pH Conversion Question

There are a tremendous amount of resources on the internet, including DG, that provide the pH requirements for trees, shrubs and plants. But when I go into a garden center or home improvement center to buy plant fertilizer such as Jobe's Fertilizer Spikes, I see that the label only includes a generic statement such as "...special formula for acid loving evergreen trees &shrubs..." and then has the guarranteed analysis percentages. Can someone on this forum provide a corresponding pH range for the percentage numbers below?

25-10-10
16-8-8
16-4-4
15-7-6
13-4-5
12-16-12
11-5-7
10-20-20
10-15-15
10-13-13
10-10-4
8-24-8
5-35-10

Thank you for your help.

Luke

Not really is the very quick answer. Much depends on what ingredients, i.e. the source of the NPK in that particular brand, that are used in the fertilizer itself.

pH has an effect on the levels of nutrients released to the soil and fertilizer brands/mixes can be formulated for low pH but it's not a great deal to do with the ratios of NPK contained therein.

There are some very inexpensive ways you can increase or decrease the pH of water. I do this with my fish tanks. How much impact it would have in water soluable fertilizers I don't know. Vinegar will lower pH (more acidic) and baking soda will raise it (more alkaline). Limestone also raises pH if you have it available for free or cheap, an peat (not really cheap) will lower it.

I am starting some berries this year. Blueberries, raspberries in the ground and strawberries in a container. Could someone please tell me the ideal PH for these plants. Thanks.

blueberries--> acidic (like hollies or azaleas). use gardeners sulphur on alkaline soils, or use hollytone to fertilize.

raspberries/strawberries. slightly acidic is fine. no need to use anything particular unless your soil pH is very untypical for MD.

LUKE:

The NPK ratio of fertilizer sticks will not give you any information about the affects on pH.
However, some fertilizer types contain acids which help lower soil pH, while others contain salts which displace negative ions in the soil thus raising the soil pH. A good example is ammonium sulfate. Both products (ammonia + sulphur) will lower pH. Whereas potassium nitrate, for example, tend to raise pH.

I would go with one choice of fertilizer based on the requirements of the product (green leaves, flowers, perennials, annuals, etc) and then adjust pH with lime if you need to bring it up. If you have alkaline soil, then use fertilizers which are stated to be good on acid lovers (hollytone, miracid, etc) irrespective the type of plants you grow. Normally you can target a soil pH of 6.0-7.0 and you would be A-OK.

For flowering/fruiting plants use balanced fertilizers or fertilizers where 2nd and 3rd numbers are higher (5-10-10, 10-20-20, 20-20-20, 15-30-15, 10-15-10, etc). For foliage plants and grass go with ratios where the first number is significantly higher: 6-2-0, 10-2-6, 29-3-4, etc. Dont use the latter group on flowering/fruiting plants.

Luke, from your list:

The 3 numbers are in order: N-P-K (nitrogen - phosphorus -- potassium)
25-10-10 --> lawn fertilizer (*)
16-8-8 --> lawn fertilizer (*)
16-4-4 --> lawn fertilizer (*)
15-7-6 --> lawn fertilizer (*)
13-4-5 --> lawn fertilizer (*)
12-16-12 -- balanced or "flowering type" fertilizer
11-5-7 -- lawn fertilizer (*)
10-20-20 -- good for most fruits and flowering plants
10-15-15 -- same as above
10-13-13 -- same as above
10-10-4 -- same as above on soils high in potash
8-24-8 -- flowering type fertilizer
5-35-10 -- flowering type fertilizer on soils deficient in phosphorus (do not use)

(*) Those marked with the star, can also be used on perennials, shrubs once in early spring, but use it sparingly and then switch to a balanced fertilizer (14-14-14, 20-20-20, 10-13-13, etc) if the plants are flowering/fruiting. Generally it is safer to just use the balanced (10-15-15, 10-15-10, 14-14-14, 20-20-20, etc) fertilizers unless it is purely green plants.

I would not use the "phosphorous boosters" (5-35-10) unless your soil is lacking in phosphorus. I know it is today sold as a "wonderdrug" to make plants flower, but that is more hype than reality in my opinion. I much prefer the balanced, or those fertilizers with slightly more phosphorous: 10-15-10, 15-30-15, 10-13-13, etc.

My recommendation for flowering/fruiting plants:
12-16-12, 10-20-20, 10-15-15, 10-13-13, or 8-24-8 to be safe.
I am very partial to 10-20-20 for flowering plants, but any of the grades mentioned will work. So will the slow release coated fertilizers like OSMOCOTE 14-14-14, MULTICOTE 14-14-16, NUTRICOTE 14-14-14, etc.

As you can guess from above, it is not the numbers themselves that are important. It is the RATIOS internally between the numbers.

Kenneth

Kenneth--

You seem to have a good handle on pH. I want to make a seed-starting/potting-up soil mix that has a pH higher than 6, but not sure how to accomplish this since the basis of my mixes is usually peat. I don't have access to any new amendements just now (not until May) so have to work with what I have on hand: lime (probably too slow acting) plus the usual bone meal, blood meal, wood ash. I have peat, vermiculite, perlite, good compost (but a bit too new to use too much of) and regular garden soil, if I can find some that isn't still buried in snow and frozen!

I thought you might have a sense of how little peat I'd need to use to reduce the pH yet still have a good growing medium.

Any suggestions will be very appreciated! My plantings generall do just fine, but this year thought I would cater more to the plants that prefer a high pH and see what difference it makes to the final outcome.

Just a little note on the fertilizers. I was using one of those 5-30-5 mixes when I didn't know any better. The flowers were great but they were on some of the weakest, sickliest plants you have ever seen! They tried to bloom themselves to death. Luckily a friend told me what I was doing and now they are happy healthy plants.

Chilko, You can add lime, but use a very fine grain. wood ash can be used to raise soil pH also and is a good source of potassium, just dont overdo it. it require just a dusting. You can also use a mainly nitrate based fertilizer instead of the urea/ammonia based fertilizers and that will help keep the pH up.

Using 5-30-5 is ok as a single application around blooming time, but should not be used excessively.

Oh, good information, didn't realize that wood ash would help much. Since it is all from pine, which is itself acidic, I shulda thunk.

Wood ash tends to be alkaline and raise pH. You have to use it sparingly because wood ashes can build up the potassium in the soil to very high levels and create problems.

This is probably getting technical, but I do wonder about things...the soil in a pine forest is very acidic. What is happening then when the pine is burned, to cause the resulting ash to be alkaline? Is ALL wood ash alkaline? Would the pines themselves be acidic, or just cause the soil to become so? Certainly our well water is highly acidic.