Variable rate lime

We got some VR maps back this week for lime applications this autumn prior to drilling hybrid rye. A couple of fields missed getting lime last autumn due to poor weather conditions and as a result have an increased requirement this year. We've a few fields where sections require 3.5t/acre - 4t/acre. Are there any risks associated with applying this amount of lime in a single application? Normally we don't need to apply any more than 3t/acre and that was always what we had understood to be what is recommended as the max rate by the book....

ALA website suggests a split application on arable land for more than 3t/acre, before and after cultivating, but that is unlikely to be practical in our circumstances. We could potentially apply at the max rate suggested and grub it into the soil prior to plough.

We would prefer to crack on and get it done but if there are potentially any risks we would like to find out!
 
I would be loathe to apply more than 2 tonne or so in a single hit, I don't know your dirt but big doses in one go would be a bit unkind to soil chemistry in my wire. If you have historically applied 3 tonne in one go and had no issue then fine but apply the second extra hit later after working it in.

The risk would be in magically creating a serious trace element issue for your next crop as the top 'growing layer' would have a highly different pH in a localised layer.

You know your land better than anyone though. If it's acid as fudge, it's acid as fudge.
 
I wouldn't hesitate to throw it on! I have spread variable rate up to 4.5T/acre for customers with no problem. Choose a good soluble limestone with a range of particle sizes.
 
The risk would be in magically creating a serious trace element issue for your next crop as the top 'growing layer' would have a highly different pH in a localised layer.

That is what I had in my head but at the same time have found no evidence to back it up.

The contractor has spread 4t acre before on land he purchased with poor fertility and saw no ill effects. Our department of agriculture thinks the 3t/acre max rate was always an economic argument rather than having any effect on soil chemistry, but they're going to double check with their soil scientist. The soil mapping company says it's personal preference whether we want to whack it all on or split it.

It's just one of those things. The book says apply no more than 3t/acre but then when you start asking questions about why this is it is hard to get an answer. It's the chemical aspect I'm most intrigued by...
 

Shovelhands

Member
Location
Sunny Essex
Thanks for the tag @Phil P

I‘m not an expert in anything, so I won’t proclaim to know the science or the answers.

But I do know that I apply 4-5tpa regularly, and higher on occasion. That is fine ground limestone, but it’s ex water treatment works lime, so it’s a little different to a virgin ground limestone.
From the experience of my customers, they have no problems applying the higher rates. I remember applying 5tpa on a particularly bad part of a field, every year for five years! No issues....
I’m led to believe chalk is a bit different, but as I said I don’t know the science well enough to preach, or say what’s right and wrong.
 

Bogweevil

Member
It all depends - some boron and manganese deficiency might be a price worth paying to get the benefits of very heavy applications of lime quickly especially in climates/soils where opportunity to spread lime might be fleeting, particularly with pasture and low value broadacre crops. Growers of high value crops would be unlikely to allow pH to slip drastically, but would also be less willing to risk impairing crop performance and quality by heroic single lime applications.
 
If your ground regularly requires 3t/ac of lime and you’ve had no problems doing that in the past then I can see no harm in getting it done.

What concerns me more is that you say you’re going to get it spread before you plough. I really wouldn’t plough that amount down, preferring to put it on the top.

Ideally we'd plough and spread on top but we're in a high rainfall area and with such narrow weather windows we have to adapt sometimes. We find that unless conditions are perfect spreading on ploughed ground the lime spreader will leave compaction which is difficult to reverse. This field has missed getting lime in the last 2 autumn's because of difficult conditions. Open to suggestions about how to work it in better.
 

Yale

Member
Livestock Farmer
Ideally we'd plough and spread on top but we're in a high rainfall area and with such narrow weather windows we have to adapt sometimes. We find that unless conditions are perfect spreading on ploughed ground the lime spreader will leave compaction which is difficult to reverse. This field has missed getting lime in the last 2 autumn's because of difficult conditions. Open to suggestions about how to work it in better.
The way I see it is simple,if you plough lime under that is where it will stay.

Percolation of moisture/water will take any benefit down lower.

Ploughed under lime will do very little to rectify ph in the furrow layer.

You have to think whether it is worth spreading at all unless it is targeted where it is needed.

Just my opinion.
 
The way I see it is simple,if you plough lime under that is where it will stay.

Percolation of moisture/water will take any benefit down lower.

Ploughed under lime will do very little to rectify ph in the furrow layer.

You have to think whether it is worth spreading at all unless it is targeted where it is needed.

Just my opinion.

Yeah I appreciate that and I suppose that's where we thought the grubber would be suitable in this instance to work it well into the soil before the plough goes near it.
 
We plough but shallow - 6"-7" - any lime ploughed down will still be within reach of the plant roots and be ploughed back up and mixed through the profile within a couple of years? As @Cab-over Pete says, as it is ploughed the lime will get mixed through the profile anyay- nt as though we are completely inverting the furrow. Fed up of seeing lime spreader wheelings in the crop right through to combining.
 

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