P and K

Dave6170

Member
I have had a number of my fields all tested. They are mostly temporary grass with a couple of fields of barley rotated round.
Ph is good but P is very low and K is generally L to M+- and 3 are high K.

What levels of p and k am i aiming for in a grassland situation? And what are the best products to use to sort it out?
 

B'o'B

Member
Location
Rutland
I have had a number of my fields all tested. They are mostly temporary grass with a couple of fields of barley rotated round.
Ph is good but P is very low and K is generally L to M+- and 3 are high K.

What levels of p and k am i aiming for in a grassland situation? And what are the best products to use to sort it out?
I find if you test cold soils (November-March) you get low P results. Test the same field again in May/June for a free uplift of 1 or 2 indexes.
 

Dave6170

Member
These were sampled 10 or so days ago when the weather was really mild and dry. Would that make much difference?.

Most of them have all been tested in the past few years for ph and p was low then too. Finally have ph correct so want p and k sorted now.
 

B'o'B

Member
Location
Rutland
These were sampled 10 or so days ago when the weather was really mild and dry. Would that make much difference?.

Most of them have all been tested in the past few years for ph and p was low then too. Finally have ph correct so want p and k sorted now.
Yes soils are cool enough for P index to drop.
What time of year were your last samples taken?
If I was a fert salesmen offering soil testing I’d do all I could to sample over winter.
As for products I’d look at Fibrophos/Tiger as a start and see how they stack up for you. There are currently a couple of threads already going for you to have a good read through.
 

Dave6170

Member
Yes soils are cool enough for P index to drop.
What time of year were your last samples taken?
If I was a fert salesmen offering soil testing I’d do all I could to sample over winter.
As for products I’d look at Fibrophos/Tiger as a start and see how they stack up for you. There are currently a couple of threads already going for you to have a good read through.
Probably summer time, before i ploughed and reseeded.

Yes i have been following them.
Fibrophos was 140/t here last time i priced it?
 

Chae1

Member
Location
Aberdeenshire
I have had a number of my fields all tested. They are mostly temporary grass with a couple of fields of barley rotated round.
Ph is good but P is very low and K is generally L to M+- and 3 are high K.

What levels of p and k am i aiming for in a grassland situation? And what are the best products to use to sort it out?
Muck/slurry.

Or fibrophos.

After silage how much K do you put on to replace offtake?

How much bagged p&k do you put on spring barley ?
 

Dave6170

Member
Muck and 125kg/ha of the same silage fertiliser. If no muck 125kg/ha of 0 0 60.

All reseeds get 1 27 0.

Barley fields get muck and 250kg/ha 10 26 26 down the spout.
 
You will not get a difference in soil test results regardless of the time of year they are done or the temperature of the soil/air. It is true that the availability of soil phosphate to plants varies with temperature, but that won't fool a mass spectrometer: it's either there or it isn't. That assumes of course you are sending the soil to a lab that actually uses a mass spectrometer.

I used to do soil samples all year round virtually, a LOT are done immediately post harvest for obvious reasons.

How many acres are we talking and what were the results as indices? Very low P needs sorting, TSP is the usual weapon of choice for that, but you could use another product if the K was low as well.

Slurry/muck should be targeted on to fields with recognised issues, use it to replace the K removed with grass crops.

If the area is large enough then fibrophos might be worth using, don't go mad with it on fields already high with K though as you won't see a return on that.

EDIT: your careful use of 0.0.60 is probably what is holding the K values up. You could probably buy in a few bags of TSP and use 250kg/ha of that to bring the worst fields right on P.
 
250 odd acres. Only 25ac of this is barley.

Local fert guys dont recommend tsp. They say scotphos is a better product. I dont know enough about them
I have no idea what scotphos is but I am happy using known and reputable products. Any kind of branded fertiliser product I become automatically suspicious of.

I don't know what your land is like or what your weather will do but if you get the opportunity to get stuff on in the next month, I would get going with the P and K as soon as practical. The grass will start looking for it once it begins to grow. Nitrogen of course is different.

Correct what you need to correct or what you can justify economically this year, take note of how the grass goes this season and perhaps resample in a couple of years.

In most of my area the P was often low, not massively so, but usually it was low, high K, tonnes of magnesium and the pH was acceptable. I could not quantify how much this low P situation was losing people in terms of grass growth but you could spot the fields that were happy very readily.
 

Dave6170

Member
I have no idea what scotphos is but I am happy using known and reputable products. Any kind of branded fertiliser product I become automatically suspicious of.

I don't know what your land is like or what your weather will do but if you get the opportunity to get stuff on in the next month, I would get going with the P and K as soon as practical. The grass will start looking for it once it begins to grow. Nitrogen of course is different.

