View Full Version : Fertilizers: N-P-K and Quantity
Richard
06-30-2009, 10:17 AM
My impression is that too many people are focused on what formula to use without understanding what quantity to apply.
The N-P-K rating of a fertilizer is percentages, not quantity. Fruiting bananas in the ground or a very large container will utilize up to 1 net pound of nitrogen and 1.5 net pounds of potash per year. Note that the potash can only be utilized to the extent that nitrogen is present.
For fruiting bananas in non-tropical regions, the proportion of 1 part nitrogen (N) to 1.5 parts potash (K) is an excellent ratio. The following fertilizers can all provide it: Alfalfa Meal (2-0-3), Geritz Garden Mix (10-5-15), Scotts Miracle-Gro For Fruits (16-8-24), Grow More 20-5-30.
Getting a good formula is not enough. You also need to compute the amount to use.
Alfalfa Meal 2-0-3: 1-lb Nitrogen divided by 2% ==> 50 lbs per year per plant.
Geritz 10-5-15: 1-lb Nitrogen divided by 10% ==> 10 lbs per year per plant.
Scotts 16-8-24: 1-lb Nitrogen divided by 16% ==> 6.25 lbs per year per plant.
FINALLY I think I get it now.
turtile
06-30-2009, 10:04 PM
FINALLY I think I get it now.
To make it more confusing, P and K aren't really percentages of the element. P is measured as the percentage of P2O5 (around 44% P), and K is K2O (around 83% K). You would have to add more K to the ratios above to really net 1.5lbs of K.
conejov
06-30-2009, 10:06 PM
Interpreter please? Some one have a Dummies to fertilizer ratios guide?...Im sorry but Im alittle slow..
turtile
06-30-2009, 10:11 PM
Interpreter please? Some one have a Dummies to fertilizer ratios guide?...Im sorry but Im alittle slow..
If you buy a 100 pound bag of 10-10-10
10 N = 10 lbs Nitrogen
10 P (P2O5) = 4.4 lbs Phosphorus
10 K (K2O) = 8.3 lbs Potassium
Richard
06-30-2009, 11:40 PM
John,
The ratios I'm referring to are for available nitrogen (N), phosphate (P), and potash (K).
... For fruiting bananas in non-tropical regions, the proportion of 1 part nitrogen (N) to 1.5 parts potash (K) is an excellent ratio. The following fertilizers can all provide it: Alfalfa Meal (2-0-3), Geritz Garden Mix (10-5-15), Scotts Miracle-Gro For Fruits (16-8-24), Grow More 20-5-30.
Getting a good formula is not enough. You also need to compute the amount to use.
Alfalfa Meal 2-0-3: 1-lb Nitrogen divided by 2% ==> 50 lbs per year per plant.
Geritz 10-5-15: 1-lb Nitrogen divided by 10% ==> 10 lbs per year per plant.
Scotts 16-8-24: 1-lb Nitrogen divided by 16% ==> 6.25 lbs per year per plant.
Patty in Wisc
07-01-2009, 01:40 AM
That's OK Alex, I got strait A's in math & science, but I don't understand what these equations are either. They just don't make sense to me.
I use all water soluable stuff, so 50 lbs of anything sounds like a lot to me!
I just put my compost on & fert w/1 Tblsp or 1 tsp. per gal of water depending on which fert I use, & it works fine. Sorry if I'm ignorant Gang!
Richard
07-01-2009, 03:58 AM
That's OK Alex, I got strait A's in math & science, but I don't understand what these equations are either.
These equations are "proportions" which in the U.S. are now taught in 7th grade math. As an example:
Suppose your fertilizer is 15% available nitrogen and you want to know how much will provide 1 net pound of nitrogen. Your equation to solve is:
X * 15% = 1 lb
so
X = 1 lb / 15%
turtile
07-01-2009, 05:26 PM
John,
The ratios I'm referring to are for available nitrogen (N), phosphate (P), and potash (K).
All of the ratios you provided use P2O5 and K2O. Unless you mean that the ratios net 1.5lbs of K2O equivalent and not just K.
chong
07-01-2009, 07:07 PM
John,
The ratios I'm referring to are for available nitrogen (N), phosphate (P), and potash (K).
