Soil Samples P question

Joe · Jan 9, 2017

I've taken over some ground that has been neglected to an extent for a good while, and just going through the soil samples today in preparation for the year ahead...
The results came back way better than I expected with lime requirements considerably less than expected especially when taking into account its a high MO area and reduction for such. Issue is P really, 13 of 20 plots index 4 for P & K and 1 plot Index 3 for both. The other 6 are Index 1 or 2 for P and Index 4 for K, question what is the best way to get the P up without applying K?

Novice question but is there an N / P fertiliser similar to 20-0-15 that can be used as never used one before like that before or would adding extra K matter?

neilo · Jan 9, 2017

TSP and straight N?
Or DAP (18:46:0) as a more expensive way.

hillman · Jan 9, 2017

Most of my ground is index 1 for P aswell joe
23-10-0 was what I was advised to spread , basically the n was nearly free when comparing to straight P

On the other side was advised also to spread calcium lime as ground very high in mag as always had used mag lime , as it was locking up the P and K in the soil

Anything different location wise in the low index plots ? What's the mag level etc ?

Joe · Jan 9, 2017

hillman said:
Most of my ground is index 1 for P aswell joe
23-10-0 was what I was advised to spread , basically the n was nearly free when comparing to straight P

On the other side was advised also to spread calcium lime as ground very high in mag as always had used mag lime , as it was locking up the P and K in the soil

Anything different location wise in the low index plots ? What's the mag level etc ?

9 of the plots need lime but only 1.5 t / acre, some are at 6.1 which is ideal here as right in middle of high MO area, mag levels are perfect & would always use Calcium lime here its the local lime. The six plots with low P all need lime, 1 would be the only 'stoney' field we have and other 5 would be maybe wet (far as could call any land here wet) part of the farm.
When I think of it now all are fields beside the river are the ones with low P, which would have flooded regularly over past years until it was dredged last year - if flooding would cause an issue?

neilo · Jan 9, 2017

Joe said:
9 of the plots need lime but only 1.5 t / acre, some are at 6.1 which is ideal here as right in middle of high MO area, mag levels are perfect & would always use Calcium lime here its the local lime. The six plots with low P all need lime, 1 would be the only 'stoney' field we have and other 5 would be maybe wet (far as could call any land here wet) part of the farm.
When I think of it now all are fields beside the river are the ones with low P, which would have flooded regularly over past years until it was dredged last year - if flooding would cause an issue?

Low pH will make the P less available, so liming will help with that side too.

milkloss · Jan 9, 2017

Does

neilo said:
Low pH will make the P less available, so liming will help with that side too.

Does the lab test take that into account when presenting the P figure?

gatepost · Jan 9, 2017

Are you going to graze only or is it all for mowing? would make a difference in what you put on and how much, also early cut silage will remove more than late cut hay. as @neilo says TSP is a good start. then how ever much N you think you need/production,

Joe · Jan 9, 2017

neilo said:
Low pH will make the P less available, so liming will help with that side too.

good point, all index 2 bar one plot so Lime defo way to go I think to get into 3.

Joe · Jan 9, 2017

gatepost said:
Are you going to graze only or is it all for mowing? would make a difference in what you put on and how much, also early cut silage will remove more than late cut hay. as @neilo says TSP is a good start. then how ever much N you think you need/production,

Graze only, 50 acres going to be reseeded outside of these plots and silage is targeted for current land.

Surgery · Jan 9, 2017

Not neglected too badly with indexs like you mentioned then

Joe · Jan 9, 2017

Surgery said:
Not neglected too badly with indexs like you mentioned then

Shows more the land quality than the maintenance tbh, some fields no lime or fertiliser outside of reseeding in my memory and newest lay would be 12 years old since beet production ended here. I don't remember some of the fields every being ploughed or reseeded, saying that some of the newer 12 to 15 year old lays have the worst results.

ollie989898 · Jan 9, 2017

TSP. Don't use DAP for reason of cost.

ollie989898 · Jan 9, 2017

It is better to correct P/K indices in individual applications I find, leaving your main Nitrogen dressing(s) alone.

Don't forget sulphur either.

Also, please do not lime or add P and K to anything solely on the basis that you are reseeding it and so you 'need' it. Apply manure/slurry by all means but please don't go down the old fashioned 'grass needs X and Y to establish'. That is bullocks.

