easily, but break down again with a light closing of the hand.  A heavy or clay soil will only clump tighter with a grip while a loose or sandy soil won’t clump at all because there is nothing binding it together.

Now that you where your soil is at nutrient and body wise it is time to start building and improving soil health through additives.


Compost is any organic matter that has decomposed.

Some good compost matter would include leaves, peat, old plants or bark. These break down fairly quickly and make a decent compost.  You want to be careful with oak leaves however, because they are very acidic and can raise the pH to unacceptable levels.

The use of compost will help build the body or texture of the soil while also increasing trace elements like magnesium or calcium.

Cow/horse manure

Decomposed cow or horse manure has two main benefits. They can act as compost and raise the nitrogen levels.  Manure that is fresher is much higher in nitrogen that will break down as the matter decomposes.

Be very cautious with manure and avoid using fresh unless you are intentionally boosting nitrogen levels for the heavy feeders.  


Lime is an excellent soil conditioner that will help reduce and balance the pH levels. It is simply a ground limestone produce that is available at any hardware store, garden center or supply company.

There is no complex science to applying lime and most often two or three light dusting of the entire garden area will increase pH.

Elemental Sulphur or gypsum

There are situations, although not very often, where the pH of the soil may be too alkaline or sweet and needs to be lowered. The minerals Elemental Sulphur or gypsum will achieve this but beware that there are certain conditions where gypsum is not as effective.

In our experience it isn’t very often that a too alkaline soil conditions exist but there are case where it does so merits at least mentioning.

Bone meal

A calcium deficiency will increase the odds of disease or fungal infestations and this can be remedied using bone meal as a soil conditioner.  Bone is rich in calcium and bone meal is a popular and readily available soil additive that will provide this.

A healthy, rich soil is the core of any successful garden and taking the time to build and improve it before going ahead and planting will yield far better results.  Take the time to develop it before you begin and then continue to sustain healthy soil through good garden maintenance.

Healthy soil just doesn’t produce higher yields, but it also reduces the chance of a devastating disease or fungal infection and results in stronger plants.

It is a win-win all the way around.



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