In the absence of a "perfect" citrus ratio with Mg, Ca,Iron and Zinc, it is best to go with excesses....like 16-16-16; you are only "wasting" a little P and K. Then supplement with some mineral applications that have the Mg, Ca, etc. Too much N, like ammonium sulfate or Urea will only encourage growth and limit flower/fruit.

Have you considered using Foliage Pro 9-3-6? The ratio is not 5:1:3 but it has the micronutrients and many on this forum, including me, use it successfully. Many also use it together with Osmocote Plus.

'Too much N, like ammonium sulfate or Urea will only encourage growth and limit flower/fruit.'

There's nothing inherently 'too much' with either AS or Urea or indeed any fertiliser. It depends on how much ones uses. AS is one of the best ways to provide N to citrus, especially if one's soil and/or water is on the alkaline side.

The way that quantity of fertiliser is usually calculated is calculating the amount of N required and then calculate the amount of other macronutrients based on the ratio targeted.

On the other hand, too much P is never a good idea as it can reach toxic levels in the soil, affect micronutrient availability and increase soil salinity.

One can fertilise with a 'balanced' compound fertiliser as long as the required amount of P is observed and additional N and K is provided by other means.

• Nitrogen and potassium are both water soluble, and can be easily flushed from he root zone if and excess has been applied. Phosphorus (P) on the other hand is not easily flushed out, and therefore builds up.

Nik,

I guess we are now friends.

Clear as mud, LOL.

So Until I can find a better alternative,how about Continuing to use a balanced time release, with additional ammonia sulfate, and try to track down some of those mineral additives? That’s basically what I did last year with my inground citrus and a couple in pots. They seemed to do OK. I was able to put a lot of growth on some winter damaged trees (that I had nothing to lose) by adding massive doses of ammonia sulfate. The Lemmontree dropped all of its flower buds when I did this, but it didn’t matter as it never would’ve been able to support any fruit anyways with the lack of vegetation. The previous year I had given nothing, and I had almost no growth on the trees. So was nice to see them doing something.

A shikwasa and early Mikan gave me a very large crop of fruit despite having used quite a bit of ammonia sulfate during the season.

Niceguy,

We sometimes over dose our young trees with Nitrogen, causing them to drop flowers and produce more growth.

While I have your attention, can I start hitting my trees with fertilizer now that they’re starting to sprout new growth? It’s still quite cool outside and we haven’t hit the main heat of summer yet. I wasn’t sure if the new growth is not coming from the roots and it something like stored energy, and I would risk damaging the tree by hitting it with fertilizer.

Yes you can. We routinely fertilise in ground citrus in February or early March before new growth sprouts.

In the average garden, unless your trees are large and heavy bearing, adding N is all that is needed. If the trees are young and not bearing N can be the only macro provided unless one's soil is heavily deficient in K and P which is NOT common or soil is very alkaline or saline which limits the availability of P. In a heavily cropped environment, N and K should be provided to about the same quantities with much less P provided. Actual quantities, timing and ratio per application depending on stage of fruit growth is a whole different can of worms..

PS. Be careful of your pH if you intent to provide ammonium sulphate to potted plants.. I would shy away from doing it although citrus seem to be quite resistant to pH root shock. Furthermore, depending on the potting medium, nitrification might not occur before N is flushed out thus making most of the N provided unavailable to citrus.

I agree with nik and Silica on the Phosphorous issue. From everything that I researched about nutrient management, there's no benefit from having lots of Phosphorous in your soil. So little P is used by the tree in the NPK ratio and since it is insoluble/can't be easily flushed, it can become a problem if you're fertilizing in containers.

What I think is the best option is to find a ratio with as low P as possible that is within your budget. Supplement with extra Nitrogen in whatever form you choose. If you need more K then you can choose to supplement the extra N and K separately to total a 5-1-3 ratio. Then have a micronutrient solution for soil soaking. Sorry I hope that makes sense! As an example, my method when I first started was like that but I used organic fertilizer. So I used 5-5-5 + bloodmeal (12-0-0) + micronutrient liquid solution. I tried to calculate the amount of 12-0-0 bloodmeal I applied to fit the ratio. I've bought other brands/ratios since then and still plan to mix and match. This way I don't have to feel stuck with one fertilizer all the time if I feel the tree is lacking something

Thanks, but this reminds me of the dilemma I hit a couple years ago when I tried in earnest to find a ‘proper’ citrus fertilizer. It’s the same problem I mention at the outset. I have to get some help locally to see if anyone can track down something close.

