What do you know about your soil?
Jan 08, 2025 Posted by Sarah Morrall

Soil is underrated, it is one of the key pillars of human existence. Without it much of our food, clothing, and housing materials would not exist. While we use it productively do we really know much about it?
Hi there, I'm Sarah here from Delmade. If we haven’t met before, let me quickly introduce myself. I juggle a few roles at Delmade, working in Sales and Marketing while also managing farm life and chipping away at an Ag Science degree. (Spare time? What’s that?)
I grew up on a farm, so I know firsthand the challenges farmers face. I’ve spent years on the Delmade sales team, helping match farmers with the right machinery for their needs. With my background and ongoing studies, I’m constantly expanding my knowledge to better support our customers.
In this blog, I will be digging into the dirt on soils. What the different types are and their key characteristics, because knowing your soil's strengths and weaknesses can help you manage it better and make the most of its productivity.
Types & Particle size
So firstly, let’s talk about particles when we look at soil the size of the particles plays a role in many different factors of our soil. Such as how much nutrient it can hold and how much water and air can move through it, which can either be a help or a hindrance. In terms of particle size clay is the smallest, its tiny particles make it great at holding water and nutrients as it has lots of surface area and Negative exchange sites for these nutrients and water to cling to, but this can also lead to compaction as all of these small particles can easily push closer together under pressure, meaning that water and air are displaced.
Silt is the next in line for particle size, silts can be highly productive because again their small particle size allows them to hold onto nutrients, but compaction and erosion (especially from water) can be a challenge.
The final particle type is sand, the largest of the 3 particles, it doesn’t hold onto water as well, most sandy soils are free draining, due to being larger particles they also have fewer cation exchange sites, meaning that they not only allow water to move away freely they allow the precious nutrients to do the same.
After the 3 particle types we get into the blends such as loam soil, which is identified as a mix of both sand and silt particles, it's often considered a favourable soil as it has the benefits of both soil types, nutrient and water holding capacity of silt and the aeration of the sand. Blends come in many different compositions, sandy clay, sandy clay loam and so on (Refer to Figure 2) in these situations the particle that dominates the profile is listed first and then the particles making up the lesser content are listed next. In these situations, the productivity of the soils is determined largely by the dominant soil type.
Figure 1.
Credits: www.support.rainmachine.com
Figure 2.
Credits: www.agric.wa.gov.au
Water Holding Capacity & Infiltration
The particle size of soils affects the water infiltration and holding capacity, larger particles like sand allow the water to infiltrate quickly but also disperse quickly. Whereas clay soils take longer for the water to infiltrate, however, once they are wet they stay that way for longer. Knowing your soil's water holding capacity is important in terms of scheduling irrigation and when it comes to cultivation and crop preparation. When working ground for renovation sandy soil will lose moisture quickly leaving it prone to wind and water erosion. So it's important to consider your soil type when choosing when and how to cultivate.
A portion of the water within the soil will always be unavailable to plants as it is tightly bound to soil particles however, different soil types also have differing amounts of water that are available to plants. The chart below explains the approximate amount of water (mm) available to plants per metre of soil. So when you are considering the type of crops to plant it's important to consider the root depth and the likelihood that you will have sufficient water available to support its growth. To read more about water availability and irrigation scheduling click here.
Figure 3.
Credits: www.nre.tas.gov.au
Nutrients & Cation Exchange Capacity
Once again, the nutrient holding capacity of your soil is highly affected by soil and particle type. The first thing I’m going to go over is the chemistry (hang in there it’s not that complex) so things like clay particles and organic matter have a large number of negatively charged exchange sites on their surface, meaning that cations such as some of our key nutrients are able to form a bond with them where a negative ion such as OH- can bond with a positive ion Ca2+, Mg2+, K+ and Na+ allowing these nutrients to be more available to plants. Whilst sandy soils do have a lower CEC naturally, they can still be fertile, adding fertiliser etc can support healthy crop growth and adding lime or organic matter to the soil will increase the soil's CEC meaning that the fertiliser you add is better retained and more available to plants. Another benefit of the clay and organic matter is their ability to buffer against acidity. Often our base cations (Ca2+, Mg2+, Na+ K+) are easily displaced by H+ Al3+ and Mn2+ decreasing the pH of the soil and causing it to be more acidic and less fertile.
Figure 4.
Credits: www.soilqualityknowledgebase.org.au
You’re probably thinking goodness!! she’s all doom and gloom I promise I’m not trying to panic you into thinking your soils are no good! It's just a matter of giving you the tools to know how to best manage your soil for the best outcomes with the lowest inputs. Now if you are not sure about the type of soil you have there are a host of different resources available to define it for yourself. Texturing is a great place to start, you will find information on how to do it on pages 11-15 of this document "A simple guide for describing soils.pdf" or google "soil texturing" to find a resource that works for you or you can get some professional soil testing done where all of the information is provided to get you started.
Understanding your soil is essential for unlocking its full potential and managing it effectively. Each soil type has unique characteristics that influence its water-holding capacity, nutrient availability, and overall productivity. By learning about the strengths and weaknesses of your soil, you can make informed decisions about cultivation, irrigation, and crop selection, ultimately maximizing returns while minimising inputs.
Whether through simple soil texture tests or more comprehensive soil testing, gaining insight into your soil’s composition and chemistry is an invaluable step toward better management. With the resources shared here, you have the tools to start exploring and optimizing your soil. After all, healthy soil is the foundation of sustainable farming and successful harvests.
Credits:
- Nutrient Management in Tasmania (Bill Cotching) - https://nutrientmanagementtasfarming.com.au/
- Soil Health Tasmania – (click the link and hit download to download the digital book) https://figshare.utas.edu.au/articles/book/Soil_health_for_farming_in_Tasmania/23247812
- Soil Quality Knowledge - https://soilqualityknowledgebase.org.au/