[screamingcow]

High - we are quite new to this and got our allotment 2yrs ago - 1st year was too late to do much - but last year we were quite successful. i was reading an artical on this website regarding PH etc so bought a PH meter. It says my soil has a PH of the 3 (maybe lower as this is a low as my meter goes!) , i have put a fair amount of manure down also super phosphate (does super phosphate lower PH ?? , thought that was sulphate ) anyways i was thinking of putting lime down to increase it - but it says not to do that on here ! so what should i do . Also i wanted to give the plants nitrogen via dried blood or urea - but that will apparently lower the ph further ! what bits of N/P/K decrease PH and what have no effect or increase .   bit stuck here , of course it maybe the meter is faulty - but when i stick in my back garden it reads about 6 and in water 7 so  i am assuming PH3 will mean death to everything ? help...... 

[galen]

I think you're confusing your increases / decreases of pH. Adding lime will decrease the pH, ie take it towards pH7, which is neutral. When it talks of not putting lime down it means at the same time as manure - you have to wait for the manure to break down a bit before lime is added (and no I don't know for how long !  )

All the manure you've been adding, being acidic, has, by the looks of things, drastically increased (towards pH1) the pH in your soil.

[Swing Swang]

Something has to be wrong. White vinegars contain 5-10% acetic acid and have a pH of approximately 2.40 - 3.40. The run off water from is peat bog is slightly less than 5.0. Try a different meter or a different kit (perhaps one of the cheap chemical varieties).

SS

[savbo]

as has often been said on here, the cheapest liquid testing kit is usually a lot more accurate than low- and mid-price meters...

M

[Ivah]

If you say it reads 7 in water it is working to some extent but as others have said 3 is very unlikely / impossible. Try shaking some soil samples with water, say ¼ of jam jar of soil topped up with water, and then testing the liquid after it settles.

[Babstreefern]

I can verify my PH when I swapped my plots.  My first plot was perfect - PH7 (give or take .1)

On the one I swapped, my PH level was off the scale below PH1 - so I added lime last October/November - plenty of it.  Its now up to PH5 in some parts and even PH7 in other parts   I've used both meters and chemicals and they both read the same.

But don't forget, different veg requires different readings.  Brassicas love PH7 or higher, whereas spuds love acid - PH4, give or take

[bigben]

As Swing Swang has indicated - if you are getting pH readings below 3-4 treat them with suspicion as 4 is about the lower limit for the majority of plant growth. While a pH of 1 is the same as stomach acid and would be corrosive. Either the meter is not reading correctly or you just happen to be testing the bit of soil you spilt battery acid on!
Adding lime will increase the pH making the soil less acid but more alkaline. If the soil is already acid the pH will move upwards towards 7 (neutral), while if it is alkaline then lime will make it even more alkaline ie above 7.

[Salmo]

Lets put the pH thing right before Sc get too confused.

The pH scale is logrithmic, that is to say pH7 is 10X the value of Ph6 and so on. Hence the difference between bottom and top i.e. ph1 and pH14 is huge. The nuetral point on the scale is pH7

If we add lime we make soil less acid and the pH value increases.

For most crops a pH of 6.5-7.0 is ideal. Much above 7.5 or below 5.5 and we start to see nutrient defficiency symptoms due to nutrients being tied up and unavailable to the plants.

I very much doubt if soil would ever get down to pH3. Throw your meter away and buy one of the cheap pH testing kits with tubes. You only need pH, no other nutrients.

The most useful test for the gardener is one for an area of the plot rather than a spot test. To do this use a narrow trowell to take out soil samples down to about 6 inches deep all over the area you want to test. Put these in a bucket until you have half a bucket full. Mix it up thoroughly and then test samples of this. It might also be useful to take another sample from deeper as sometimes the surface may be OK but it is acid down below and the roots cannot grow there.

[bigben]

At the risk of even more confusion- one further "clarification" - the pH scale is actually a negative logrithmic scale of Hydrogen ion concentration so pH6 is actually 10X the value of pH7 not the other way round. Roughly speaking a solution where the concentration of hydrogen ions is 0.0000001M is pH7 (like water) while a solution that is more concentrated 0.000001M would be pH6, a weak acid. If we have more 0 s in the figure the solution becomes weaker and the pH higher.

Much of this detail can be safely ignored  - my main point in my previous post was to be suspicious about pH values less than 4. As Salmo says aim for 6.5-7.

screamingcow would be right in saying pH 3 means death to everything, but more likely it means your meter is not accurate.

[JayG]

Seems to me you will not trust your pH results unless you either borrow a different meter or buy a pH testing kit as suggested.

You do not say when you added the manure; the principal objection to liming and manuring at the same time is that some of the nitrates are converted into ammonia, which being a gas is lost to the air hence losing some of your valuable nitrogen content. This is much less of a problem if the manure has been dug in and the lime is sprinkled on the soil surface as most of the release of ammonia will happen underground where it will re-dissolve in the soil water and be retained as a food.

If further pH testing does confirm low pH levels you may find this article useful.

[savbo]

digressing a bit, but 20years ago I visited a friend who was a bug expert and he proudly showed me the pond he was building which had planty of limestone and concrete at the bottom to make it really calcium rich for the snails and other invertebrates he wanted in the pond.... went again a month or two later and he rather sheepishly showed me a pool of what looked like milk, had some very high pH (can't remember exactly what it was now) and was practically toxic to all life...

I think he cleared out most of the limey stuff and it worked OK in the end - but it shows you dont need much lime to shift the pH

M