Vegetables Gardening - Growing Organic Vegetables

I agree that drainage is important and have always wondered how hydroponics works. Can anyone explain that science to me?

(In hydroponics the plant roots are not constantly immersed in water, but are in a "soil" medium that is watered several times per day.  The water contains a very dilute solution of the nutrients.  Jim Kennard)

--- In MittleiderMethodGardening@yahoogroups.com, wrote:
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> Why must we avoid allowing our plants' roots to remain submerged in water - doesn't plant breathing all take place through the stomata on the under-side of the leaves?
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> The answer is no. Although garden plants do respire through their leaves, they also must have "soil air", or they can suffocate and die.
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> The University of Wisconsin Extension Service states it thusly:
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> What causes plants to die in water-soaked soils? Besides the obvious killing of submerged branches and foliage, many plants are intolerant to having their roots submerged for long periods of time. Excessive moisture in the soil causes oxygen levels in the soil to decrease, impeding proper root respiration. As a result, carbon dioxide, methane, hydrogen and nitrogen gas levels around the roots increase sharply, thus, roots can suffocate and die.
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> As I have conducted gardening seminars I often ignore the role leaves play in plants' respiration because of the desire to emphasize the importance of proper soil drainage.
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> Both sources are important. But just because plants do receive air through their leaves don't neglect to provide proper drainage at all times, and never allow standing water to sit on your plants' roots for any extended time.
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> Jim Kennard
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