In terms of nitrogen, I think around 80 units is the absolute max in my book for first cut, and then only on grass leys you know are in perfect condition else it won't be utilised properly- you don't put 101 octane juice in a Robin Reliant.

milkloss · Jan 9, 2017

What the latest on the ideal ph for grass establishment? Always aim for 6.5 here but I wonder if a little higher is better.

ollie989898 · Jan 9, 2017

milkloss said:
What the latest on the ideal ph for grass establishment? Always aim for 6.5 here but I wonder if a little higher is better.

I would be wary of trying to push pH values higher. Firstly, it costs money. Secondly, applying a lot of lime in a short space of time can seriously bugger the soil chemistry and cause all kinds of grief as various micronutrients are locked up. You have to recognise the kind of soil in your locality and where it naturally wants to be.

I have not seen any benefit from people applying more than 2 tonne/acre of lime in one go unless they are ploughing it down, and I don't like the idea of a heap of calcium being thrown on in one hit. Grass is more tolerant of various environmental constraints than we realise.

I don't have any land that is seriously acidic but I am told that trying to correct very acidic peaty soils is a massive can of worms.

Joe · Jan 9, 2017

ollie989898 said:
It is better to correct P/K indices in individual applications I find, leaving your main Nitrogen dressing(s) alone.

Don't forget sulphur either.

Also, please do not lime or add P and K to anything solely on the basis that you are reseeding it and so you 'need' it. Apply manure/slurry by all means but please don't go down the old fashioned 'grass needs X and Y to establish'. That is bullocks.

In terms of nitrogen, I think around 80 units is the absolute max in my book for first cut, and then only on grass leys you know are in perfect condition else it won't be utilised properly- you don't put 101 octane juice in a Robin Reliant.

Ye d I agree with this, so if P and K are ok in plot for reseeding or forage crop just go in with N?

Princess Pooper · Jan 9, 2017

Joe said:
I've taken over some ground that has been neglected to an extent for a good while, and just going through the soil samples today in preparation for the year ahead...
The results came back way better than I expected with lime requirements considerably less than expected especially when taking into account its a high MO area and reduction for such. Issue is P really, 13 of 20 plots index 4 for P & K and 1 plot Index 3 for both. The other 6 are Index 1 or 2 for P and Index 4 for K, question what is the best way to get the P up without applying K?

Novice question but is there an N / P fertiliser similar to 20-0-15 that can be used as never used one before like that before or would adding extra K matter?

Adding extra K is wasting money and likely to lead to high K values which increase the risk of staggers and milk fever. If you intend to spread muck or slurry in the future then that is higher in K as well so likely to create more of imbalance. I wouldn't be too up tight about the indices you have but I would go for some TSP on the index 1 land. Make sure you follow recommendations for your area/soils/cropping. We had the same issue on some heavy land, very high in Mg, but 0 and 1 for P. and a bit low on PH. Addressed pH first with lime and have been building the P gradually, make sure you make best use of slurry and manure, a good match with silage land which needs lots of K.

Joe · Jan 9, 2017

milkloss said:
What the latest on the ideal ph for grass establishment? Always aim for 6.5 here but I wonder if a little higher is better.

Would it not depend on land and location? Know ones here between 5.9 and 6.2 and advice given was no lime

Cab-over Pete · Jan 9, 2017

I realise I'm a bit biased, but recommending no lime on a 5.9 seems a bit daft.

I always recommend a good 6.5 for grass. I know, you're thinking "well you would say that", but it will start to drop after the initial couple of ideal years. It depends on budget too. It's better to do something rather than nothing and let the situation get worse.

Is pig slurry high in P? Don't know what makes me think that??

If you can spare the grazing withdrawal period, can you get some sewage sludge injected? I have a customer who does that on heavy clay grassland and it works a treat.

mezz · Jan 9, 2017

ollie989898 said:
TSP. Don't use DAP for reason of cost.

DAP worked out a lot cheaper per unit of P for us last year. Basically got the N for free and then some. I don't think there is any difference in the quality of P between the two types, so use which ever is cheapest on a unit basis (rather than per tonne).

DAP has now become the most popular source of P worldwide, as its supposedly easier and quicker to manufacture than TSP, so should be cheaper, but this will depend on the supplier. I understand it is also used as the raw ingredient for most compound fertilizers rather than TSP nowadays.

Soil Samples P question

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