All of the ratios you provided use P2O5 and K2O. Unless you mean that the ratios net 1.5lbs of K2O equivalent and not just K.
I think that by introducing the issue of the chemical compounds, from where each of the three N-P-K elements are derived, it is just making things more complicated than we need to be. We can probably all agree that those elements, N-P-K, are not in their elemental form, but rather as part of a compound, e.g., NO3, P2O5, K2O, etc. The labeling that we read is mandated by law to reflect the percentage availability of the elements and not the compound that they are part of. If percentage of the compounds were to be listed on the labels, i.e., NO3-P2O5-K2O, they would deviate from the intent of the labeling, which is to confirm the availability of each of the elements N-P-K.
As an example, an N-P-K formula of 10-10-10 might have an equivalent to 16-25-10 for NO3-P2O5-K2O. But if you are calculating the amount of each element you would like to feed your plants, it would be impractical to list the latter. See the link below:
Understanding Fertilizer Numbers: N-P-K (http://www.learn2grow.com/gardeningguides/fertilizer/basics/understandingfertilizernumbers.aspx)
turtile
07-01-2009, 09:01 PM
I think that by introducing the issue of the chemical compounds, from where each of the three N-P-K elements are derived, it is just making things more complicated than we need to be. We can probably all agree that those elements, N-P-K, are not in their elemental form, but rather as part of a compound, e.g., NO3, P2O5, K2O, etc. The labeling that we read is mandated by law to reflect the percentage availability of the elements and not the compound that they are part of. If percentage of the compounds were to be listed on the labels, i.e., NO3-P2O5-K2O, they would deviate from the intent of the labeling, which is to confirm the availability of each of the elements N-P-K.
It doesn't matter which compounds are present in the fertilizer. P and K must be represented as P2O5 and K2O by law. Before modern technology, fertilizer was tested in the oxide form.
If you buy muriate of potash (KCl), the label will read 0-0-60. While the actual K content is more around 50%.
adrift
07-01-2009, 09:19 PM
John,
The ratios I'm referring to are for available nitrogen (N), phosphate (P), and potash (K).
Golly gee, it's easy to see y'all are plant people cause you re-use and mix up the names of everything.
Correctly restating your quote: The ratios I'm referring to are for available nitrogen (N), phosphate (P2O3), and potash [fertilizer](K2O)
P is phosphorus, an element; not phosphate.
K is potassium, an element; not potash.
To keep everyone on their toes...
"Real" potash is a mixture of compounds, mostly K2CO3 = potassium carbonate but also many (MANY) naturally occurring salts of this compound. Probably because this stuff was first used hundreds of years before people knew enough chemistry to figure out what the compounds in their ashes really were.
BUT, there is a chemical called "potash fertilizer" which is potassium oxide K2O, which isn't even used as fertilizer because it is so caustic. But it IS the standard measure of the amount of potash IN fertilizer.
So, in reality the potash fertilizer IN fertilizer is not "potash fertilizer" but some mixture of potassium carbonate, potassium nitrate (salt peter), potassium chloride (muriate of potash; "salt substitute"), potassium sulfate, potassium permanganate, or potassium hydroxide (potassium lye).
Patty in Wisc
07-01-2009, 09:26 PM
Thanks Chong & KJ.
adrift
07-01-2009, 09:29 PM
I think that by introducing the issue of the chemical compounds, from where each of the three N-P-K elements are derived, it is just making things more complicated than we need to be.
Perhaps, but it is what it is.
We can probably all agree that those elements, N-P-K, are not in their elemental form, but rather as part of a compound, e.g., NO3, P2O5, K2O, etc.
True.
The labeling that we read is mandated by law to reflect the percentage availability of the elements and not the compound that they are part of.
False.
While, for simplicity, many people say it is "N-P-K" and imply that it is the pure elements, (and say so on web sites), by government definition it is nitrogen, phosPHATE, and potASH.
