Sand Versus Soil
A run down on Perth’s sandy soils and how you can improve your Landscaping
When digging in your garden, have you ever wondered why your soil looks more like sand?
This is because most gardens within the Perth metro, are situated on deep sandy soils. These soils can leave even the greenest thumbed gardener perplexed, as to why his or her plants just aren’t thriving. Although it is best practice to undertake soil improvements when your plants are first going in, it is never too late to give your plants the best chance of survival, even in a fully established garden. Here are a few pointers, which may help to kick start your soil improvement journey.
Soil pH and why it’s important
An important starting point for improving your soils health, is to determine it’s pH. This indicates the soil acidity, or alkalinity on a scale of 1 to 14. Alkaline soils have a pH of higher than 7 and acidic soils a pH of lower than 7 and Perth’s sandy soil, typically ranges from a pH of 4 to 8.5. You can test the pH of your soil either by using a soil pH test kit, which can be purchased at most garden centres, or if you want to get really scientific, you can also take a soil sample to a local laboratory for testing. Once you have determined your soils pH, you can make a start of establishing the optimum pH level for plants, which is generally within the pH range of 5.5 to 7.5. For acidic soils an application of dolomite lime at 100 grams per metre squared, can be used to increase the soil pH by 1 point. Patience is a must for this type of application, as it can take several months to take effect. In alkaline soils, iron sulphate can be applied to decrease the soils pH level (refer to instructions regarding quantities) and is almost instant, in contrast to the dolomite lime application.
Keeping water and nutrients in your sandy soil
Another common issue with sandy soils is water and nutrient retention. Effectively addressing this, will help to increase the overall health of your plants, decrease the amount of watering required and hinder the harmful effects of excessive nutrients leaching into the groundwater system and fragile ecosystems beyond. Organic materials, fine mineral particles and water absorbent gels, are all great ways to combat poor water and nutrient retention. Organic materials including composts, coco peat and broken down animal manure, are all beneficial soil additives. However, when these types of materials become dry, they may also become water repellent. Plant residues, either dry or green, can also be beneficial, but it is vital that these are well composted prior to application, or your plants may be susceptible to disease. Clay, loam and red mud, also known as finer particles, are also great in boosting water and nutrient retention, with the ideal clay content in soil being 5 to 10 percent.
Why sandy soils seem to repel rather than absorb water
As organic materials decompose they leave a wax like coating on sand, which results in hydrophobic (water repellent) soils. Perth is known to have one of the highest concentrations of hydrophobic soil in the world (lucky us), but rest assured there are ways in which this can be overcome. Enhancing the re-wetting properties of your soil can be achieved by applying a wetting agent (available at your local garden centre) and loam, or clay can also help to address water repellence. While kaolin clay is known to be the most affective of the clays, bentonite clay may also be used. Beneficial bacteria have also been linked to the effective break down of the wax like coating on sandy soils. The bacteria help to break down organic materials, while giving beneficial nutrients back to the soil, however, these do require a moist environment to thrive. Mulching your garden with a coarse bark, or pea straw mulch, will help to protect beneficial bacteria, with the added bonus of lowering the soil temperature and reducing water evaporation.
So that gives you a bit of a rundown of some of the problems you may encounter with your sandy soil. Just remember you aren’t alone and if you are thinking of a landscaping service in Perth, we are always here to help. Why not give us a call and we can discuss how we can help you make your garden come alive!
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