The Importance of Soil Testing Before Planting Your Garden

When deciding to buy plants for a garden most people envision beautiful plants that flower all year round.

But, wait! Before you spend all your hard-earned money on plants, there are important things you really need to understand. What soil do you have and what plants are best suited to grow in it?

One of the most important steps in growing great trees, shrubs, perennials, vegetables and herbs actually happens before planting: Testing the soil where you will be planting your garden.

The soil is a large part of what makes your plants grow and testing it is a definite must for growing a beautiful garden. Not as much fun as planting and watching the plants develop but imperative to getting the best results.

So, what is soil testing?

Soil can be tested for many things but gardeners usually test the soil’s mineral health and fertility. 

These tests are inexpensive and the best way to gain the knowledge required to make decisions on how to treat the soil and what plants will best grow in it.

Testing can help to improve the enjoyment you can get from your garden and it can save you money too!

That’s right, better plants for less investment. Read on to find out more.

Why is soil testing important?

The best way to answer this question is to go back to the 19th century when the German scientist Justus von Liebig formulated the “Law of the Minimum,” which states that if one of the essential plant nutrients is deficient, plant growth will be poor even when all other essential nutrients are abundant.

How will you know if the soil is deficient in a nutrient if you do not test it?

Planting a garden without first testing the soil is like driving a vehicle while wearing a blindfold. SOIL TESTING IS IMPORTANT!

Questions you should be asking 

All plants need nutrients to develop properly. Many (if not all) of these nutrients will already be available in the soil in your garden, but how do you know if you have too much or too little? 

And what is the PH (acidity or basicity) of the soil? 

How much organic matter is there and do I need to add more? 

All of this information will help you to choose the right plants and the best amendments (compost, conditioners, manures, fertilizers, etc.) for your soil’s condition. 

And ask yourself this: Why waste money adding products you do not actually need?

All the answers are down there in the soil, you just need to look 

The answers to the above questions can be found in a soil test. 

Soil nutrient analysis services come in packages depending on your budget, from basic macronutrient tests to the full-spectrum analysis of the mineral nutrients plants need. All tests tend to include the PH value and some tests can include cation exchange capacity (CEC), soil texture, particle size and organic matter.

Unfortunately, nitrogen samples degenerate quickly and are difficult, (but not impossible,) to test for. Nitrogen is also highly mobile in soil so test results can vary too much to be of any real benefit to a gardener.

Soil nutrients for a healthy garden

You do not have to understand nutrients to get a soil test and read the associated advice but here is the technical stuff for those that are interested.

Non-mineral nutrients make up the vast majority of the plant, (96%). These consist of oxygen, hydrogen and carbon. They are available to plants in air and water so the plant just needs good access to air and water through its leaves and roots to obtain adequate supplies of these essential nutrients.

The other 4% are the mineral nutrients, which may seem like a low amount but they are no less important to plant health.

Mineral nutrients are divided into macronutrients (used in larger quantities) and micronutrients (used in only trace amounts).

The macronutrients obtained in mineral form are: Nitrogen, phosphorus, potassium, calcium, magnesium and sulphur.

The micronutrients obtained from the soil are: Boron, chlorine, copper, iron, manganese, zinc, molybdenum and nickel.

Each nutrient has a different degree of mobility in the plant and in the soil and this affects how they should be treated. Excessive nutrient leaching has a negative impact on the environment so adding excessive amounts of nutrients is not just bad for your wallet.

Soil PH and Soil Structure

Soil pH determines if your soil is acidic or alkaline. Most soils are in between, working toward a neutral point. The pH of the soil largely determines which plants will grow best in your garden.Soil pH is measured on a scale of 1 to 14 with a measurement of 7.0 considered neutral. A number below 7 is acidic (sometimes called “sour”), and a number above 7 is alkaline (“sweet”). Most plants prefer nearly neutral soil in the range between 6.2 and 7.2 although higher and lower values are common and many plants are quite PH tolerant. 

Wide bars indicate higher nutrient availability and narrow bars indicate decreased nutrient availability.
(University of Florida/IFAS Extension,

Soil structure contributes to drainage and the ground “room” available to the plant to develop a good root system. It also contributes to water retention, which is important for a healthy soil ecosystem and reduces the need to water the soil, therefore, less wasted water and leaching of nutrients.

Adding good organic matter is generally good for the ‘soil food web’. Some sources suggest that (ideally) organic matter makes up at least 2 to 3 percent of the soil for growing lawns and 4 percent to 6 percent of the soil for growing beds.

When and How Often Should I Test the Soil?

This can depend on a number of individual circumstances but, as a general guide, you can test any time of the year, then take a second test one year later to see if your actions are working. After that every two or three years will suffice.

Where to get a Soil Test

The RHS offer a Soil Analysis Test:

For a greater choice of tests you can go to Hill Court Farm Laboratories:

The Soil Association can provide more information:

Contact us for complete soil testing service and help with your soil test results, soil conditioning and planting needs.

Leave a Reply

Your email address will not be published. Required fields are marked *