Don't go to gardens-R-us.com, look at a university or government site.
adrift
07-01-2009, 09:31 PM
It doesn't matter which compounds are present in the fertilizer. P and K must be represented as P2O5 and K2O by law. Before modern technology, fertilizer was tested in the oxide form.
Bingo!
adrift
07-01-2009, 09:44 PM
Here are your homework problems for tonight. Don't skip #3 or #5 they are informative about labeling.
Practice Problems for Fertilizer Analysis (http://www.public.iastate.edu/~teloynac/354ppfertsol.html)
CValentine
07-01-2009, 11:31 PM
Here are your homework problems for tonight. Don't skip #3 or #5 they are informative about labeling.
Practice Problems for Fertilizer Analysis (http://www.public.iastate.edu/~teloynac/354ppfertsol.html)
WOW!!!
I actually enjoyed working through that!
I have learned something new today, Thank you!! :)~Cheryl
island cassie
07-01-2009, 11:49 PM
Haha! hopefully I won't be tested on that! My excuse is that I can't go with a shopping list and buy anything I need - whatever I see - I buy in case I never see it again - then figure out how to use it. A different slant perhaps?
chong
07-02-2009, 12:39 AM
I think that by introducing the issue of the chemical compounds, from where each of the three N-P-K elements are derived, it is just making things more complicated than we need to be.
Perhaps, but it is what it is.
That opening sentence was the whole purpose for the post. It was an appeal to simplify the discussions in layman’s terms rather than to spark additional motions or arguments that only most people in academia will understand. I do not believe that Richard’s initial post was anywhere near as complicated as this is now turning out to be. If we were to go back to that post, what I think Richard wanted to relay was that if you want to feed a plant a certain amount of nutrient per year, i.e., N, P, or K, all you need to divide the pertinent nutrient by the percentage of the nutrient to arrive at the amount of fertilizer you will need to feed that plant.
We can probably all agree that those elements, N-P-K, are not in their elemental form, but rather as part of a compound, e.g., NO3, P2O5, K2O, etc.
True.
Hold that thought . . .
The labeling that we read is mandated by law to reflect the percentage availability of the elements and not the compound that they are part of.
False.
While, for simplicity, many people say it is "N-P-K" and imply that it is the pure elements, (and say so on web sites), by government definition it is nitrogen, phosPHATE, and potASH.
Don't go to gardens-R-us.com, look at a university or government site.
Indeed you are right. And I will concede that if accuracy is critical, a university or government site would the place to go. But I haven’t found any of those sources that clearly explain these facts to the same detail as you, when applying those formulas for plants. In fact, most of the ones I’ve seen only go so far as the way Richard figured the amounts in his original post.
As I explained in my opening statement, the bottom line is: to what degree do we carry this accuracy? Do we use a scale and weigh the fertilizer every time we fertilize? Or, do we just rely on the label of the product, and then just eyeball the amounts when dividing? And if we have several plants of varying requirements, would we need to meter the amount of fertilizer at each plant and record the number of times that they’ve been watered? Perhaps your point is somewhere in between. If so, why worry about the 10% in N actually amounts to only 8%. I don’t think the plants will know the difference.
I believe that when garden writers give advice, the advice they give will help in almost all cases. If they refer to the percentages in the label as a gage to apply the fertilizer, I believe that in most cases that’s what they use themselves.
I don’t know if anybody else actually figures exactly how much to feed their plant like you. Personally, I just use the formula that Richard listed in his initial post on this thread. There are some active farmers in this forum, and I doubt if any of them do not calculate their needs that same way as Richard.
Richard
07-02-2009, 04:04 AM
Golly gee, it's easy to see y'all are plant people cause you re-use and mix up the names of everything.
You know, that was my thought when I first started reading agricultural extension papers from Cal Poly San Luis Obispo, UC Davis, Yale, and U of Florida. In mathematics, we call it "abuse of notation" when something is abbreviated to the point of ambiguity. The fact is though, that when you read a plant science report recommending N-P-K ratios of 3:1:2 for citrus or 16:1:24 for bananas, they are referring to the N-P-K of fertilizer labels and not the literal meaning of the symbols in chemistry.
turtile
07-02-2009, 06:49 PM
You know, that was my thought when I first started reading agricultural extension papers from Cal Poly San Luis Obispo, UC Davis, Yale, and U of Florida. In mathematics, we call it "abuse of notation" when something is abbreviated to the point of ambiguity. The fact is though, that when you read a plant science report recommending N-P-K ratios of 3:1:2 for citrus or 16:1:24 for bananas, they are referring to the N-P-K of fertilizer labels and not the literal meaning of the symbols in chemistry.
