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All plants have their own specific needs. What these needs are vary from one plant species to another, but all will include varying amounts of nutrients, water and air. Even though water is essential for healthy plants, watering plants too much can be very bad for them.

The focus of this article is water, but this is closely connected to air and nutrients.

The Importance of Aerated Soils

Plants absorb light, carbon dioxide and oxygen through their leaves. But most activity takes place in their roots. Despite the fact that a plant's roots are usually in the soil, one important aspect to this soil (and is often overlooked) is that it contains air. 

Much nutrient absorption in the roots requires energy and this is made available in the roots by the process known as cellular respiration - this requires oxygen. This oxygen is NOT absorbed from the air by the leaves, but is absorbed by the roots from the air spaces in the soil.

Therefore, if there are no airspaces in the soil, then there is limited oxygen available to be absorbed for cellular respiration, and therefore limited energy for the absorption of nutrients.

In fact, limited oxygen in the soil can actually lead to the death of the plant from the roots up - the plant can actually look healthy above the soil but may already be doomed from below the soil.

Soil and Roots

What is the effect of watering your plants too much?

Particularly in poor draining soils, overwatering plants can result in wet, sodden soils. Air spaces in soils that have been overwatered tend to become filled with water instead of air. This results in limited availability of oxygen to the roots and poor nutrient absorption.

When watering your plants, a good rule-of-thumb is to remember that it is best that the soil is moist, not wet.


What is the effect of heavily compacted soils?

Soils that are overly compacted tend to have the air spaces 'squeezed' out of them. This results in significantly reduced oxygen available to the roots. Again, this results in limited energy availability for nutrient uptake.

What is the effect of poorly draining soils?

Heavy clay rich soils are some of the most nutrient rich soils available in the garden, but ironically, they also tend to lock these nutrients up very tightly - while some plants grow well in clay soils, many don't.

The reason for this again comes back to the lack of air spaces in the soil and therefore the relative absence of oxygen available to the roots. This then prevents the absorption of the necessary nutrients in quantities needed by the plant.

Draining Soils

Therefore, to assist with healthy growth, most plants will benefit from you ensuring that there is good oxygen availability in the soil - don't overwater your plants and keep your soil well aerated.

About the author: Steven McLean

I am an educator and passionate gardener and traveler. Throughout my adult life, gardening has been my passion, therapy, drive and source of purpose. Even as a child I had an intrinsic interest in plants and a desire to understand what makes them grow.

I distinctly remember the moment this began - my family was on one of our regular road trips from Hervey Bay; Australia. We were driving past a field of sugar cane. Dad pulled the car over and we cut a couple of sugar cane stems and brought them home for a treat. To be honest, I didn’t really like the taste, but I did want to try and grow it; and that is exactly what I did. It was then that my fascination, interest and passion for gardening and understanding plants began.

Fast forward a few years and I studied biological sciences and began what would be a 36 year career as a Biology educator. From this, I don’t only love gardening, but I also love helping others learn about gardening. I am also always looking for new ways to develop my own gardening knowledge. I like to think I am truly a life-long learner.

Fundamental to my beliefs about education is that learning is often best done as a part of a community - learning from others, and helping others to learn. It is this type of community that I hope iCultivate will be for its members - a community of gardeners, keen to share their gardening knowledge and wanting to learn about new ways to garden - a community built on the love of gardening.

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