Soil - at the root of every great plant!

Date posted: 24 October 2013

Did you know there are more than one billion organisms in every teaspoon of soil? One mm of soil takes 70 years to form but can also be removed by erosion in less than 70 seconds.

Our blog series so far has focussed on the barley plant, but today we are getting down and dirty and looking at the soil. Associate professor Ann McNeill, a research and teaching academic at the University of Adelaide hopes to shed some light on the importance of soil!

1) Why is the soil important for growing barley? Soil is essential to a barley plant… It helps anchor and support their root system. It provides a source of water and nutrients (such as nitrogen, phosphorus, potassium, calcium, magnesium and sulphur) and it holds air to help the plant from becoming waterlogged. Good soil is simply essential to enable large scale food production.

2) What are the key elements of a good soil? Each and every soil is made up of a combination of inorganic particles (stones, gravel, sand silt of clay), organic matter (dead and decaying leaf and animal tissue), living organisms (nematodes etc) and pore spaces. For a soil to be particularly good – it must have the right pore spacing. Pore spacing enables plant roots to move through and explore downwards in search of nutrients and water; they also allow air circulation and influence a soils water holding capacity. Good organic matter is also essential. It influences the pore spacing of the soil, improves aeration and holds nutrients and minerals for the plant growth and development.

3) What can you do to make your soil more productive?

• Preserve the structure – don’t let the top soil blow away!
• Add nutrients to match the demand of the plants you grow (avoid too much at one time).
• Add and maintain organic matter (absolutely essential!).
• Be kind to the soil and be careful how you disturb it, especially if it is clay rich and very wet).
• Understand what the soil is made up of. If it lacks something like organic matter - add it, or if it has poor chemical properties (such as being too acid or alkaline) check if you can change this or grow suitable plants to tolerate the conditions.

4) What lives amongst the soil? There are all kinds of creatures in soil, both plants and animals, varying in size from wombats to microscopic bacteria. These organisms have many jobs - aerating soil, sticking soil particles together into aggregates, cutting up plant residues/litter into smaller pieces and decomposing these to create humus (very fine organic matter that is nutrient rich). There are good and bad guys living in the soil - some of the bad fungi and bacteria cause root diseases of barley but there are good guys that can feed on the bad guys (nematodes that can eat fungi/bacteria). The soil is a very active little community!

5) Why are soil microbes so important to a crop of barley? At least half of the nutrients in the barley will come from the action of soil microbes - since they are responsible for the essential step of breaking down soil organic matter into nutrients

6) What has been the highlight of your career? A definite highlight occurs each year at the University graduation ceremonies. Here, I get to see the students I have taught receiving their qualification. It is great knowing that I played a small part in helping them on the ladder to a successful career. Another highlight has been the wonderful experiences gained from working in so many different countries on soils in agricultural systems.

You can hear more from Ann Mcneill in the Soil Secrets report on ABC’s Landline.