You will not find one report using N-P-K ratios for fertilizer. You'll find N-P2O5-K2O. Look at any fertilizer analysis label and you will not find one that uses N-P-K. There is nothing confusing about it. The labels display the exact percentage of the symbols on the analysis.
If you read report stating the tissue analysis, N-P-K will be used.
Richard
07-02-2009, 10:09 PM
You will not find one report using N-P-K ratios for fertilizer. You'll find N-P2O5-K2O. Look at any fertilizer analysis label and you will not find one that uses N-P-K. There is nothing confusing about it. The labels display the exact percentage of the symbols on the analysis.
If you read report stating the tissue analysis, N-P-K will be used.
I see we are in complete agreement!
turtile
07-02-2009, 11:06 PM
I see we are in complete agreement!
No, elemental P and K don't exist on fertilizer recommendations. The amount of nutrients taken up by a plant are in the elemental form. Thus, you must convert the elemental from into the oxide from in order to add the same amount of elemental nutrients into the soil.
Therefore, the 1.5lbs of elemental potassium that you say a banana takes up must be converted to the oxide from in order to make a fertilizer recommendation.
Fertilizer labels do measure by the chemical symbols stated which is completely opposite from your statement. Again, there is nothing that you can't read on the fertilizer label.
Richard
07-02-2009, 11:33 PM
Therefore, the 1.5lbs of elemental potassium that you say a banana takes up must be converted to the oxide from in order to make a fertilizer recommendation.
Somewhere you have misunderstood. My statements have concerned potash, especially here: Info:Fertilizer - Bananas Wiki (http://www.bananas.org/wiki/Info:Fertilizer)
turtile
07-03-2009, 08:48 PM
Somewhere you have misunderstood. My statements have concerned potash, especially here: Info:Fertilizer - Bananas Wiki (http://www.bananas.org/wiki/Info:Fertilizer)
Your original post stated potassium with the symbol K in parenthesis. K is the symbol for the element potassium which still exists next to potash in your updated post.
N-P-K: The percentages by weight of Nitrogen (N), Phosphate (P), and Potash (K) in a fertilizer. For example, a fertilizer labeled 4-1-1 has 4% N, 1% P, and 1% K by weight. This is true for both liquids and solids. A common beginner's error is attempting to make a custom fertilizer mix by volume instead of weight.
Again, you are using chemical symbols for the elements and are misinterpreting the fertilizer labels. Its not 1% P but P2O5, and not 4% K but K2O by weight.
Minor and Micronutrients: Plant scientists have identified over 20 minerals required by plants for normal growth. The Primary nutrients are N, P, and K. For convience, manufacturers and retailers usually lump the others under the single name 'micronutrients' -- although a plant scientist would label Calcium, Magnesium, Sulfur, and sometimes Iron as 'minors'. It is important for gardeners to understand that there is a complex chemical relationship between all of the mineral nutrients. Too much or too little of one in the growing media can inhibit the plant from uptaking others. This condition can be avoided by choosing products and materials that contain a set of micronutrients that are balanced for plants.
Macronutrients:
- Primary : N, P, K
- Secondary: S, Ca, Mg
Micronutrients
- Mn, Fe, Mo, B, Cl, Na, Zn, Cu
The urban myth is that it comes from urine, but in reality it is most often mined from dry lake beds in deserts.
Urea is synthesized - not mined.
Chelate: Some elements of fertilizers are highly reactive in raw form -- e.g., phosphorus.
Only metallic micronutrients are chelated.
an over-abundance of a mineral nutrient -- the most common two are Sulfur and Chlorine, esp. from murate of potash,
Sulfur toxicity practically does not exist.