Until then, my original question still stands: with what I’ve mentioned I have to work with, and The inherent dangers you mention, is it best to give the potted citrus nothing? I’m using a standard all purpose bagged potting soil, and have added a bit of perlite.

It's never better to give potted plants nothing.

I think it seems difficult to cobble together a proper "citrus" fertilizer ratio because of the focus on the NPK numbers. It doesn't actually matter if the NPK combination of fertilizers do not give a proper citrus ratio. Calculating the actual amount of elements in each bag means can give the correct ratio.

The N-P-K numbers only tells us the % of element in the whole bag of fertilizer. If you calculate the total amount of N or K contained in the bag itself, you will know exactly how much you give your tree.

My 12-0-0 bag of bloodmeal is 5 pounds. This equals (12% of 5 pounds) 0.6 pounds of actual nitrogen in my fertilizer bag. It's suggested young trees receive 0.12 pounds of N. From there, I would know the exact amount of Nitrogen to give based on pounds applied. My other fertilizer 5-5-5 is also 5 pounds. The total NPK in that 5-5-5 bag is 0.25 pounds per N,P,K.

There are many people growing other plants that add their N,P,K separately so they can create their own ratio. They can do that because they know how to measure the actual amounts of each nutrient. You can use your above option of 16-16-16 and 21-0-0 if you want. If you double the ammonia sulfate you can get 58-16-16 which simplifies to 3.6-1-1 which is close. Knowing how to calculate the actual amount of nutrient in different fertilizers can help you get a closer ratio if you prefer though. Sorry I hope my idea came through clearer this time!

Thanks. That sounds basically like what I did last year. It would be nice to find those trace elements and minerals though. I’ll see what I can find in the stores this year.

For trace minerals, I have found it easiest to look for chelated mineral mix; it is a bit pricey, but not so much for small growers. I use a custom mix of 18-6-12 with 2% Ca and Mg, and 1% Iron and zinc.... you have to buy a large amount to get such a custom mix.

You may want to check this site: http://scienceinhydroponics.com/2016/03/the-first-free-hydroponic-nutrient-calculator-program-o.html

This guy wrote a program to custom formulate fertilizer from raw ingredients. There is a windows and linux version on his site. I have used it for fun. Never really tried to source individual components myself. Ignore the hydroponic reference.

Since you live in Japan it would be easier for you to find answers on Google for citrus fertilizers.

Another issue I remember running into a couple of years ago was with the trace element additives. All the trace elements are sold together very cheap here, however for some reason they’re combined with a highly alkaline mix, the purpose to “sweeten“ the soil. I can’t find any at the garden center that are ph neutral.

I remember someone mentioning combining this with the acid ammonia sulfate crystals would be a bad idea, as they will react and leave salts in the soil.

Ok, after much hunting I found the best selection in town.

They had a fertilizer labeled specifically to be used on Mikan (Satsuma). But all it is is a time release 8-6-6 fertilizer.

More promising, they had a time release fertilizer, 15-3-15, the only one I’ve seen which has such a low P and a high K .

I was thinking to buy this, and supplement it with my ammonia sulfate. However, given that they’re selling citrus specific fertilizer with an 866 ratio, why not just keep using my 14 1414 with ammonia sulfate?

As for supplements, I was having trouble reading the labels, but it appears that ones that include calcium and iron are also meant to be used to raise the pH of the soil, like lime, extremely alkaline. I found some apparently pH neutral supplements, but they appear to be only magnesium, magnese, and boron (ie 46Mg-5Mn-5B).

What say Ye?

" they had a time release fertilizer, 15-3-15, the only one I’ve seen which has such a low P and a high K .
I was thinking to buy this, and supplement it with my ammonia sulfate"... sounds like a good idea. As to the trace minerals, I think you would only need them once or twice per year; and a small amount; so the basic nature is probably not a big deal

For in ground citrus I would not be too concerned about exact fertilizer blend, many home citrus growing guides in the US recommend a simple straight balanced fertilizer like 13-13-13. In general citrus is tolerant of a wide range of growing conditions if you are not overly concerned with optimal yield.

.."if you are not overly concerned with optimal yield".... that is it; in general most citrus absorb nutrients in the 5-1-3 ratio Meyers like 3-1-2; but if you just want pretty green trees, in ground citrus can get by with just Nitrogen.

Just be careful of mixing fertilisers. Not all fertilisers can be mixed with each other. Fertilising with one and then after a few days with another poses no problems in general.

Using 15-3-15 supplemented by ammonia sulfate sounds like the best combination.

