The Science and Benefits of Subsoiling
Mar 21, 2024 Posted by Sarah Morrall
Subsoiling – taking the benefits underground.
If you’re reading this article, you probably experiencing one of these common issues:
- Problems with soil compaction and root penetration?
- Water and fertiliser are running off your paddocks rather than into the soil where it needs to be for maximum crop growth and output?
- Is a hardpan in your subsoil preventing good root penetration?
- After years of use, has your soil lost its soil structure?
The good news is that these issues can be addressed and one of the most common tools we find effective in these conditions is a Subsoiler (Deep Ripper).
In this article, we will run through some of the major problems we see in the subsoil and how Subsoiling (Deep Ripping) can increase the productivity of your soil.
At Delmade we manufacture Subsoilers – but so you know this article is written from an agronomic perspective not a sales one. We’re not trying to sell you anything it’s just to give you the information to go away and decide on a course of action that is best for your farm. In fact, depending on your soil conditions, you may decide a Subsoiler is not the best option for your situation.
What are the effects of soil compaction?
There are several different factors that can affect the compaction of both topsoil and subsoils and quite a few of them are unavoidable if you are cropping or renovating pastures regularly so it's great to be aware of them.
When we are constantly removing crops or turning over soils it can lead to a loss of soil structure, causing compaction from traffic and soil settling. Settling in compacted soils means there is less aeration and oxygen able to travel through the soil. Oxygen is crucial in the healthy development of plant root systems and their metabolic processes and without sufficient oxygen plants are unable to metabolise carbohydrates and fix nitrogen effectively resulting in reduced plant growth.
Reducing the soil structure can be demonstrated by stepping out in the field grabbing a handful of soil, wetting it and rolling it into a ball. This essentially reduces the soil structure because you are compressing the oxygen out of it. Once that ball dries the soil will become a lot harder especially so in clay-based soils. So, if you can imagine the tractor has run over the paddocks a few times and you’ve had rain when there hasn’t been much ground cover or worse when the paddock is worked up it has the same effect as you rolling the soil into a ball.
Compacted soil is hard to dig and hard to penetrate even if you are just driving a post or a picket so you can imagine how hard it is for a tiny root to punch through and establish itself. If roots aren’t able to push in it is highly likely that water and fertiliser are going to have the same problem, meaning your crops will be less successful and you will also have less microbial activity under the soil.
In summary in compacted soils you will have less microbial activity and plant roots will have a decreased ability to penetrate the soil and establish.
When we lose soil structure and our soils become compacted, they don’t perform as well. Compacted soils won’t retain water and therefore less water will be available to plants. The smaller plant root systems will also mean that the plant isn’t able to efficiently uptake essential nutrients, water and the oxygen it requires for optimum growth.
When we think of nutrient uptake, we can envisage the plant roots as the straws that drink up the nutrients. Less and shorter straws drink up less nutrients. If over time our plants are only taking the nutrients from the top layer of soil, the soil can become depleted. Loosening the soil in the lower levels allows the roots to penetrate and access the nutrients that have previously been locked up. This allows the upper levels of soil time to recover from nutrient depletion.
Along with the issues that subsoiling addresses below the hard pan or within the soil we can also see benefits from subsoiling above the soil surface. The benefits come namely in the form of reduced erosion and the minimising of water and fertiliser runoff. This works by creating pathways for the water to penetrate avoiding runoff. Subsoiling will also assist in ensuring fertiliser benefits are maximised because they are available within the soil.
So how does Subsoiling (Deep Ripping) benefit soils?
When we use a subsoiler or deep ripper we are aiming to shatter and loosen the hardpan that forms in many soils (particularly clay ones). The hardpan tends to inhibit water and roots from penetrating. Using a subsoiler to penetrate down to over 500mm below the soil surface means that the lower soils are disturbed, and the hard pan is shattered. This allows water and oxygen to penetrate and reduces the soil density.
In wet conditions, subsoiling can be helpful by allowing the water that is trapped above the hardpan to penetrate further into the soil. This means that the topsoil drains and becomes more workable. Many potato growers run subsoilers before or with their rotary hoes to ensure that the soil is loosened to a suitable depth to allow for ideal growing conditions.
Implementing a subsoiler into your farm management plan comes with some pretty clear benefits. But the decision needs to come with careful consideration. It’s important to note that rushing in and subsoiling all of your ground is definitely not a good idea. If we subsoil excessively, in the wrong soil type or at the incorrect time, we can potentially intensify the problems we are seeing within the soil. Causing further compaction or reducing the soil structure. So, it is really important to know your soils and crops or speak with your advisor or agronomist to ensure that subsoiling is right for your situation and to make sure if you do subsoil you’re doing it at the right time.
If you would like any further information on subsoiler units and their features and sizing head over and check out our video content in the learning centre Click Here - Learning Centre or follow the link Click Here - Subsoiler to our subsoiler web page for information and brochures.
[1] https://www.jonathangreen.com/soil-compaction-problems-solutions.html
[2] https://www.dcmakesiteasy.com/what-kind-of-soil-should-i-use-and-whats-the-difference-between-soil-and-dirt/