Sulphate of Potash

[David Nicholson]

.........They changed the label but is it still 50% peat?

Mark, was that meant to be written as a statement or a question?

[mark smyth]

well, if it was 50% peat and they changed the label it could still be 50% peat and they are lying to us

I asked them about their top soil not being top soil but a mix of peat and sand and whatever. Their answer is "We do not put any peat into this product and so it is unusual and unfortunate you have received a product in this condition". Time to buy another bag and repeat my mix some in water test

[Paul Cumbleton]

Hans J asked me (in a personal message) about when using sulphate of potash on its own, what rate to use if wanting to dissolve it first and water the solution in (rather than sprinkling the powder  onto pots like Ian Young does). He wondered if 1 gram per litre of water would be a reasonable amount to use. I thought my reply might be of general interest, so I'm posting my reply here:

Yes, 1 gram per litre would be a sensible amount to use for sulphate of potash. I have a conductivity meter that I use to measure the strength of fertiliser solutions. The units of measurement are microsiemens (μS). So I dissolved 1 gram of sulphate of potash in 1 litre of water and measured the resulting solution. The reading was 1817μS. How does this compare to other fertilisers? I have measured many other fertilisers before and I find that if made up at the full strength as recommended on the packet, they very commonly come out at about 2000 to 2500μS. Rather than giving you grams per litre, many powdered fertilisers for amateurs come with a scoop in the packet and they tell you to put a certain number of scoops in a certain volume of water. If you actually weigh the content of the scoop and do the maths, you will find that for the vast majority of fertilisers, full strength equates to 2 grams per litre. Here are my readings from the conductivity meter for a couple of commonly used fertilisers made up at the full recommended strength (2g/l):

Miracle-Gro (NPK = 24 - 8 - 16)            : 2500μS
Chempak No. 8 (NPK = 12.5 - 25 - 25) : 2410μS (often used by alpine growers in the UK)
The sulphate of potash at 1g/l was        : 1817μS

Note, these were made up in our local tap water which on this occasion started out at 170μS before adding any fertiliser.
You can see that 1g per litre of sulphate of potash would produce a solution of reasonable strength. If you were to use a rate of 2g per litre (like many of the balanced fertilisers) this would produce a reading of over 3600μS which would be very strong indeed. So I would stick with the 1g/l as a guide.

Paul

 

[Hans J]

Hello Paul 

Many thanks for your interesting work !

I have  watered today all my winter growing bulbs with this 0,1 % solution :
Acis ,Sternbergia ,Scilla ,Galanthus and many of my South african bulbs ( exept the summer growing )

For watering I have used rain water ....the rain water here is not acid ...it is more or less neutral ( ph 6,5 - 7,5)
so I have add  vinegar essence ( 25% ) ...so I have now 6,0 - 6,5 PH
In case I have not enough rain water I must use domestic tap water ...it has also around 7,0 PH ...but total hardness of 10 ° 

Paul - what you think ?
Should I watering again with Potassium Sulfate ( 0,1% ) in maybe two month ?

Best wishes
Hans