[RJR_38]

Once again my main crop potatoes have got magnesium deficiency. I have watered them with Epsom salts which I was loathe to do as it isn't really organic and I am organic really - but I don't know any other solutions.

Is there anything I can do over the rest of this season to stop this happening next year? What is a good, natural source if magnesium?

[Martifromduram]

Hi there, cold, wet and high potassium can block the uptake of magnesium, this might be the cause of the deficiency?

[RJR_38]

Ok, I could try growing them on the sunnier half next year then. How would I solve too much potassium?

[solway cropper]

A lot of things can cause symptoms that look like magnesium deficiency so you need to figure exactly what's wrong before deciding on any course of action. A soil analysis is required before you can say for sure whether any additional mineral is needed to correct the balance.

Potatoes require huge amounts of potassium so, unless you are applying large amounts of chemical fertilizer I would say an excess of that element is unlikely.

I reiterate that you really need to discover what the problem with your spuds really is.

[Yorkie]

Have you been feeding them with anything?

[RJR_38]

No, I haven't fed them with anything. I have just given them a watering with Epsom salts which seemed to help last year. They look identical to all the photos I have seen of magnesium deficiency and they seem to follow the same pattern with the lower leaves being affected first (it also seems to be affect main crop much more rather than earlies or second earlies).

I am loathe to pay for an expensive soil test to be honest.....

[mumofstig]

Once again my main crop potatoes have got magnesium deficiency. I have watered them with Epsom salts which I was loathe to do as it isn't really organic and I am organic really

I thought it was organic, as it's separated from mineral water so I Googled...........

More technically known as magnesium sulfate, Epsom salt is a recognized natural source of magnesium and sulfur,

Delicate filtration processes are utilized to ensure an end product with no perceptible impurities that dissolves quickly and easily

Epsom salt has become a popular and well-reputed supplement in organic gardening. With the recent push towards “green” living, Epsom salt is an ideal answer to a variety of organic gardening needs.

http://www.ultraepsom.com/what-is-epsom-salt.html

[beesrus]

I wouldn't pay out for a soil test. Your neighbours will tell you what the soil is like. Sometimes what is assumed to look like a magnesium defficiency is more often than not just an all round lack of fertility, especially on depleted allotment sites.
Testing soils at no small expense is for farmers, commercial or show growers and the like. Far too easy to get too technical and miss the real reason for ailing crops.
Two years ago, my present plot had terrible magnesium-like disease of leaves on potatoes and all brassicas. All but the easiest of crops were yellowed and barely acceptable, and those poor crops certainly weren't down to my lack of effort So, I decided to go back to basics and work on the soil and that meant a big delivery of cow manure. £30 for a huge trailer full one Autumn from the local farmer. And then also legume green manures for the future brassica and corn beds as well. What a difference. Not a sign of that "magnesium thingy".

Add some liberal dispensing of organic chicken manure pellets at 15Kg for £5 as and when required for all non root crops, especially 2 or 3 weeks before planting, and you'll be amazed at the difference. It only takes a year to turn it all around.

[RJR_38]

Thanks mum - I have to confess that I didn't really research Epsom salts I just assumed it wasn't organic.

In terms of general fertilisation - maybe you're right beesrus, the plot wasn't previously cultivated and all sorts of clearing and removal of junk had to be done. It is also surrounded by big trees which must leech out goodness. We do get a small manure delivery each year as a site but 4 barrows on a whole plot doesn't go far and as I have always put the spuds in the recently cleared bit (good weed cover and forced digging for me) so they have near had any. Sadly I can't get any more manure than this each year (long and boring story). I did give them a good feed of chicken pellets when they were first poking through but maybe I should give a mid season feed too. I have a green manure ready to plant once the spuds are up a well.

Thanks for this, lots to think about! 

[New shoot]

Give them some chicken pellets and then start composting like crazy (if you aren't already) 

On our site some of the worst plots are ones which were worked for years, then given up, but there never was a sign of a compost bin.  Now they are weed patches that get taken on by hopeful new newbies who often get disheartened and give up themselves.  As they clear the soil, you can see how pale and depleted it is, but as beesrus says, you can turn a plot around 

[azubah]

I spent years treating my tomatoes for magnesium deficiency until I noticed that if I gave them a general fertilizer it solved the problem. It was nitrogen they were lacking.

[Goosegirl]

I agree with many of the posts here, in that it can be difficult to distinguish between magnesium, manganeses and nitrogen deficiency. Perhaps googling images will help? Also try whay azuba did.

[JayG]

All fertilizers sold in the UK are required by law to list the micronutrients (trace elements) as well as the NPK values, so the labels on soluble feeds and solid fertilizers should show this information.

As ever, it's not quite that simple - my tub of Growmore doesn't list any micronutrients, so the assumption has to be there aren't any - my dried chicken poo doesn't list any either, but almost certainly does contain at least some given where it comes from, but being a 'natural' product it's perhaps not possible to guarantee the precise amounts. 

Miracle Grow and Phostrogen both list the micronutrients in full, so could be useful for those who can't or don't manure their soil regularly, and/or aren't sure whether or not their soil has a trace element deficiency.

[beesrus]

Interesting stuff JayG and pretty much spot on.
Let me give my opinion on chicken manure, as it isn't always possible to source big quantities of horse/cow  manure in your locale.
As it happens, my chicken pellets do list their constituent parts. A NPK of 4.5:3.4:2.7.... that's pretty good percentages given the bulk of manure compared to "fertilisers" On top of that is magnesium 1.1, calcium 9.3 and trace elements iron, boron, manganese, molydenum, copper and zinc.
My big mistake a long long time ago when I first started using chicken pellets was I was too tight with it, hardly surprising given the price you can pay for it in some places. I had almost assumed I should be sparing as if I were applying the chemical stuff. It doesn't have the huge quantities of vegetative matter of cow/horse manure, but one can't have everything.
The chicken manure I use from my local garden centre, Earlybird, is widely available online and reccomends quite a dose, some 300gms per square metre for thorough Autumn soil improvement, a little less for top dressings etc. In fact we should be using at least a whole 15kgm  bag on our plots every year. My plot is 200 square meters and I use a bag and a half per annum, along with green manures on certain beds. That is the most effective £10 I spend in a year on anything.  It really does make a huge difference.
It doesn't actually have the soil association stamp of approval, but then the Soil association allow far more chemicals under their banner than I would ever use on my plot. In fact, I don't knowingly use any chemicals apart from my pet friendly slug pellets that are deemed "organic".
Go get yourself some RJR, and be free with it. You'll see huge improvements.

[RJR_38]

Although I have been using chicken pellets and BFB when I put out plants (not spuds tho interestingly) I could definitely be much freer with it I think as I only use one large tub a year. £10 seems cheap though as I have been paying £7-8 for large bucket sized tub. I will look into that brand.

Everything else other than raspberries has been thriving but maybe this would explain why raspberries are a bit sulky as well.

I have a loose compost heap but had nothing from it yet. I want to get a bin but can't afford one at the moment.