Written By Mike Harrington
For decades, farming has been guided by a chemistry-first mindset. We’ve learned to balance nitrogen, phosphorus, potassium, sulphur, and pH, mostly through calcium, by consulting tables and applying soluble fertilisers to facilitate balance. This system, refined through years of scientific tuning, promises predictable yields. However recent seasons have exposed a troubling truth: inputs don’t always equal the expected output and so there is a very important part of the system that isn’t being managed appropriately. Our current approach treats soil as an inert medium, a passive vessel for nutrients. When something’s missing, we add it. Problem solved… or is it?
I am being a little flippant, but I think we can accept that soluble solutions had a lot of one-sided science behind them developed over many decades, mostly based on the chemistry and physics of soil. I remember once being told, by a renowned person, that organic matter could only ever be improved by small amounts in a lifetime because it was a chemical process only. The last thirty years of my involvement have seen huge changes with advances in the science of biology, now coming to the fore. We have begun to see what is required for soil and farming to function at their most efficient. It is biology that becomes the modulator of nutrient capture, retention, recycling and release to the plant. It always has been but hasn’t been given the importance it deserves.
Soluble fertilisers are often used because the soil isn’t functioning biologically. In compromised soils, chemical inputs become a crutch. This raises the question: have we built a system for fertilisers rather than for soil?
Let’s consider an example using AHDB data headed “Weak association between amount of inorganic N applied and yield”. This shows that our current nitrogen system potentially has some flaws. Under a regenerative system, we are not managing a global approach or a global solution to crops anymore. Each farm, as we can see in the chart has individual highs and lows within what is a complex format of what creates yield. Nitrogen is important. I guess the question is over how nitrogen is supplied or is nitrogen the limiter to yield.
I have highlighted a line running across 10 tonnes per hectare. At one end a farmer has achieved 10 tonnes per hectare with little more than 60 kg nitrogen. If we use the rough estimate that a tonne of grain requires 25kg nitrogen, then this farm requires 250kg per hectare, the 60kg applied to the soil would have been at best 50% efficient so roughly, 220kg must have been supplied from the soil system. That is due to biological efficiency, a product of soil functioning or cycling fertility.
At the other end of the scale, we see another farm applying 270kg nitrogen for the same yield, so using the same rough estimates the soil contribution would be lower at 115kg. My picture on the right of the chart indicates the soil would not be in the best of biological states and so an increased balance of purchased inputs is required. Worse still, one farm applied 275 kg and only yields 6 tonnes. Clearly, nitrogen isn’t the limiting factor—soil function, other components are.
When inputs fail
In the example picture below, we see a compromised soil situation, a difficult silt clay, with low organic matter, having very few inputs over many years. So, effectively, poor biology is dominated by physics and chemistry in the soil. This field has been worked into a dry cloddy state with digestate applied into the soil and MAP drilled down and under the maize seed plus additional liquid nitrogen applied after drilling. It effectively has all the nutrients it requires to grow a big maize crop. The poor strip you see is the maize growing in all this nutrient and is a spray miss from a £14.00 per hectare foliar application. Just by putting nutrients into the soil does not always ensure success. In this case they are not connected to anything, and the clods are not connected to the developing maize root. We have all the ingredients for a cake but no cake. As Joel Williams aptly said, “Farming soil without biology is just geology.”
The field next door has been in a multi-species cover crop for ten months and has come through the worst of the wet winter with the picture being taken in November 2024. It shows what the effect has been on soil crumb structure, porosity and fine rooting. The report alongside shows what the cover crop has managed to extract from the soil in the five months prior to measurement, producing 45 tonnes of above ground biomass and 5.9 tonnes of dry matter. Impressive, in what is a very compromised and difficult soil situation.
The power and influence of bigger cover crops is enormous on soil increased microbiome, structure, and nutrient availability.
| Element | Results | Weight/ha |
|---|---|---|
| Nitrogen (N) | 179 | Kg |
| Sulphur (S) | 167 | Kg |
| Phosphorous (P) | 25.6 | Kg |
| Potassium (K) | 184 | Kg |
| Calcium (Ca) | 126 | Kg |
| Magnesium (Mg) | 11.3 | Kg |
| Sodium (Na) | Not measured | Kg |
| Iron (Fe) | 2.7 | Kg |
| Manganese (Mn) | 246 | g |
| Copper (Cu) | 38.1 | g |
| Zinc (Zn) | 147.8 | g |
| Boron (B) | 184.7 | g |
| Molybdenum (Mo) | 11.7 | g |
| Cobalt (Co) | Not measured | g |
| Iodine | Not measured | g |
| Selenium (Se) | Not measured | g |
The large amount of nutrients extracted from the soil collected just in the top growth shows that if we can connect root systems into soil with increased and developing biology we can access and pull a lot of nutrition from the soil. In addition, it is the roots and the exudates that have promoted biological function and therefore it is the biology that has led to the formation of the crumb structure and porosity. We are beginning to create a type of harmony between the soil and the atmosphere with plants being the facilitator.
Let us compare the two fields side by side, the difficult one had rye after maize and the cover crop field had maize drilled into it. They are still compromised soils but look at the difference between the two and what a difference a change in farming can achieve in a short period of time.
The case for change I think is hugely compelling when we have had two very difficult winters and springs from water-logged situations to periods of drought. Both, hugely damaging to the soil ecosystem and very draining on the organic matter food source that feeds this system. It seems to me capturing or applying carbon materials, creating a soil system that has structure, form, all the complex molecules that create the ability to hold nutrients, release nutrients, managing excess moisture in wet conditions. Also holding and releasing moisture during the driest of conditions can buffer the microbiome and promote wider life to flourish to best effect.
The case for staying with a compromised system reliant on outside inputs to manage weaknesses when recent weather patterns have been degenerating what were already compromised circumstances is difficult to comprehend. Starting new season at best in the same poor state but at worst in one that is far worse is concerning. In difficult situations with low organic matter, tillage will improve things in the short term, but it has the reputation of destroying soil structure, ending up tight again if organic material is not added.
This isn’t just about yield, it’s about resilience. The cover crop field demonstrates how biological processes can restore soil structure, porosity, and nutrient cycling. We are beginning to farm in harmony with nature, rather than in isolation from it.
Biodynamic principles describe this as “growing within the organisation of nature.” It’s a shift from control to collaboration with plants acting as facilitators between soil and atmosphere.
If we continue with compromised systems reliant on external inputs, we’ll start each season in a worse state than the last. Tight soils will need lifting, surfaces will need working, and inputs will keep rising. Once soil degeneration has occurred no system can function well or efficiently.
We must rethink, reimagine, and regenerate. The case for change is not just compelling, it’s urgent.