For all your gardening and landscaping projects the first step is to have your soil tested. You must know to what extent the soil can sustain the plants you want to grow, and what you can do to expand your choices. Soil fertility, organic matter content, soil type, and the pH level of your soil: all these factors will determine which plants will flourish in your garden.
When to do soil testing
Ideally, you should take your soil sample in either early spring or fall when plants are not actively growing.
- Annual testing - Advisable through the early years of your garden so you can monitor the development of the soil, particularly if soil amendments have been added (compost, lime, fertilizers) or your landscaping plans have changed.
- Biannual testing - Sufficient after a number of years to oversee your garden's progress.
How to collect a sample
You should collect a soil sample from each zone - vegetable garden, lawn, flower bed - because soil requirements are varied. As regards your lawn, ideally you should sample at several locations in a zigzag pattern. Refrain from touching samples with your bare hands.
You will need:
- Small shovel
- Plastic or paper bag
- Permanent marker
- Insert a clean shovel or trowel to the depth of the plant's root zone.
- Lawn: 15 cm
- Vegetable Garden: 20 cm
- Trees and shrubs: 30 cm
- Collect approximately 1 cup (250 ml). For the lawn, collect 5 to 15 samples of a few tablespoons each and mix together.
- Put the samples in a clean plastic container or sample box.
- Sift through the sample to remove all stones, weeds and debris.
- Clearly mark your name plus the date and location of the sample. It is important to indicate the square footage of your lawn, since that will determine quantities of earth, amendments, or fertilizers.
- Place the samples in the refrigerator.
- Take your samples to your local BOTANIX and fill out the form that will accompany your samples to the lab.
The soil analysis lab will do multiple tests in order to determine:
- Particle size;
- pH and buffer pH;
- Nutrient content;
- Magnesium and Calcium levels.
Particle size analysis consists of determining the relative amounts of clay and sand, and the percentage of organic matter. Fertilizers applied to clayish soil (heavy) do not produce the same results as when added to sandy soil (light).
Testing will establish the soil pH, which measures the amount of acidity in the soil. A low pH means that the soil is acidic, whereas a high pH indicates alkaline soil. Plant species vary in their soil pH preference, so it may be necessary to add amendments to your soil depending on what you plan to grow. For example, if the soil is too alkaline, you'll need to lower the pH by adding sulfur, whereas soil that is too acidic will require lime to raise the pH. The buffer pH test performed on acidic soil will determine the amount of lime you need to add.
The assessment of soil nutrients and organic matter will indicate the levels of Nitrogen (N), Phosphorus (P), and Potassium (K). Site specific fertilizer and compost recommendations are provided to ensure optimum plant growth.
Your BOTANIX specialist will be familiar with your area and local needs and is therefore well-placed to advise you. The best solution? Select the appropriate plants for your soil right from the start.
Indicating a deficiency
(on the fertilizer package)
An essential nutrient, nitrogen is necessary in the development of leaves and the exposed parts of plants.
Gives plants their green colour.
Unusual foliage colour.
Build the soil with organic matter.
Use a nitrogen-rich fertilizer.
Phosphorus 2nd number
Essential in maintaining a good root system.
Plays an important role in germination, flowering and fruit bearing.
Use a phosphorus-rich fertilizer
Incorporate bone meal combined with mycorrhizal fungi.
Potassium -3rd number
Improves resistance to disease, insects, and cold.
Enhances the flavour of fruit.
Helps plants absorb other nutritive elements.
Leaf edges are crimped and become brown.
Brown spots appear on foliage.
Use manure or compost.
Contributes to the production of chlorophyll, which is vital to photosynthesis.
Helps plants absorb nitrates.
Strengthens the immune system.
Leaf centers become brown, whereas the edges and veins remain green.
Use organic fertilizers
Check the pH and add lime as needed
Contributes to the healthy root systems of young plants.
Stimulates the forming of plant cells.
Shoots and new leaves are curled.
Plants turn red.
Apply organic fertilizer
Turn organic matter into the soil.
Maintain adequate humidity levels, particularly for container plants.
Check the pH and add lime as needed.
Helps plants to absorb crucial nitrogen.
Necessary to the production of chlorophyll, which is vital to photosynthesis.
Leaf edges become sickly yellow or brown.
Use manure or compost.
Choose plants suited to the soil.