I have a 25 lb bag of Peter's 21-7-7, an acidic soluble fertilizer. I bought it to use with my blueberries, but I don't use very much and still have a lot of this 21-7-7 fertilizer unused. I'm wondering if there is a way I can use if as a regular fertilizer, on my vegetables. Can I mix up a batch and add something to the mixture that will cut the acidity down to a usable level? I have plenty of wood ash, would that work as an additive?

I'd appreciate any suggestions....

John

I use an acidic fertilizer on my blueberries at 1/2 cup per bush. I have 5.
In my experience, 21-7-7 is not really too acidic.
I would think that if you mixed it with 20-20-20, that might solve the problem for you. A while back, I used 30-10-10 on my Rhododendron and Azaleas. That was a pretty good blend.
On my veggies, perennials and annuals, I use the 20-20-20. Have been for about 15 years now. Tomato yields are very nice. Sometimes I have so many tomato's I seem to be knee deep in them.

Peter's lists the 21-7-7 as having acidity of 1518 lbs of calcium carbonate equivalent per ton. The 20-20-20 shown as 555 lbs of calcium carbonate equivalent per ton...so the 21-7-7 is 3 times as acidic as the 20-20-20. I also use 25-5-15 which is shown at 608 lbs calcium carbonate equivalent.

I could try mixing, but I don't know what the exact effect would be on the acidity. Would there be a chemical reaction that would produce an unusual result? I want to end up with a mixture that is close to the 20-20-20 or the 25-5-15 acidity level. First step is to find a good way to measure the acidity of the mixture.

I don't think there's any fixing it. The problem is the source of nitrogen... Fertilizer that's more neutral has more nitrate nitrogen and fertilizer that's more acidic has more ammonium/urea nitrogen. Your fertilizer is all ammonium/urea nitrogen with an added 15% sulfur to make it even more acidic. The absolute only thing you can use your Jack's 21-7-7 on are acid loving plants. Adding other materials will not change the acidic properties of the nitrogen.

Strawberries and potatoes do well in acid soils. If you grow them, use it on them.

Is fertilizer so expensive that you can't afford the right kind for ordinary plants?

Without knowing the characteristics of your soil there is no way to advise you. The interaction of multiple fertilizers and amendments is unpredictable without more information.

Gee, save the acid food for the acid lovers.

Buy some ordinary food for the rest.

Now Hortica, be nice. Actually, that fertilizer if very expensive, at least it would be a major ding to my wallet. I can understand wanting to figure out how to use it in some other way. But unless your soil is very alkaline, its just not going to work. Fertilizer doesn't go bad (if stored in a dry place) so stick it in the shed and use it up slowly.

I read a warning on the label saying if your soil is already acidic, don't use. It seems it would make a better pH fix than a plant fertilizer. I guess you will have to figure out what the soil pH is in your area to get a better idea on what you can use it on. Unless your water is being piped in from far far away, you can get a good idea of soil pH by doing a pH test on your tap water with a packet of cheap litmus paper. You can test your soil pH too - mix a little dirt from your yard with distilled water, shake it up real good and touch the litmus paper to it. Don't use the dirt on the surface, dig down several inches. You don't want to test the pH of what the dog left behind.

How about adding amendments for soil pH- lime?

Lucy68 said:Unless your water is being piped in from far far away, you can get a good idea of soil pH by doing a pH test on your tap water with a packet of cheap litmus paper.

If your "tap water" is from an individual well, then (and only then) might this be true. All municipality water is treated, and the pH of the water is raised to prevent major corrosion of the delivery system. For those with water that is naturally more acidic, the pH change is hugely significant. For those with naturally higher pH, the pH change is less. Alkalinity also plays a role.

Acid based fertilizers are never a permanent fix, but maybe be temporarily useful, depending on the soil type. The acidic nitrogen compounds in dog pee is what kills the grass, but the danger dilutes and washes away with the first heavy rain. Even sulfur is not permanent, as once it chemically changes to compounds that increase acidity, it also becomes very mobile in the soil and vulnerable to washing away.

Lucy68 said: Now Hortica, be nice. …

Lucy68 said: … Unless your water is being piped in from far far away, you can get a good idea of soil pH by doing a pH test on your tap water with a packet of cheap litmus paper…

Being that the OP is in LA the water is being piped in from far, far away and is quite basic. The local water department can supply a report of the hardness and alkalinity (which is awful).

Lucy68 said:. …
You can test your soil pH too - mix a little dirt from your yard with distilled water, shake it up real good and touch the litmus paper to it. …

This will not give the OP an accurate idea of the reserve alkalinity of the soil. A full soil analysis would do that. Some county Extension Agencies used to do this for free, but I don't think any California ones do.
Again, we don't have enough information to advise without knowing more about the soil.