Tuesday, November 22, 2011

Soil Myths #5: Do we need to aerate soil?

Have you ever wondered why you might see heaps of holes in the grass at your local park? You may even see the giant tractors rolling across ovals or through parks with heavy metal rollers with spikes all over them making holes all through the grass. This process of hole-making is to help the soil breathe; known as soil aeration. But does soil need this? And do you need to do this with your own lawn or veggie garden?

Why do we aerate soil?  
Aeration, or pockets of air in the soil, is important for drainage and soil health (biology and nutrient cycling) and root space and plant growth. Mechanical aeration of soil is often used on turf to help with drainage and limiting compaction or to improve plant growth in pasture and other environments (see diagram below).

It is the structure of the soil that counts!
The structure of the soil is what affects aeration. Structure is determined by soil biology, organics, salts and clay, sand, gravel and silt. Healthy soil, with plenty of biology and organics, will be able to make its own pores and breathe itself. Soil that is compacted, has poor soil biology and organics will have less pores, and thus will find it harder to breathe itself.

Is physical aeration of soil really necessary? 
Aeration of the soil might be done with tractors and spikes , through manual turning of vegetable gardens (see other Soil Myth), pitchforks, aeration boots etc. However, the weight of the machine in combination with the pressure of forcing holes into soil could possibly create compaction and disturbance. The disturbance can result in poorer conditions for soil biology and exposure of soil to the elements, and the increased compaction can lead to blocking of soil pores, and overall reducing aeration.

But, with really compacted and manicured lawn (turf, cricket pitches, heavily used parks, and playing fields), it may be essential to mechanically aerate the soil. When soil is as compacted as it needs to be in these places, it is hard for roots and biology to live and create good soil structure. In this case, physically aerating the soil might be helpful. The alternative may be no air or drainage, and flooding of fields.

Gardens, house lawns and veggie patches may be a different matter. As long as we look after our soil, it can take care of itself. Just make sure it has plenty of nutrients and organic matter*, and you will be rewarded with well structured, self-aerating soil!

For more information on mechanical aeration of soil, you can try this search on Google Scholar. Or if you are interested in maintaining natural aeration of soil, try this search.

*Tip - If you want a self-aerating lawn, try adding a good broad-spectrum fertiliser. This will help your soil biology flourish, your soil carbon increase and your structure to improve!

Tuesday, November 8, 2011

New Soil Videos!

After my recent (brief) post on environmental videos, I have been alerted to the Soil Science Society of Americas 'The Story of Soil'.

Very much looking forward to checking out these videos when I have a bit more time. They look pretty rad!