Understanding pH and Soil Drainage
Healthy Plants Need Healthy Soil
Growing a healthy plant, starts with healthy soil! Here are a few factors to consider when mixing and maintaining your soil for healthy plants. These will also vary depending on the specific plant and type of garden you are growing, but let’s start with the basics.
pH
pH is the measure of acidity or alkalinity of a substance. It is a scale from 1 to 14. Low numbers are more acidic and high numbers are more alkaline/basic. 7 is the magic number that marks neutrality. Every unit from 7 indicates the soil is 10 times more acidic or basic. pH is important because it changes the chemistry of the soil. If it is too high or low, nutrients can become less available to the plant because of the chemical state. Acidic soils can cause deficiencies of phosphorus, calcium, magnesium, and molybdenum and cause toxic levels of manganese and aluminium. Alkaline soils can cause deficiencies in iron, manganese, boron, copper, and zinc. This means that the pH can directly affect the health of your plant if nutrients are unavailable to them. Many plants perform best in neutral soils (pH approximately 7.0) however some prefer acidic or basic soils.
An example of some common plants and there pH levels can be found below. For a detailed list, please read our Optimum pH for Common Plants article.
| Acidic (pH 4.5 – 6.0) | Basic (7.0 - 8.0) | |
| Ornamental |
Azalea Camellia Erica Gardenia Holly Hydrangea Magnolia Pelargonium Rhododendron |
Sweet Pea Cacti Geranium Gerbera Hebe Hibiscus Ivy Poinsettia Viburnum |
| Fruit |
Blueberries Cranberries |
Melon |
| Vegetable | Potato |
Beetroot Chervil Choisya Leek Spinach |
To measure the pH of soil, use your Carbon Garden 3-in-1 Garden Meter (included with your Carbon Garden Kit), which is super easy to use and gives you a quick reading of the soil pH. If your soil is too acidic, add lime to increase the pH. If your soil is too alkaline, add sulphur to decrease the pH.
Water retention/drainage
Plants require balance between water retention and adequate drainage for optimal health. To find this balance you need to consider watering routines as well as soil drainage. If there is not enough water, the plant cannot grow. If soil is inadequately drained, the water build-up prevents aeration of the soil. This creates an environment where harmful bacteria and fungus can multiply and attack the roots, leading to root rot (a large part of The Carbon Garden program, is all about promoting healthy, good bacteria and fungus, but harmful microbes can cause serious problems if left unattended.) If oxygen is lacking in the soil, there is interference of nutrient uptake into the plant and photosynthesis which creates energy for the plant.
You can use your included 3-in-1 Garden Meter for an easy option to understand whether your plants are ready to be watered or not. Alternatively, you can insert a finger into the soil to test the moisture. It is important to know that different plant types have individual watering requirements, and you should always read their labels for a better understanding of their needs.
Plants show signs as well. Underwatered plants may have brown crispy tips of leaves. Overwatered plants may be wilted despite moist soil, brown limp leaves or yellowing.
| To increase water retention | To increase water drainage |
| Add vermiculite | Add perlite or pumice |
| Add peat moss | Add sand |
| Ensure adequate holes at bottom of pot | |
| Add charcoal | |
| Add layer of gravel at the bottom of your pot |
Nutrients
Soil provides the major source of nutrition for plants. As we have discussed, pH and water retention in the soil play an important role in the availability of nutrients for a plant. The main nutrients required are nitrogen, phosphorus and potassium which together form the trio NPK. Plants also need calcium, magnesium, sulphur, iron, manganese, zinc, copper, boron, and molybdenum.
Humus is nutrient rich and a great way to replenish nutrients in your garden. It is the decomposed product that results from composting. Another natural fertiliser is manure which can be added to your garden. To complement the addition of nutrients, using CropBioLife helps your plant to utilize available nutrients better. It aids uptake of nutrients, transport of nutrients around the plant and utilization of the nutrients.