Effects of Overfeeding

[bonsai barry]

While reading Harry Harrington's book, "Bonsai Inspiratons II" I came across a fact about tree physiology that I had not considered before:

"Roots absorb water by a process known as osmosis, whereby water with a low concentration of minerals and nutrients passes through the root membrane, the 'Endoderm' towards the moisture within the rootsystem and the Stele which has a higher concentration of minerals and nutrients. It should be noted that if the water in the soil has a stronger solution of nutrients than the roots, usually as a result of overfeeding, water will be drawn from the roots back into the soil, depriving the tree of water. This process is known as reverse osmosis."

I knew that there were several reasons not to overfeed a potted tree but this fact I hadn't taken into consideration.

 

[Brent]

It really isn't reverse osmosis because water is still passing through a membrane from the lower concentration side to the higher concentration side. It is the reverse of the usual direction for the plant, and thus it dehydrates the plant. Reverse osmosis is moving water from the HIGHER concentrated side of the membrane to the LOWER concentration side. This requires energy added to the system as in the the pressure added to the membrane in a reverse osmosis filtering system.

If you reach a level of soil solution concentration for this to happen, you are really in trouble. This is a concentration so high that it normally can't be achieved with a liquid fertilizer (although possible), but usually occurs when using a solid fertilizer of various chemical salts. It most most often happens in lawns, where solid fertilizer is spread on the surface, then insufficient water is added. This creates a saturated salt solution in the top layer of soil right at the root level. The grass quickly dehydrates and turns a grayish color.

You can use the osmosis process to correct a mild overfeeding situation by flushing the soil with clean water for a couple hours, to continually remove the excess salt from inside the plant's membranes. This might occur if for example you used twice the amount of solid Miracle Gro in the solution. Over feeding results in very lush dark green growth, large leaves, long internodes and generally soft growth. Some diseases and insects are attracted to these conditions such as aphids. It is mostly the nitrogen that is the culprit in these conditions, but too much P and K can also cause toxic conditions.

Probably more than you wanted to know.

Brent
EvergreenGardenworks

 

[Dav4]

While reading Harry Harrington's book, "Bonsai Inspiratons II" I came across a fact about tree physiology that I had not considered before:

"Roots absorb water by a process known as osmosis, whereby water with a low concentration of minerals and nutrients passes through the root membrane, the 'Endoderm' towards the moisture within the rootsystem and the Stele which has a higher concentration of minerals and nutrients. It should be noted that if the water in the soil has a stronger solution of nutrients than the roots, usually as a result of overfeeding, water will be drawn from the roots back into the soil, depriving the tree of water. This process is known as reverse osmosis."

I knew that there were several reasons not to overfeed a potted tree but this fact I hadn't taken into consideration.

Correct me if I am wrong, but I'm pretty sure this is the scenario brought up in every fertilizer thread, particularly when organics are being compared to chemical ferts like Miracle Gro, known by laymen as ROOT BURN...