I love hearing from people who want to learn more about their soil! After all, soil is one of my favourite things. I get all sorts of questions from people that call me about their soil. Is it healthy? Does it have a healthy active ecosystem living in it? How can I make it more productive for plants? How can I grow more? Does it have lots of carbon? What do I do about this erosion?
There are so many different ways we can answer these questions, and any questions about soil. Here are some of my top tips!
What is the purpose of understanding your soil?
Before getting stuck into learning about soil, constraining why you want to know more about your soil will help focus on what you need to know. For example, if you want to understand your soil for growing plants, then you need to understand aspects of the soil that are important for plant life, such as soil pH, nutrients, salts, organic matter, biology and soil structure. However, if you want to understand soil because you have an erosion problem, then the soils structural stability, organic matter content and salts are more important. Once you have an aim for understanding your soil, then you can work out what you need to understand. Soil science is a truly vast area of study and knowing your purpose for understanding soil will save a you time.
Do some local research!
I love using local available research for understanding local soils before I go out to site. Resources may include websites that have mapped soils across Australia or in your State (i.e. NSW eSPADE), or it might be other local research and resources from a Landcare group (i.e. soil moisture probes). The local library and maps of metal deposits in your area can also be a great source of information. Other great soil resource websites include State agricultural departments (i.e. Western Australia), Soils for Life and Soil Science Australia.
It is always a good idea to check your local environmental authority to see if there may be any issues associated with contamination of your soil. If you are growing food, it is important to consider possible contamination in your soil and to get it tested. Macquarie Uni offers the VegeSafe service, where you can get rapid testing of soil for some heavy metals for cost of postage and a donation.
If you have any concerns about contamination of soil, always seek expert advice.
Test soil yourself
Two of my favourite tests that ANYONE can do are pH and aggregate stability.
The pH of the soil, that is how acidic (hydrogen ions) and basic (hydroxide ions) the soil may be, is important for nutrients in soil and plant growth. If soils are too acidic or too basic, nutrients in the soil may not be available for plant growth. It is important to recognise that native Australian plants are adapted to a wide range of soil pH, with many of our soils are naturally acidic or basic. This is in comparison to food crops from traditional European cultivars that may prefer a more neutral pH of around 6.5 to 7.5. Anyone can purchase and use a soil pH test kit, and you can find some for sale online, and in hardware and gardening stores. This test can be used to help identify possible soil constraints for plant growth.
The second test is a modified aggregate stability method. Aggregate stability tells you a lot about whether or not the soil has enough organic matter and the right type of salts to help soil particles bind together. Perhaps counterintuitively, soils that clump together allow for good root growth. Soils that disperse can be very hard and erosive, and difficult for plant roots to penetrate. Soil structure is important for roots and organisms to access soil water, nutrients and air, and for reducing soil loss by wind and water. You can do the aggregate stability method yourself by filling up a container with rainwater or deionised water. If you live somewhere where the tap water has low concentrations of soluble salts then tap water is ok too. You can follow the procedure and photos here. I usually just do the 10 minute and 2 hour test (Steps 1 to 3, then Steps 6 to 8) as a starting point for investigations.
If the soil in your soil aggregate test has not done anything at all at the end of the 2 hours, congratulations!! You most likely have stable soil. This means that the soil should have sufficient organic matter and salts in the right form and concentration for the structure of your soil to be less susceptible to erosion and for good growth of plant roots. I once saw a stable soil release bubbles whilst subject to the soil aggregate test. This was from all the air pores and organisms living in the healthy soil – so amazing!
If your soil has fallen apart or slumped in the water, you probably have low organic matter. Adding organic matter to your soil may help improve this problem.
If your soil has fallen apart and/or the water is milky, you are in trouble. Sorry. This means that you probably have low organic matter and high sodium content in your soil. Management of your soil is essential!
If your soil has any reactions in water or has a pH you were not expecting, it is always good to seek expert advice.
If in doubt, get it tested.
There may be a time you need to get your soil tested or bring in an expert. Perhaps you have worked out why you need to better understand your soil, but you are not sure what you need to know? You are worried about contamination? Your pH is really basic or acidic? Your soil makes water milky? These are all signs you need to chat with an expert and get your soil tested.
Let your local soil expert know what you want to know, what you are doing with the soil and what you might be adding to it, any local information you have found and any tests that you have done yourself. They will be able to help you work out a plan that meets your needs!
You can find a local expert through the Soil Science Society, CEnvP, CPSS or through local agronomists. If they can’t help, hopefully they will point you in the right direction.
If you want to know more about soils and poor plant growth and soil contamination, you can find our blog series on these topics here.