Watering - the Ideal Soil Water Relationship

| 6/9/2013 10:31:23 AM

Tags: Pore space, Critical watering periods, Too much water, Too little water, Soil water holding capacity, Karen Newcomb,

 Watering—The Ideal Soil/Water Relationship  

Water is an essential ingredient in all plant growth, for almost every botanical process takes place in its presence.  Water is necessary in plants’ food-manufacturing process (photosynthesis), is the main constituent of living cells, and abounds in young plant tissues.  It keeps stems and leaves stiff.  And water is the main ingredient in most of the vegetables we eat, comprising, for example, 91 percent of asparagus, 87 percent of beets, 95 percent of cucumbers, and 94 percent of tomatoes.

You might think that all you have to do in order to grow sumptuous vegetables is pour on the water.  Unfortunately, Mother Nature doesn’t work that way.  Too much water is just as harmful as too little.

Water in the soil carries dissolved nutrients that are absorbed by plants’ roots.  Soil air provides a constant supply of oxygen while carrying off carbon dioxide.  An ideal soil for plant growth generally contains 50 percent solid matter and 50 percent pore space (the space that allows absorption of liquid).  Moisture should occupy about half of the pore space. 

When you swamp the pore space (complete fullness is called field capacity), you cut off the oxygen supply and stop root growth.  The longer the air is blocked, the greater the damage.  Once the roots are damaged, organisms that cause rot enter; root rot frequently sets in.

When you water so much and/or so often that you keep more than 50 percent of the pore space filled yet don’t keep the soil quite saturated enough to cut off the plant’s oxygen, you generally create lush leaf growth at the expense of fruit development.  This happens to tomatoes, eggplant, and peppers that are only slightly overwater.  The symptoms are lots of green leaves but little fruit.

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