Variable rate N,P,K

[Banana Bar]

We have applied vra P and K for years although recently Biosolids and chicken manure has made it semi redundant. We have always used SOYL to sample and create pretty maps and then prepare a recommendation. Are others still using SOYL, anyone doing anything different.
VRA nitrogen has always looked interesting but there seem to be so many variables in the calculations I wonder how useful it currently is?


BB

 

[thorpe]

we went of soyl after the 2nd round of testing , result's were a bit iregular. + it was costing to much to pay a contractor to run over acres putting not lot on. we then bought our own spreader (contractor was most vocal about how we couldent justify it on our modest acrage, well feck him). anyway today we have a policy of feeding the crop not the soil

 

[snarling bee]

We have done VR P & K with SOYL for probably 25 years, not perfect but better than blanket spreading and ticks boxes. We now have more consistent indices, we use FYM, Compost and Biosolids so less relevant now.
I have tried VR N and agree that it is not really so clear cut. We don't do it only via manual controls if required. Never sure whether N should be applied King John or Robin Hood style. I don't believe in evening up crops using N either. I want every square m to produce at maximum economic level.. We try to produce an even crop with VR seed.

 

[warksfarmer]

We have applied vra P and K for years although recently Biosolids and chicken manure has made it semi redundant. We have always used SOYL to sample and create pretty maps and then prepare a recommendation. Are others still using SOYL, anyone doing anything different.
VRA nitrogen has always looked interesting but there seem to be so many variables in the calculations I wonder how useful it currently is?


BB

Started in 2006. Stopped in 2016. For me the technology isn’t there. When we variably applied N via an n-sensor our yields dropped. Yield maps prove this. I appreciate the way the n-sensor works today would be different to back then, but it’s still let down by the application equipment.

If you are wanting to variably apply liquid N over say a 36m boom then you need to be accurately sensing in 6m sections and then the sprayer needs to be able to vary the rate to those 6m sections. Cost effective technology doesn’t allow this so you end up altering the rate over the entire 36m and not in 6m increments or ideally even smaller.

The n-sensor or satellite image needs to be able to ‘sense’ in 6m or smaller increments, so basically you are splitting the field up into 6m strips or smaller.

As for spinning disc spreaders and variable N ………. don’t get me started as it just doesn’t work. If at 36m you’ve got 18m being dropped onto a single disc spinning at a set speed. Impossible to vary it accurately no matter what the manufacturer tells you.

It’s cheaper to blanket apply than invest in variable tech and apply variably last time I looked.

As for P & K then people need to question whether the crop actually needs it. RB209 is well out of date in my view and the index system needs flushing down the toilet.

I think variably applying lime has a place because this can be done in 1ha grid squares adequately.

We used soyl back in 2006 and still use them now because we are using the same point to take the soil sample today as we did in 06. But we aren’t variably applying anything.

 

[teslacoils]

Save the Dosh. Spend the extra on N.

 

[ollie989898]

Save the Dosh. Spend the extra on N.

And blanket the place the biosolids, FYM, digestate etc to suit P and K needs. There can't be many farms who genuinely need to buy in huge amounts of P or K these days given the amount of livestock or AD Units about.

 

[Brisel]

We have applied vra P and K for years although recently Biosolids and chicken manure has made it semi redundant. We have always used SOYL to sample and create pretty maps and then prepare a recommendation. Are others still using SOYL, anyone doing anything different.
VRA nitrogen has always looked interesting but there seem to be so many variables in the calculations I wonder how useful it currently is?


BB

I'm in the same situation as you. If you have the technology in place already, it could be useful for topping up the poor areas with P and K. VR N is and will be useful for canopy management in thick crops of osr but I have found it to be less responsive in cereals.

It seems to be proactive in seed rates rather than the reactive nature of VRN but yield maps still show the poor areas up despite this. You do get a more homogeneous ear count/m2 which should make the combine driver's life easier.

Are you thinking of SFI payments for precision applications?

 

[ollie989898]

The whole variable rate thing I always struggled to see a place for, it always seemed a high technology solution to a low technology problem to me.

