Soil test

[glensman]

Just got soil tests back on a field I'm reseeding. We are a hill farm so land is average quality, the field has been cut once a year for silage and had a coat of manure (sheep bedding) afterwards for the last 5 or 6 years. The results are as follows.
Ph 5.8 guideline 6.0 slightly low
Phosphorus 18 guideline 16 normal
Potassium 90 guideline 121 low
Magnesium 232 guideline 51 very high

Why would the magnesium be so high and what effect would that have on grass coupled with low potassium?

 

[Derrick Hughes]

Have you put anything else back on to replace the potash removal

 

[glensman]

Have you put anything else back on to replace the potash removal

Just the manure (1 year old)

 

[Sir loin]

look at the thread
I asked the same question

Magnesium locking up potash?

I have a field with a high mg index (5.3) and moderate k (1.7) ph 6.1, it's fairly heavy land but last year it just didn't perform the grass was kinda yellowy and next to no yield compared to other fields. It was reseeded in 2011. now the yara rep tells me to put potash on ( he would) but I...

thefarmingforum.co.uk

 

[Derrick Hughes]

Just the manure (1 year old)

That's why your potash is low

 

[Wombat]

Just got soil tests back on a field I'm reseeding. We are a hill farm so land is average quality, the field has been cut once a year for silage and had a coat of manure (sheep bedding) afterwards for the last 5 or 6 years. The results are as follows.
Ph 5.8 guideline 6.0 slightly low
Phosphorus 18 guideline 16 normal
Potassium 90 guideline 121 low
Magnesium 232 guideline 51 very high

Why would the magnesium be so high and what effect would that have on grass coupled with low potassium?

Magnesium is normally a characteristics of how heavy and sticky the soil is.

Most of ours are 800 plus so i wouldn't worry about 252

 

[Sheep]

How many tons of manure have you put on?

 

[Renaultman]

That's why your potash is low

Or because the magnesium is locking the potash up, I'm only a very amateur chemist but calcium lime will help

 

[upnortheast]

High mag is common in the UK. 2 tonne acre calcium lime would bring your pH up. Muriate of potash would help the k level. It's 60% so 50 kg acre every year

 

[Derrick Hughes]

Those mag levels are not massively high , but Gypsum is commonly used in high mag soils that will help In nutrient lock up, but if bigger concern is the low K level that is common when fields are cut every year, low potash levels also make the forage more prone to drought

 

[glensman]

How many tons of manure have you put on?

I'd only be able to guess at that, what would you consider to be the correct tonnage per acre.

 

[Derrick Hughes]

I'd only be able to guess at that, what would you consider to be the correct tonnage per acre.

You will never replace your potash off take with a bit of sheep dung

 

[upnortheast]

I'd only be able to guess at that, what would you consider to be the correct tonnage per acre.

Depends on the type of muck. I would guess your "sheep bedding" is not as high in nutrients as (for example ) dairy cow muck

 

[glensman]

You will never replace your potash off take with a bit of sheep dung

It was a bit of an experiment

 

[Lazy Eric]

Do you apply any bagged fertiliser in spring before you cut it?

 

[Derrick Hughes]

It was a bit of an experiment

I'm all for that

 

[glensman]

Do you apply any bagged fertiliser in spring before you cut it?

Yes, it was getting about 100kgs per acre of 20 10 10 (2 bags)

 

[upnortheast]

Lot depends on how much production you are aiming for
Because your P is OK I would go for equal amounts of N & K Probably not a compound that does that so 2 bags nitram or similar & 1 bag MOP

 

[Bald n Grumpy]

Magnesium levels here not quite as high as yours but been advised recently that they could be interfering with potash up take. Looking into using gypsum probably in liquid form put on with a sprayer. Supposed to help with compaction and cultivations as well

 

[Yale]

I looked into gypsum and chatted to a supplier.

They reckoned you needed something like 5t/acre to make much of a difference.

And they no longer supplied it.