Watering by "Dunking"?

clrosner

From my own experience, Joanie is right on.... I did notice that you mentioned using garden soil.... That type of fine grained soil should slow the water moving through the soil, which I try to avoid.

As I said I can only speak for myself. I have about forty tropicals, which I water almost every day, keeping the temperatures in the above 70 to 90 degree range. I add 1/4 teaspoon of fertilizer for five days of watering and two days with clear water. The two days of clear water is to flush any salts that might accumulate from the five previous days.

When I water from the top (as Joanie decribed) it takes about four seconds for the water to pour out from the bottom of the pot. Thererfore, in less than 15 minutes all my trees recieve their first watering. I wait a minimum of 15 minutes in between waterings, and then for third time I water once again. This third watering is when I examine my trees to see if there are any problems.

The two main reasons I feel that "dunking" is not a good thing, is number one I have too many trees, and second if there is any bad pathogens or some other "disease", it will end up in the water and there is the possibility of the second or third or all your trees might suck up the disease....

The only time I dunk my trees is when I am repotting. I sprinkle the soil with Roots2 granuales, before placing the tree into the pot. Roots2 is to prevent too much shock to the tree. After the completion of the repotting, wiring my tree into the pot, and settling the soil by the chop stick method, I then soak my tree for a half hour. To make sure the soil is totally wet I spray the top surface of the soil with water, and then fill the sink or tub with water up to the rim.

Now you see what you all started? I'm running off at the keyboard!!!

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Brent

You need to know a little bit about physical chemistry, but it's simple. The 'salts' that we are concerned about are mostly carbonates, but there are some others as well, and these are what we call SLIGHTLY SOLUBLE. That is, only a very small amount of them will dissolve in water before it is SATURATED with any particular salt, after which no more will dissolve. To dissolve and remove these salts you must continually add more FRESH (or unsaturated) water.

If you 'dunk' them, only a very small amount of water is involved because only the volume of water inside the rootball is in contact with these salts, no matter the volume of water in the soaking tub. The migration of water will be extremely slow to the point of being negligible. When you remove the plant, the excess water drains out without having removed practically anything. Additionally, only one charge of fresh air will be pulled in behind the drain water.

If you water from above, the water continually drains at the bottom after initial saturation as it is added from the top. Each new volume of water dissolves a little more of the slightly soluble salt. Thus, you can remove, or flush, salts from the soil even with water that is not top quality as long as it is not nearly saturated with these salts as it comes from the tap. The higher concentration of salts it contains (TDS or total dissoved salts), the longer you have to water to flush out salts. Additionally, as the water moves through the soil ball, it continually pulls in fresh air behind it which also greatly increases the air exchange for the roots, which will highly oxygenate the soil mix and flush out exchange gases such as carbon dioxide. All this happens because more than ONE pot volume of water is moving through the soil ball. In fact it is many volumes of water.

What dunking is good for is totally saturating the soil (if you leave the pot in it for more then 15 minutes. This means the soil ball gets a full complement of water. The water is in constant contact with the soil and allows it to 'relax' and replace any gas with water. This can only be accomplished in top watering if you repeat the process several times over the course of 15 minutes to an hour depending on the dryness of the soil and the soil composition. Organic soils when dry become harder to rewet when very dry than inorganic soils. This is why you go back and water again, and again. For efficiency purposes, it doesn't really do a lot of good to just stand there and keep pouring water on a dry plant, it just runs through without really wetting the soil. It is much better to water until water drains out the drain holes, water a few other plants, come back and rewater the first one, and repeat this process. It takes about 15 minutes to achieve COMPLETE saturation of most soils that contain organic amendments.

The very BEST way to water, in my opinion, although there are also other dangers and disadvantages, is to water with a mist/spray system that is automated, so that you can deliver a small amount continually over a long period of time, thus saturating the root ball without wasting a lot of water, and additionally, accomplishing this just before the heat of the day. I usually water about 45 minutes to an hour this way.

Brent
EvergreenGardenworks.com
see our blog at http://BonsaiNurseryman.typepad.com

tazzer

When I water my sapplings (no bonsai yet), I do both. I put the pot in water that goes about 1/4 of the way up the pot. At the same time, I pour water onto the top of the soil. I sorta figured that a little water from the top would "condition" the soil to absorb it from the bottom.

Am I getting the best of both methods doing this? Or just wasting time?

zube

No, Tazzer, I would say you are defeating the effect of watering from above by not enabling the water to run through the pot.
zube

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dtree

Thank you, Brent, for your detailed explanation.