Richard
07-03-2009, 09:21 PM
Your original post stated potassium with the symbol K in parenthesis. K is the symbol for the element potassium which still exists next to potash in your updated post.
That's true, it is the standard abuse of notation in agricultural publications and products. I have here a 25-lb bag of water soluble fertilizer: on the cover the ad copy says "... the NPK proportions of 15-5-15 are excellent ..." and on the back the Guaranteed Analysis gets the chemistry correct by listing proportions of N, P205, and K20. I have agricultural extension publications from Cal Poly SLO, UC Davis, and UF which discuss requirements for "phosphate (P)" and "potash (K)". They do this because that is what the intended audience (farmers) will understand.
A long time ago I tried to enforce my ideas of strict adherence to notation in the world of mathematics and physics. I especially became frustrated with the abuse of calories, Calories, c, C, kcal, etc. -- especially in biology and dietary publications. I finally gave it all up with a good laugh when a colleague pointed out to me that in dietary publications:
c = calories at the speed of light
adrift
07-07-2009, 02:12 PM
That opening sentence was the whole purpose for the post. It was an appeal to simplify the discussions in layman’s terms rather than to spark additional motions or arguments that only most people in academia will understand. I do not believe that Richard’s initial post was anywhere near as complicated as this is now turning out to be.
It may not show from the postings, but I really appreciate Richard's work to educate people about what they put (or what they should put) on their plants. He also shows them the cost per effective nutrient so they can see when they have a good deal (or more often, when not). So for that I applaud him.
I agree we need to make things simple for the average consumer. And I think intelligent, rational people can discuss how far something can be simplified before it becomes wrong.
I know that people talk about N-P-K on fertilizer and *I* believe they should know that that is a bit of an *oversimplification*. I think it could be said something like, "What is on the label is nitrogen, phosphate and potash. Because the active part of phosphate is the element phosphorus (chemical symbol P), and the active part of potash is potassium (chemical symbol K), some materials discussing fertilizer call this its N-P-K rating."
Just, please don't say K is potash.
I don’t know if anybody else actually figures exactly how much to feed their plant like you.
Oh, no worries on that. I don't do any math. I throw in whatever much per gallon and give it to the plants every few weeks when I have the time and when I remember. I'm just providing that for the curious. I'm not collecting the homework for a grade. :woohoonaner:
Besides, what is the ideal for any plant to take up can really only apply to hydroponics. Most people have *something* already in their soil. Without a soil analysis, whether it is better to put 10-2-10 or 8-3-18 is speculative. Unless someone is competitively engaged in for profit banana production, it is probably good enough to pick something low in phosphorus and high in potash with a moderate nitrogen rating. Don't worry so much about the last decimal point. Like the old homebrew saying, "relax and have a homebrew."
Richard has told people that (almost) anything is better than nothing. So I think we agree on another point.
adrift
07-07-2009, 02:15 PM
A long time ago I tried to enforce my ideas of strict adherence to notation in the world of mathematics and physics. I especially became frustrated with the abuse of calories, Calories, c, C, kcal, etc. -- especially in biology and dietary publications. I finally gave it all up with a good laugh when a colleague pointed out to me that in dietary publications:
c = calories at the speed of light
When I tell people the square root of -1 is "j" (because "i" is current) they roll their eyes at me.
We must be the life of the parties we attend.
Patty in Wisc
07-07-2009, 09:28 PM
The following is in the wiki. I find it interesting to see what other members are using, and many of them fruited many healthy bunches! I posted then ('06) that I used MG tomato food - 18-18-21 because it was all I could find w/ higher K. I use Banana Fuel now - 15-5-30 w/ all the micro's.
Members Methods
The Flying Dutchman: Dried Cow Manure and once in a week a liquid fertilizer(7+4+6)
MediaHound: I make a compost mixture with surplus material from the kitchen combined with most all organic waste from the yard. I'm now using use three UCT9.5 compost bins. I also use a variety of packaged commercial fertilizer and micronutrients. Seaweed, liquid fish, composted manure, etc. MediaHound 09:46, 24 April 2007 (EDT)
Patty in Wisc: Tomato food 18+18+21 because it has more K.
