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.
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.
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.
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