Correct what you need to correct or what you can justify economically this year, take note of how the grass goes this season and perhaps resample in a couple of years.

In most of my area the P was often low, not massively so, but usually it was low, high K, tonnes of magnesium and the pH was acceptable. I could not quantify how much this low P situation was losing people in terms of grass growth but you could spot the fields that were happy very readily.
http://www.originfertilisers.co.uk/products/gafsa-p-and-pk

Used to be called scotphos years ago. Its 1 27 0
 

B'o'B

Member
Location
Rutland
You will not get a difference in soil test results regardless of the time of year they are done or the temperature of the soil/air. It is true that the availability of soil phosphate to plants varies with temperature, but that won't fool a mass spectrometer: it's either there or it isn't. That assumes of course you are sending the soil to a lab that actually uses a mass spectrometer.

I used to do soil samples all year round virtually, a LOT are done immediately post harvest for obvious reasons.

How many acres are we talking and what were the results as indices? Very low P needs sorting, TSP is the usual weapon of choice for that, but you could use another product if the K was low as well.

Slurry/muck should be targeted on to fields with recognised issues, use it to replace the K removed with grass crops.

If the area is large enough then fibrophos might be worth using, don't go mad with it on fields already high with K though as you won't see a return on that.

EDIT: your careful use of 0.0.60 is probably what is holding the K values up. You could probably buy in a few bags of TSP and use 250kg/ha of that to bring the worst fields right on P.
Where do you send samples for mass spectrometry analysis?
As far as I was aware all UK labs as standard did the DEFRA approved method which I think is Olsen P.
I doubt results from mass spectrometry results would fit into the indexes in RB209 (even if they are more accurate).
 
For every person who says don’t sample soils when it’s wet and cold, you’ll get somebody else saying don’t sample whilst it’s warm and dry.

Which all makes my theory work quite well. Sample when soils are moist and friable with a growing crop. But then try organising farmers to make up their mind at the right time of year!!

In reality, farmers will usually find some way or other to grumble about poor sample results!
 

B'o'B

Member
Location
Rutland
For every person who says don’t sample soils when it’s wet and cold, you’ll get somebody else saying don’t sample whilst it’s warm and dry.

Which all makes my theory work quite well. Sample when soils are moist and friable with a growing crop. But then try organising farmers to make up their mind at the right time of year!!

In reality, farmers will usually find some way or other to grumble about poor sample results!
I’ve taken all the soil samples myself so I’m not trying to pin the blame on anyone else. Just reporting what I have experienced.
 

neilo

Member
Location
Montgomeryshire
Surely more important to always sample at around the same time of year, to make results comparable?
I’ve always been led to believe that P&K levels will show a bit lower in mid-winter and higher in summer. Just take that into account in the ‘ishness of the results perhaps? It’s certainly not an exact science anyway.
 

B'o'B

Member
Location
Rutland
Surely more important to always sample at around the same time of year, to make results comparable?
I’ve always been led to believe that P&K levels will show a bit lower in mid-winter and higher in summer. Just take that into account in the ‘ishness of the results perhaps? It’s certainly not an exact science anyway.
I think you’re right, the trouble is RB209 doesn’t take it into account. P seems to vary more than K in my experience.
 
Where do you send samples for mass spectrometry analysis?
As far as I was aware all UK labs as standard did the DEFRA approved method which I think is Olsen P.
I doubt results from mass spectrometry results would fit into the indexes in RB209 (even if they are more accurate).
Yara use inductively coupled mass spectrometers, I have seen them with my own eyes, and they are needed because they are often asked to provide all kinds of data on soil samples, testing for heavy metals and so forth, the chap in charge explained that with their equipment they can test for anything in a sample right up to the really heavy elements like uranium. I guess using wet chemistry constantly to test thousands of soil samples and aiming to deliver a broad spectrum test with a dozen measurements for each just isn't possible in the required timeframe and cost.

I have asked them the exact same question myself. I also asked if it mattered what form nutrients may be in, along with the question of can soil samples be too wet for them to analyse and was told it didn't make any difference. The whole lot gets put into an oven before getting anywhere near any analysis equipment and is then ground literally into dust, I presume leaving a lot of stones in the sample might then cronk your results. I guess the same may be true of leaving any kind of extraneous organic matter in there. The bit I am not so sure of is how they get from a pile of dust, a solid form, into a liquid form that is then pumped into the mass spectrometer. It was explained at the time but I can't remember.

A significant portion of the work they do is done in the summer, prior to other crops being planted.
 

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