Are we overfertilizing our plants?

[63pmp]

This is taken from a paper presented to the Plant Propagators Society in 1960 by Dr James Kelley, Dept of Horticulture, Kentucky University.


SUMMARY
In summarizing, I would like to say that overfertilization of woody
ornamental can result in a reduction of growth, chlorosis, severe stunting
or death. The symptoms of slight or moderate overfertilization is
a reduction in growth with no unusual leaf characteristics. More severe
overfertilization can cause such symptoms as chlorosis or yellowing of
the foliage, wilting of the foliage, burning of the tips and margins of
the leaf and even death of the plant. Severe overfertilization is probably
not too common. Slight overfertilization is believed to be rather
common. The best method of preventing overfertilization is to use a
sound fertilization program combined with periodic soil testing for
nitrogen and potassium as well as testing for soluble salts by usmg a
solu-bridge. Soil nitrates should be maintained at not over 100 parts
per million and soil potassium levels should not be greater than 300
parts per million on a soil basis. Tentative results indicate that the
solu-bridge reading of a 1:2 soil: water extract should be between 50
and 125 for the woody plants studied. In the work being reported, these
levels were most nearly maintained by fertilizing with a dilute fertilizer
solution containing 1.5 to 2 pounds of 20-O-10 or a 20-o-20 water soluble
fertilizer per 100 gallons of water and applying 1 pint per gallon container
every 10 days throughout the growing season.

values for conductivity are mhos/cm x10>-5

[Jamie]

its funny you bring this up paul as we just had a rather large thread of underfertilizing our trees ?

i wil try and find the thread and link it.

jamie

[Jamie]

here we go

viewtopic.php?f=12&t=3156


it is interesting to think about it though, i mean the thing is aswell, that paper was written in 1960 and a lot of experiments have been held since then

jamie

[anttal63]

things have come a long way since 1960

[63pmp]

Yep, saw that topic, 4 pages of chatter and not one reference to dangerous levels of fertilizer. This paper may be nearly 50 years old, but it is still very relevant to potted culture, and provides more information in one paragraph than in four pages of discussion.


Paul

[Jamie]

yes that may be true as to no discussion of dangerous levels of fert, but since then i have been increasing my ferts and it hasnt harmed the tree since.

not arguing just trying to spur some discussion on it, because it could be the case, but i beleive we are actually under fertilizing and not over fertilizing here in australia, that is reference from a USA paper aswell, if anyone knows about the fertilising of bonsai it would be those that have refined the art over many, many generations, the japanese and chinese for instance, look at how much they fertilise? ill effects? or glorious trees?


jamie

[bonscythe]

Good points 63pmp, I guess I have always been careful of overfert. in potted plants and haven't had any problems. Been mixing to the recommended dilutions/rates and using at the recommended intervals, has worked really well so far. There is a fair bit of info around about ferts and most say to not fertilize if the plant shows signs of stress, which may or may not be due to what that original article was getting at. If you don't fertilize again till the plant regains health/vigour then I reckon your pretty safe from avoiding the problems outlined in the article. I for one wouldn't be giving the plant anything except water and maybe some weak seasol if it's looking crook. But as I said, I guess I have just been (over)careful of this sort of thing?

Edit - Forgot to add that it could also depend on the type of substrate your growing in. I get the impression that rich-organic soils with extra fert would pose more of a risk than those using highly inorganic mixes with the same amount of ferts?

[Greth]

I would say a bit over cautious, bonscythe.
In the 1960's they were probably using a lot of inorganic ferts, which are pretty strong and can cause burning, etc. The slow release stuff was developed to avoid this kind of problem, and the Dynamic Lifter type is aged chook manure, probably safe even if you grew the plant in it pure.
I'm cautious too, and one reason is that I cannot always water reliably, burning problems can be worse if the soil starts to dry out and the mineral salts in the fertilizer become too concentrated, better to go gently if they aren't kept moist all the time, I think.

[bonscythe]

Yeah, I'm leaning toward over cautious too, been amping it up a little week by week!
If your using higher than the recommended dose and the plant starts looking sick, it would only be common sense to lower the dosage right?

[Jamie]

Yeah, I'm leaning toward over cautious too, been amping it up a little week by week!
If your using higher than the recommended dose and the plant starts looking sick, it would only be common sense to lower the dosage right?

thats right mate, so far with where i am at with fert it hasnt had any adverse effects and my fert regime is quite high compared to others but i still just use the reccomended dilutions for liquid.
but i am using a fair amount of it, miracle gro every 7 days, fish emulsion every 10 or so, seasol fortnightly (not a fert but it helps) slow release and now dynamic lifter or the likes.


jamie

[anttal63]

I would say a bit over cautious, bonscythe.
In the 1960's they were probably using a lot of inorganic ferts, which are pretty strong and can cause burning, etc. The slow release stuff was developed to avoid this kind of problem, and the Dynamic Lifter type is aged chook manure, probably safe even if you grew the plant in it pure.
I'm cautious too, and one reason is that I cannot always water reliably, burning problems can be worse if the soil starts to dry out and the mineral salts in the fertilizer become too concentrated, better to go gently if they aren't kept moist all the time, I think.

yep and probably any soil in pots that clogged and held salts and toxins, which also led to over watering. at the end of the day let the tree do the talking. mine are booming growth

[Jamie]

and how much do you feed antonio?

jamie

[anttal63]

and how much do you feed antonio?

jamie

more than you on a weekly basis.

[Jamie]

sounds like i can lift it up a notch then


nice.....


jamie

[anttal63]

there are many factors that allow you to super feed i believe. the only study i have done is to watch my trees. so no fancy jargen here. picking cooler days is one, wetting trees and soil b4 and after a big dose is another. super free draining soil mixes is one of the most important. i cant stress that enough.i know when my trees are asking and i also acknowledge their thankyou.