Should you always water soil before fertilizing?

coh

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Again, Sandy...you can get chemical (powder or liquid) fertilizers that are urea-free. You don't have to go organic. I'm not saying that you shouldn't, just putting it out there.

Regarding the topic in this thread...the suggestion posted by Markyscott is an interesting way of looking at it. I would imagine their testing was based on soil (peat) type potting mixes? So may not translate perfectly to a completely inorganic soil. Regardless, we have another situation where people are doing it both ways and no one seems to have any complaints. Which means that it probably doesn't really matter. I would still think, though, that if your tree and soil are on the dry side, there is some potential for excessive fertilizer uptake. How dry is too dry, I don't know.
 

Paradox

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I'm less worried about excessive fertilizer uptake than I am with making sure the soil is wet enough for the tree to get enough moisture before the next watering. With the larger particle, inorganic soil we use, it usually is on the drier side when it is time to water. If the tree dries out too much, it won't matter how much or when you applied the fertilizer.
 

Ayxowpat

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From the other side of view... If I water first, the soil particles (granules) are saturated by water. Then after watering with fert, how much fertilizer can be held in the soil and be stored for the tree? Just asking, I use organic fert and liquid inorganic only once a month or so...
Fertilizers are attached to the soil particles like magnets attached to the soil. It is about electrical charge between ions, not about saturation. This also means the cation exchange capacity (CEC).
 

petegreg

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Fertilizers are attached to the soil particles like magnets attached to the soil. It is about electrical charge between ions, not about saturation. This also means the cation exchange capacity (CEC).
If so then it makes a big difference, thank you for explaining it.
 

Forsoothe!

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I fertilize when the soil is damp so I can gauge the volume of liquid fertilizer going into the pot. When the soil is dry it takes up additional water slower and you have to pour, stop, pour, stop. When damp, you pour until the surface is glossy and are more sure about how much it took to get there.
 

penumbra

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I use rather weak solutions but I do it just about every week, and I almost never pre-water.
 

Michael P

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The original reason for watering before fertilizing has to do with using concentrated highly soluble fertilizers. The compounds that plant roots absorb are salts. If the plant is dry and concentrated salts are added to the soil, osmotic pressure can draw water out of the roots even though the soil is wet with fertilizer solution. This desiccates the roots, damaging them and possibly the rest of the plant.

The classic example is applying highly concentrated highly soluble fertilizer to a dry lawn. The lawn is "burned" because osmotic pressure pulls water out of the roots. Of course we don't see this until the leaves wilt or die. You can kill a whole yard this way. Such fertilizers are always labeled with a caution to "water well after application". "Slow release" or organic fertilizers are much less dangerous because the fertilizer salts are released more slowly.

Obviously conditions in a bonsai pot are very different than a lawn. But I still water thoroughly before I use a concentrated soluble fertilizer (Miracle Grow). If diluting the fertilizer well below the recommended concentration, I don't worry as much. And when using slow release artificial fertilizers (Osmocote) or organic fertilizers, I just water on my normal schedule.
 
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