Dolomite Lime - Help Question

[greenspiritz]

I've been away from the forums for quite some number of years, but i'm back for a while and i'm hoping someone could help me with my issue please.

There's so much different advice i have read online about dolomite lime. So i thought i would chime in here for some great advice.

I have recently bought some (Westland Jack Magic All Purpose Compost). I tested PH from the run off and it was 5.2 - 5.5.

I did this test after having a couple of cuttings in the soil for a few weeks only to notice they started getting deficiencies in Calcium, Magnesium and over all bad appearance, I did not feed any nutrients only water.

So i got a clean pot and some new soil from the bag and ran some clean water that had a PH of 7.5 just to see what the PH result was. The result was 5.5.

My question is, i have bought some dolomite lime that is of flour consistency, I'll be growing in 5,7 litre pots in a SOG method. How much dolomite lime should i use in UK measurement per 5,7 litre pot to get a PH of 6.5?

I hope someone could help me with this? Thanks for looking

Stay safe Green

 

['Boogieman']

It's kinda a trial and error thing, 1 gallon is roughly 3.7 litres. I add 1/2 a cup per cubic ft of soil mix so let's break that down.

1/4 - 1/3 tablespoon per liter

1.5 tablespoons per 5 litres - 2 tablespoons per 7 litres should be fine.

 

[Teddybrae]

Mate ... I 'm a soil grower and measuring the run-off pH will tell you nothing. You need to test soil pH. There are cheap, accurate kits for this. You need a pH around 6.5 (if you're a perfectionist Icmag member and soil grower Troutman knows the exact number).

Look on yr bag of soil for a pH number. Or ask your compost supplier. But best to buy a soil pH test kit cos you may need to know the soil pH at any stage of your grow.

 

[greenspiritz]

I did contact (Westlands) about this issue, and this was their response to my question. The PH stated is 5.5 - 6.0. But the run off is like 5.0 to 5.5 even after a good little flush, the plants at first seem really happy in it until a few weeks down the line and then they start showing Calcium and Magnesium Issues, which i've never had before with other soils. Something is definitely missing.



Good afternoon



Can you please send me some photos of the deficiencies you are seeing, as we can suggest different fertilisers to help? We can identify the deficiencies from the leaves of the plants for you.



Do you calibrate your pH for acidity with vinegar or pH 4 buffer as well as pH 7 buffer? When you say PPM, do you mean EC? This is the electro-conductivity of the ions in the fertiliser, and the rates can vary depending on the feed used by the plant at the time , e.g. more nitrogen used in spring but more potassium at flowering stage.



It may be possible that the lime has not been evenly distributed when the peat was blended before packing, so using Dolomite lime or garden lime will help.

We do not publish an NPK ratio or the secondary element ratios (Ca, Mg, S) as they are variable depending on the ‘H’ layer of the peat bog that is harvested.



We also manufacture a Houseplant compost for indoor plants, as well as Bonsai, Cacti, Orchid ( Dendrobium or hybrids such as Miltonia do well in this) and Citrus versions. The Household one has a pH of around 6.5, and all of them contain pieces of Seramis ( baked clay with tiny holes) to help with watering.



I hope this is useful to you, and I look forward to seeing your photographs so I can help you further

 

[greenspiritz]

This is what i emailed them.



Hi,

I've been using your Jacks magic compost, i looked at the Safety Data Sheet and it says the PH of the soil is 5.5 - 6.0.
Anyway, I've been having some nutrient deficiency issues with it.

So i decided to test it straight out the bag in a new pot with nothing in it, i flushed some fresh clean water that had a PH of 7.5 (Tap water) and from the run off, i was getting a reading of 5.1. Then the second flush 5.4.

The PPM level is also testing high at 950PPM, so i flushed further on and lowered the PPM to 350PPM but still a PH reading of 5.4. I'm hoping for a solution to this, because i really do like the soil and its texture.

But what is it's chemical analysis (NPK,Mg,Ca) ect. I'm hoping to get the soil PH up between 6.5 - 6.8, would it be advised to use Dolomite lime with your Jacks Magic, or do you have another indoor soil compost with a PH between 6.2 - 6.8.

Both my PH Meter and PPM Meter are both calibrated using Hm Digital Tds and Ec Calibration Solution &
ph buffer 7 by growth technology