Pitangadiego: Triple 16 is cheap and effective
Chong: I find that since bananas are heavy Potassium feeders, any fertilizer that has the K component the highest, the N second, and P the least, would be advantageous since the majority of the banana make-up is Potassium. In any case, I don't think that the "P" component should ever exceed the "K". recommanded-15+10+30 or 15+8+27 E.g.
Joe Real: I use 6+27+27 XB with minors from BEST fertilizer brand. It achieves a nice balance of growth, pup and fruit production.
momoese: I use loads of steer and chicken manure as well as worm castings from my own red wigglers that have taken over the garden. I also use homemade compost and EB-Stone organic plant food 2-3 times a year.
Frankallan: I use aged rabbit manure
Rmplmnz: Compost tea wich is more or less a liquid version of compost. You take your solid compost, and soak it in water and let the mixture sit around for a few hours or a few days. Then you pour the liquid through a screen, or through cheesecloth or something similar to strain out the solid material into a bucket. What you have then is compost tea. Compost tea is great, because it is a very mild, organic liquid fertilizer that provides beneficial live organisms that improve the soil where you use it. It doesn't burn plants like store bought fertilizers can.If you can not find any of the above dump a bag of cow manure in the trash can and fill with water..
Bananimal: I use a custom fertilizer blend of 6-2-12 with minors. And especially important - I apply fert monthly. Up to 3 pounds when the plants are bigger and show real vigor.
FunSoCalTiger: I use a balanced granular slow-release such as Dynamite 13-13-13, Osmocote 14-14-14, Vigoro 17-17-17 or MiracleGro 10-10-10 every couple months or so and at planting. I also use any of several water soluable mixtures at 1-2 times the recommended doseage/frequency such as the balanced Peters Professional or MiracleGro Select 20-20-20 or the MiracleGro Tomato Food 18-18-21 (has slightly more K and also has some Magnesium). I also supplement with Epsom Salt each week to boost the Magnesium content at the rate of 1-2 teaspoon per gallon.
Nanaman: I use about 50% Jungle Growth potting mix, 40% composted cow manure, and about 10% added vermiculite, plus a few handfuls of Pre Plant Plus 7-5-7 organic fert. I fertilize about once a month with whatever I have on hand at the time, some times palm fert., some times 10-10-10, miracle grow, etc... I water them every day, sometimes twice a day if its really hot, which it usually is. In colder climates this mix may hold too.
Richard: 5 lbs of water-soluble 20-5-30 with micronutrients per maturing plant in the ground per year, applied monthly during the growing season.
joseryan
11-08-2013, 09:35 PM
I just applied N-P-K in my musa saba banana farm here in the Philippines specifically in Davao City.
I just dont have to accept all your recommendations regarding the application of N-P-K because it depends on the age of the banana, time of application and weather condition of my farm.
joseryan
11-08-2013, 09:46 PM
hi. i have a 17 hectares of musa saba banana here in the Philippines, Davao City.
can you discuss to me your recommendation regarding the right age of the banana plant to apply the N-P-K and the right time of application in a day.
Richard
11-08-2013, 11:21 PM
hi. i have a 17 hectares of musa saba banana here in the Philippines, Davao City.
can you discuss to me your recommendation regarding the right age of the banana plant to apply the N-P-K and the right time of application in a day.
In the tropics, you can apply per plant or matte net one pound of N when the plants are young, net 1/4 lb P one month prior to bloom, and net 1.5 lb K two weeks prior to bloom. (Tropics = zone 12 and higher.) Note if your N source (or P, or K) is 10% N, then you will need 10 lbs of it to achieve net one pound.
Alternately, you can apply a complete NPK fertilizer with ratios 2:1:3 (e.g. 16-8-24 or 20-10-30) throughout the year so that each plant or matte receives net 1.5 lbs of K.
lmswayne
11-12-2013, 07:10 PM
My - my- the brains on this page! I am with you Patty Meet you on the porch. After working through all that I think I am A little smarter. But I am in way over my head.
Who new growing bananas was so hard.
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