Fertilizer question

[dtreesj]

Say I have a 7 9 5 fertilizer, if I use twice as much, is that like using a 14 18 10 fertilizer?
I have a liquid fertilizer with instructions that call for using twice as much for plant growth, as opposed to just maintenance feeding.

 

[JackHammer]

I don't know much about fertilizer so I am watching here... my liquid miracle grow has directions for every-watering amounts and then every 2-4-week amounts. The 2-4 week amounts are higher (naturally).

 

[cmeg1]

Say I have a 7 9 5 fertilizer, if I use twice as much, is that like using a 14 18 10 fertilizer?
I have a liquid fertilizer with instructions that call for using twice as much for plant growth, as opposed to just maintenance feeding.

Just follow instructions

 

[cmeg1]

Also the dyna gro will work much better after you ph the nutrient when done mixing……..by leaps and bounds.
If stony bonsai substrate ….between 5.5-6.5

I would use less since probably hard water.
Plants will thank you.

 

[dtreesj]

I looked around and found the answer is probably "yes" if it's a water soluble fertilizer that you mix up, but "no" for fertilizers that you apply directly. The NPK is the percentage of the molecule by weight, so if you use the same amount of water but double the fertilizer, you're basically doubling the percentage, but if it's a dry fertilizer and you double it, the weight also doubles so it's still the same ratio, just more of it.

 

[Shibui]

Just be aware that too much of a good thing can be dangerous. It is possible for trees to overdose on some nutrients so best to stay with the recommendations unless you are prepared for disaster or really know what you are doing. most fert rates are conservative to allow for unknown nutrient levels that may be in potting soil and because the companies know some fools will think more is better.
Usually find that high analysis fert recommended mixing is more water to bring it down to safe levels so what you are applying is the same whether NPK is low or high numbers. Higher numbers just means more nutrients, less 'filler' in the bag and it lasts longer before you have to restock.

 

[dtreesj]

Just be aware that too much of a good thing can be dangerous. It is possible for trees to overdose on some nutrients so best to stay with the recommendations unless you are prepared for disaster or really know what you are doing. most fert rates are conservative to allow for unknown nutrient levels that may be in potting soil and because the companies know some fools will think more is better.
Usually find that high analysis fert recommended mixing is more water to bring it down to safe levels so what you are applying is the same whether NPK is low or high numbers. Higher numbers just means more nutrients, less 'filler' in the bag and it lasts longer before you have to restock.

Yup, I just want to understand what's going on. It doesn't make a lot of sense to print the NPK on the front of the bottle and then the back of the bottle gives two different instructions that could change the NPK value to something that you don't know. Not knowing defeats the purpose of having the number on the front.

 

[Shibui]

It doesn't make a lot of sense to print the NPK on the front of the bottle and then the back of the bottle gives two different instructions that could change the NPK value to something that you don't know. Not knowing defeats the purpose of having the number on the front.

I don't follow?
NPK gives you info about RELATIVE amounts of each nutrient. Also allows you to calculate best value for money against other formulations.
Different mixing strengths are for different growth patterns of different species or at different time of life. Changing the mixing ratio does not change the relative balance of the nutrients, just gives the plant more of the same if it needs more nutrient to grow more or faster.

 

[dtreesj]

I don't follow?
NPK gives you info about RELATIVE amounts of each nutrient. Also allows you to calculate best value for money against other formulations.
Different mixing strengths are for different growth patterns of different species or at different time of life. Changing the mixing ratio does not change the relative balance of the nutrients, just gives the plant more of the same if it needs more nutrient to grow more or faster.

Right, it doesn't change the balance but it changes the amount. As you said before, you can give a plant too much, so the amount is something relevant. You could pour the bottle straight in full strength and it would have the same balance, and likely kill the plant, so understanding dilution seems pretty important.

 

[Wires_Guy_wires]

Say I have a 7 9 5 fertilizer, if I use twice as much, is that like using a 14 18 10 fertilizer?
I have a liquid fertilizer with instructions that call for using twice as much for plant growth, as opposed to just maintenance feeding.

Look at it like you would look at sugar cubes.
7 cubes of table sugar, 9 cubes of brown sugar, 5 cubes of corn syrup. Put them all in one cup, you now have a regular concentration.
If you put twice as much cubes in one cup, it'll double the concentration*.
If you prepare two cups with the original 7-9-5 recipe, you'll have two cups at the regular concentration.

*Of course, if you add 21 sugar cubes weighing one gram each, to a 100 gram cup of water, you'll end up with 121 grams. This means your water concentration in total is 100/121*100%=82.64% and your sugar concentration is 100-82.64=17.36%. And if you'd double the amount of cubes you'd have 42 grams of sugar in 100 grams of water, giving you 142 grams in total. This means your water concentration in total is 100/142*100%=70.42 and your sugar concentration is 100-70.42= 29.58%.. Which isn't actually 2 x 17.36 but it's "close enough" for most nutrient solutions.

In more plain language: add one cup of fertilizer to one cup of water, and you'll have two cups of fluid in total. Add two cups of fertilizer to one cup of water, and you'll have three cups of fluid, but not exactly double the concentration because there's simply just more fluid.

Here in Europe, NPK values are based on percentual weight of the entire nutrient molecule calculated from the weight of the total solution.
Since the US uses entirely different standards that don't make sense to me at all, I can't really say how the math works because that too doesn't make sense to me.

I do however recommend to feed more often instead of higher dosages. A steady supply of regular doses is less harmful than a shock approach of high dosage.