Alkaline water and dolomite lime

[wtf]

Hello everyone

i found this:

http://www.usu.edu/cpl/PDF/Optimization_of_SoillessMedia_High_pH_Water_Sources.pdf

this study by Utah state university says that with alkaline water dolomite lime ist not necessary and can damage plants. They used peat with perlite and/or vermiculite. Ph of medium was 4.5 and water-ph 7.8. In one week with regular watering, the ph of the medium went up to 7.5, without any added lime

my water ph is about 7.2 - 7.5 and its quite hard, the medium is peat-based and has coco, perlite and plant waste in it

I had severe problems after recycling my medium for the first time with added dolomite lime, just a few plants survived...

Now i wonder if anyone on this site has alkaline water, makes his own peat-based soilless medium and doesn't use dolomite lime? Is there any experience?

how does alkaline water effect recycled medium in the long run?

if i let it sit between uses and add acidifying material like wood, how long does it take to become acidic? i guess it would be quite fast?

i mixed a new batch of medium, without lime, and plan to put clones into that.. but i'm not sure if this will work out over time

wtf

 

[VerdantGreen]

its something ive been thinking about as well because my water is 8.5 - 9

what i do is add citric acid solution to the water and reduce the pH to about 6 before watering - and i seem to get great results first round but i dont currently recycle my soil.

dolomite lime supplies mostly magnesium as well as some calcium. your water hardness (although 7.5 isnt very high) would likely be from calcium, so you would need to find out more about this and perhaps add magnesium in some other form.

also bear in mind that bonemeal and rock phosphate are also liming agents which will raise the pH of your mix...

peat will reduce pH

VG

 

[SeaMaiden]

Generally, dolomitic lime is comprised mostly of CaCO3 and MgCO3 (calcium carbonate and magnesium carbonate, respectively). Both substances, being carbonates, work very well to keep pH values on the high end. This is why, in the aquatic scenarios I'm most accustomed to, we often use a substrate made of dolomite for those animals that prefer hard, high pH water. This includes fish such as African rift lake cichlids, and saltwater organisms.

Anyway, it makes sense to me that if the water is already high in CaCO3 & MgCO3, which is easily tested as carbonate or German hardness, adding more into the substrate could end up having a detrimental effect on it. However, that can be balanced in aquaria, in many instances I used to use peat moss itself to filter, alkaline water to soften and acidify.

The information presented in the paper makes perfect sense to me.

 

[moonymonkey]

check out the ph of organic grows.

 

[wilbur]

seems to me the study says it all ... and yr experience backs it up.

best, I think, to neutralise yr water before putting it on yr plants. takes out all the chemical unknowns that way.

and yeah, leave out the dolomite and you'll need to get Mag from another source.

 

[grapeman]

Alkaline water does not necessarily mean you can grow with immunity in peat soils.

A more substantial water/soil test is needed to tell you what you need to know.

 

[s00thsayer]

if you're recycling your soil it's very important to flush the soil with lots of water before harvesting the plant to make sure all the toxic salts are released from the soil. once the plants suck down all the water after flushing then you can chop your plant. i don't think it is a good idea to re-use soil immediately so you should let it mellow in a container somewhere so little microbes can work on breaking down the rest of the salts. i've got hard water and recycle soil without problems and never add dolomite or anything to the peat mix. as long as you flush out the excess salts you can reuse peat until it decomposes so much that it becomes too saturated when watered. i don't think coco can be recycled though so that may be your problem. i think coco retains salts and is not good for reuse. oh, and my plants do fine with a high pH so I don't mess with it. if i get a plant that has a problem with nutrient lockout in veg i just switch to a fertilizer with a different npk balance and it seems to cure the problem.