The Tillage Edge series of podcasts looking at the key properties of soils ended with a discussion on how best to improve soil health.
Prof. Mike McLaughlin, from the University of Adelaide in Australia explained that it is possible to improve soil fertility.
“But it depends on the starting point. Obviously, the addition of nutrients will change the potential for crop production, where a specific soil is concerned,” he said.
“The addition of lime to an acidic soil will change its ability to produce crops. Nutrient availability and root growth are limited because of soil acidity.
“In countries like Australia sodic soils create major challenges for farmers, primarily because they have a very poor structure.
“In these soils, we add gypsum in order to improve their physical quality. Soils that are very deficient in organic matter have both a very poor soil structure, but they are also very low in nutrients,” he added.
Improve soil health
According to McLaughlin, adding organic matter to these soils will improve both structure and fertility.
“This approach will also help develop the aggregate composition of soils, which improves both aeration and water retention capacity,” he said.
“Organic matter also has the ability to hold nutrients against the pressure of leaching.”
In China, human excreta has been added to soil for thousands of years while in Europe, the addition of organic waste to soils has been the norm for centuries. These practices have been undertaken in order to boost crop outputs.
“All of this has changed dramatically over the last century, due to the development of artificial fertilisers,” McLaughlin further explained.
“But there are still fundamentals that must be addressed when it comes to improving soil structure that only the likes of organic matter can change.
“In some parts of England e.g., large quantities of clay were added to soil as a means of improving crop outputs. This is a process called marling. Clay is the most reactive component within a soil.”
McLaughlin explained that it is difficult to change the overall clay content of a soil. It is a case of adding tonnes per hectare.
Where organic matter is concerned, it’s a case of adding large quantities to soils if significant structural change is to be effected.
“Organic matter impacts soil quality at a physical, chemical and biological level. Aggregate stability is a key determinant of soil health. However, this factor is significantly controlled by the organic matter content of a soil,” he stated.