Soils are our most important resource, a reality that is rising in prominence as the world seeks to feed its fast-growing population.

So, here comes a fundamental point – without soils, there would be neither farming nor food production taking place anywhere in the world. Understanding the core functionality of our soils is key to managing them on a sustainable basis.

The coming weeks will see the Tillage Edge podcast being dedicated to a series of discussions on how soils can be put to best use on a long-term basis.


The series kicked-off with perspectives given by Prof. Mike McLaughlin – originally from Co. Antrim – but now working as a research professor at the University of Adelaide in Australia.

He explained that clay, silt, sand and organic matter are the solid components of soil.

“Clays are important because they have a lot of the nutrient holding and water capacity within any soil,” he explained.

“Similarly, the organic fraction within soil contains high levels of nutrients.

“It’s the interaction of clay with the sand, silt and organic fractions that determines the fertility of soil in both a physical and chemical sense.”

According to McLaughlin, if any of these components are taken away, problems will follow in terms of agricultural production.

“It really is a team activity in soils,” he said.

“Clays are critical; they are very small particles, which means they have a very large surface area and charge. This helps to maintain nutrients within soils and prevent leaching.”

Organic matter

The organic matter in soils comes from the original vegetation that was on the land.

“We also add organic matter to soils. When a crop is grown, up to 50% of the associated carbon is found below ground,” McLaughlin said.

“In the case of 12t/ha wheat crop with its associated straw, there is in the region of 12t to 15t of carbon biomass growing below ground as well. There is a huge throughput of carbon within agricultural systems that we forget about.”

McLaughlin went on to point out that agricultural production systems actively put carbon into soils.

“It’s the tillage-related operations that we have to be careful about as these activities tend to mineralise the organic matter,” he further explained.

Turning to the issue of pH, McLaughlin stressed that alkalinity or acidity is the master variable within soils.

“This factor alone controls the availability of so many nutrients for crop growth,” he commented. “Soil pH also controls the activity of microorganisms in soil.”