14-14-14 with ammonia sulfate is okay but K will be as low as P. Unlike phosphorus, (K) potassium can be lost leaching through the water. Containers are always watered more often than inground so it's better to go for 15-3-15 in the end. If you get the 15-3-15 and the K leaches from frequent container watering, chances are it'll still be a bit higher than P since the difference was originally much larger

Ok thanks guys. I’m going to primarily focus on container citrus now, as this winter destroyed most of my inground citrus. I’m still a little unclear about the trace elements. Is that product I mentioned above sufficient for container citrus? How about using the alkaline mix instead ( as it appears more comprehensive, including iron etc.), if I wait a few days before applying ammonia sulfate?

Additionally, what is the adverse effect of not following these guidelines, for example if the P ratio is too high?

Wow! Finally found something. It’s time release 10-2-6 with 1 part magnesium. Found it at a one of those pokey little hardware stores nearby. Ironically it’s just produced for vegetable gardens. It’s also a bit of a rip off, double the cost of that stuff I mentioned above and triple that up a standard 14 14 14 mix.

Trace elements: having a bit of trouble reading some of the labels, but if I understand correctly, they don’t sell a complete mix of trace elements or the separate components, without adding agricultural lime to raise the pH. A bag of this is extremely cheap, and has all of the elements you mentioned above iron copper magnesium etc., except it’s also 46% alkaline agricultural lime meant to raise the pH. Is this stuff safe to use for container citrus? This shouldn’t be too much of a problem if I’m not needing to use ammonia sulfate?

I’m thinking to buy that rip off time release, and sprinkle a bit of that agricultural lime trace element mix occasionally. Sound like a plan?

By the way Nick, I could find N and P sold separately but no K.

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Common potassium ferts I would use in pots (and in ground)

Potassium sulfate K2SO4 about 0-0-50-(18S)

Potassium nitrate KNO3 13-0-44

The first one is slower acting but more suitable for alkaline soils. The second one provides some N too. Both of them provide a lot of K so a little goes a long way. I doubt that you can find them packaged in small quantities. I buy them in 50Kg bags but I use a lot... They are fairly cheap this way, less than 50 eurocents per kilo. Over here specialised shops can mix 'n match small quantities of fertilisers. Don't be afraid to provide a bit more K to citrus than the mythical 5N:3K ratio.

If you really want to know what is going on, do what we do... we do a leaf analysis twice per year; that tell you what the plant has or needs. Soil analysis only tells you what is in the soil; not what the plant has or needs. Texas A&M citrus center taught me that; they tell their growers that; but most still put the ferts they think they need; because "that is what they have always done"

Thanks nick, didn’t see thise there, but I’ll keep an eye out for them. John, the local agricultural office was fairly limited and I don’t recall them offering any such service, paid or otherwise. I did get them to do some soil sample tests, but it was quite an event to get a translator and go down there.

I’m about to add that agricultural lime and trace element mix. Is there any rule of thumb to make sure I don’t overdose potted citrus, or is that something I don’t need to worry about?

John

I like your leaf analysis idea

How much do you think it would cost for me to get a leaf analysis of my citrus tree here in Cincinnati'

By the way, I hope I translated the ingredients correctly:

calcium carbonate: 89%

Humid acid: 1.1%

soluable magnesia:0.65%

soluable magnese; 300ppm

soluable boron: 630

iron: 400

zinc; 85

copper; 16

Molybdenum: 2

It also states it is “46% alkaline”.

Under dosage (outdoor), for “fruit trees” it recommends 140~160g per square meter.

That's basically 'lime'. I would not use it in pots unless you use a very acidic peat based mixture. It is probably something recommended to neutralise a bit the common acidic Japanese soils.

Here in Louisiana, the LSU soil testing lab will do leaf testing for $10-$18 per sample depending on the level of testing desired.

This is getting ridiculous! It’s like every option has a problem.

Ok, looks like 15-3-15 is the best deal, and the extra potassium is negligible and harmless. I can also buy a bag of 46-5-5 (Mg-Mn-B). Beyond this, I can’t find trace element supplements that are not bundled with lime. So I have to do without, or risk raising the pH.

15-3-15 will be fine. Don't give it more thought, you have given it too much thought already... If you can find a foliar fert containing trace elements, this will be good if sprayed twice a year in early spring and in autumn. Sometimes these contain also N other times not. Any will be fine. About the 46-5-5, apply that sparingly. Zn is mostly what's missing from it.

Human urine is 4-1-0. So if you use 3 units of urine to get 12-3-0 with your 15-3-15 you will get 27-6-15 which is very close to the 5-1-3 ratios weee seek.

With or without last evening's pints ponc?

Ok thanks guys. You are correct, I give an undeserved amount of time to silly details. There’s an element of diversion hobby after all.