Alkali or acidic fertilizers?

[Austin]

I have been using a vegtibal fertilizer that has every micro and macro nutrient except for calcium, making it acidic (at 5-5.5 once mixed)

is there a fertilizer that is widely used that is more alkali?

I ask this as I intend to use a more PH neutral potting mix come summer and spring when I start digging up plants from the landscape, and I thought that perhaps using a more or less acidic fertilizer would be the way to go to adjust the potting mediums PH lvl

 

[63pmp]

It's not the presence or absence of calcium which affects pH.

If its vegetable based, i.e. organic, then the acidity comes from the release of organic acids which develop during the composting process.

Generally, if you had a choice, an acidic fertilizer would be preferred over an alkali one as most plants prefer acidic soil conditions.

Organic based fertilizers will always be acidic, as explained above. Chemical fertilizers tend to be neutral to acidic, depending on the contents. Typically though they are slightly acidic as alkalinity can cause some elements to precipitate out.

The things that cause pH drift in potting mixes are the types of nitrogen available for plants; nitrate and ammonium. Depending on the plant species, nitrate tends to raise the pH, while ammonium lowers the pH. Dissolved bicarbonate in water causes soil pH to rise, even though the pH of the water may be acidic, the presence of bicarbonate will eventually raise the soil pH.

So a fertilizer with high nitrate content may have a pH of 6, but because plants are taking up nitrate they release bicarbonate from the roots to balance cellular charge, and the soil pH rises as a consequence. If a fertilizer is made up of mostly ammonium, the roots release acidity to balance the charge, which lowers soil pH.

Regarding pH of your medium: Stick with the current fertilizer, but dilute it more then you are currently doing. Plants don't need a lot of fertilizer when first dug, but a little bit of fertilizer will lower the soil pH if your concerned about it. A slightly lower pH may help with micro organisms. How much pH changes will depend a little on the materials you are using in your potting mix. Things that are high in CEC, like zeolite, will buffer the soil pH, so add some fertilizer, or a pH down solution. If they are mostly inert materials then I wouldn't worry about the soil pH as it will change quickly anyway. I think zeolite should only make up a low percentage (<15%) of the potting mix.

Regards

Paul

 

[Stan Kengai]

I would add that most plants will thrive in a pH range of 5.5 to 7, but nutrient uptake is generally greater at the lower end of this range. There are obviously some outlier plants (azalea and liquidamber at the lower end, and beech at the upper), which prefer the edge or outside of this range and are more sensitive to pH. If you don't want to concern yourself with soil pH, use humic acids, which act as a buffer and make fertilizing more efficient.

 

[63pmp]

Is that all beech Stan?

I was not aware beech were acid sensitive.


Paul

 

[Stan Kengai]

Is that all beech Stan?

I was not aware beech were acid sensitive.


Paul

My experience is with Fagus crenata (Japanese beech), and I've found that in a containerized situation they prefer to have a pH between 6.5-7.5. They can live outside this range, but they won't thrive. To clarify, I would say beeches aren't acid sensitive, but they have a more narrow ideal pH range than most plants.

 

[Austin]

I was just curious as I have some Texas ebony (more alkaline) and mostly acidic loving plants willow ginko maples, and thought of using a fertilizer rather than amending soil to adjust PH

but it appears that nuetral PH would work for everything regaurdless

 

[63pmp]

Thanks Stan,

That's certainly provided something to think about.

Austin,

Problem with keeping pH neutral is that some plants will be unable to take up the nutrient, iron, while others may be sensitive to ammonia, which forms from ammonium at these higher pH's. My understanding is that alkali lovers are very good at extracting iron from the soil, so when grown under acid conditions they simply overfeed on iron and poison themselves. The opposite is true for acid loving plants, they are not very good at extraction iron, and so starve in alkali soils.

You can adjust the fertilizer, which means a special mix for the alkali lovers, or, you can simply add some dolomite to the ebony plants pots every month or so.

 

[Austin]

Thanks Stan,

That's certainly provided something to think about.

Austin,

Problem with keeping pH neutral is that some plants will be unable to take up the nutrient, iron, while others may be sensitive to ammonia, which forms from ammonium at these higher pH's. My understanding is that alkali lovers are very good at extracting iron from the soil, so when grown under acid conditions they simply overfeed on iron and poison themselves. The opposite is true for acid loving plants, they are not very good at extraction iron, and so starve in alkali soils.

You can adjust the fertilizer, which means a special mix for the alkali lovers, or, you can simply add some dolomite to the ebony plants pots every month or so.

some reading I did suggested adding pot ash to make mixes more alkali, and of coarse lime or compost to make for a more acidic mixture.

do you or anyone else following this thread know if either of these methods are effective?

I imagine that pot ash is more of a temporary fix while the compost would be a longer term solution while still being a temporary fix (until enough would be mixed in).

I'm curious about this due to a PH imbalance I unknowingly created in 4 pots, and I intend to make a larger bed to thicken trees in that I would like to know what I'm adding to it be for I start so amending isn't needed in great amounts.

theorized potting mix would be 1 cubic yard of each of these elements

lava rock

turface

pine bark