 

[Sleepeasy]

How will the sfi variable rate payments work? Anyone got any ideas?

 

[Salopian_Will]

Variable Rate N with an N sensor works incredibly well on oilseed rape based on my one season’s use with one.

I’m not sure about wheat yet. Last March was horrendous for our wheat ground and nothing really got going with the exception of a few of our lighter fields. We didn’t have much flat wheat though, in a year where it was prevalent make of that what you will. I need to make better use of the algorithm modes for wheat that (within parameters) allows it to decide what amount of N to put on pretty independently.

It does require a lot of user input to get the most out of and unless you have a switched on operator, is better suited to owner operators.

 

[Salopian_Will]

The whole variable rate thing I always struggled to see a place for, it always seemed a high technology solution to a low technology problem to me.

Bought much £600t/fert recently? Soon focuses the mind.

 

[Brisel]

N Sensor needs a good operator. We had one on a farm I ran with an excellent pilot.

 

[Brisel]

The whole variable rate thing I always struggled to see a place for, it always seemed a high technology solution to a low technology problem to me.

It helps a newcomer understand the variations in soils

 

[T Hectares]

I use SOYL for VRA PK and lime, like many of the previous posters I see a bit less relevance now as we use more organic sources of P&K but I think it’s still useful to balance up the OM supplies
Definitely sensible for Lime

As for N I’ve tried it over the years and satellite based systems are tricky to get a meaningful timely reading from, cloud etc
N Sensor may be better but one of the biggest drivers of NUE for me is early front loading of Urea, by the time a decent NDVI image is obtained, most of the Urea is on meaning VRN is used to tweak for the final dose, by then the following weather is more important than a VRA which of course we have no control over !

I’ve started testing Grain but I think it’s going to take a period of time to build relevant data to work from, also with testing grain it’s a tiny percentage of the total crop so there’s probably going to be an inaccurate picture given from those samples, who knows, I’ll stay with VRA pk and lime with flat rate urea and keep looking at grain testing over the next few years

 

[T Hectares]

Bought much £600t/fert recently? Soon focuses the mind.

Buying £600/t N for that one season did focus my mind into targeting better NUE and lowering total rates, past experiences have left me sceptical to whether VRA would improve either of these factors

 

[Farma Parma]

Soilquest now RHIZA for Variable P&K&Lime either bulk or odd times calcifert
Its a no brainer you put it where the soil tested zones says it needs it
can you do any more better i doubt it?
Crops look fairly consistant too me.
Combine man says mine are v similar right across all fields, his own arnt quite the same.
He doesnt do bagged p&K tho. far more muck based mixed farming setup

Now ive never done any variable Nitrogen of any sort

But still hope too collect that £27/ha in addition to SFi later this year.
cant see any reason why not & then that makes the thing even more worthwhile.

 

[Salopian_Will]

Buying £600/t N for that one season did focus my mind into targeting better NUE and lowering total rates, past experiences have left me sceptical to whether VRA would improve either of these factors

Watching the N Sensor work in OSR which was hugely variable was an eye opener. We never normally put much N on (120-140 kgN typical) but in 2023 we had some very variable crops and it put nearer 180kg on the poor bits and around 100-130kg elsewhere. Probably ended up putting more N on than we have ever used previously but putting it where it was wanted accurately probably paid for the N sensor in one season (allowing for the FTEF Grant) on a relatively small area of OSR, albeit sold when prices were much better!

 

[T Hectares]

I used to have two 20ha fields side by side that would average similar yields and were a very similar soil type across them and were in the same crop each year
For a number of years I treated one flat rate and the other VRA seed & N

Nothing stood out on yield, nothing stood out visually in terms of evenness, head counts or ripening etc or on the margin
Similar overall amounts of Seed and N were used in both fields, I really lost enthusiasm with VR Seed and N apart from one block of land which had extreme variations in soil type between fertile loam valleys and thin steep chalk banks where Seed and N made a noticeable difference, so 20% of the farm showed a use where the other 80% didn’t, so different farms have different situations which may benefit more or less from my experiences