Attachments“With slurry, you can fertilise with preci­sion”

The strict legis­la­tion on fertil­ising with slurry is causing quite a stink for many farmers. Farmer Stefan Vogel­sang explains why it’s still useful and how it can be done without stress.

Stefan Vogel­sang heads one of the Water Frame­work Directive‘s 31 model enter­prises in North Rhine-West­phalia which test inno­v­a­tive tech­niques to advance farming, protect ground­water and use fertiliser more spar­ingly and effi­ciently.

Mr Vogel­sang, what role does slurry play in your enterprise’s fertiliser plan­ning?

Slurry is impor­tant because it is a compound biolog­ical fertiliser. I use it for its vast range of nutri­ents as well as to achieve a circular economy on the farm: The animals turn what I feed them into excre­ment and this then goes onto the field, thereby going back into the cycle.

There’s a lot of talk about slurry. When it comes to slurry and plan­ning fertiliser require­ments, what do you need to keep in mind?

Slurry has a bad repu­ta­tion, and wrong­fully so. With slurry, you can fertilise with preci­sion and deter­mine nutri­ents. As farmers, we typi­cally do this by first stir­ring up the slurry and taking a sample, which a lab then analyses to find out its exact makeup. This is the foun­da­tion for plan­ning fertiliser require­ments. There are many factors to consider: Average yields, soil types, which crops we grow, crop rota­tion, catch crops and more. We calcu­late all of this which then allows us to deter­mine the fertiliser require­ment. And this fertiliser require­ment is the legal upper limit which we’re not allowed to exceed.

Stefan Vogel­sang manages one of 31 Water Frame­work Direc­tive model farms in North Rhine-West­phalia.

How does this slurry analysis usually work?

It’s really impor­tant to obtain a repre­sen­ta­tive sample of the slurry. The lab only analyses half a litre of slurry which needs to repre­sent the four million litres of slurry that are in my storage tanks. That means I need to stir up the slurry very well to make sure the liquid is evenly mixed so we get a repre­sen­ta­tive sample. The sample gets sent to the lab and I get the results 10 days later.

That sounds like a lot of work. Is there another way?

HarvestLab 3000

Near-infrared (NIR) spec­troscopy to analyze various constituents within harvested crops, silage or slurry (one sensor, three appli­ca­tions)

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Yes, there is a better way. We’ve been using the HarvestLab™ 3000 NIR sensor in our busi­ness for the past five years; this allows us to analyse our slurry in real time. This saves us from having to stir it up in advance: If I want to spread slurry, I don’t have to stir it up 10 days in advance, take a sample wait for the results. I can stir up my slurry just before taking it to the field, eval­uate it there and spread it according to the nutri­ents it contains, thus ensuring consis­tent crops across the board.

How does the sensor work?

A pump takes in the slurry and pushes it along through a pres­sure line, where it passes the sensor and into the spreading device at the rear. The sensor eval­u­ates the makeup of slurry in real time during spreading. The sensor is connected to an ISOBUS wiring harness. This lets me see the data trans­mitted by the sensor on the terminal right in front of me in the tractor cab. I can enter a target value there which is what the slurry drum needs to work towards. The HarvestLab™ 3000 controls this value auto­mat­i­cally.

The sensor of the HarvestLab™ 3000 measures the nutrient concen­tra­tion live during appli­ca­tion.

So you have your own on-board lab with you at all times and know exactly which nutri­ents and how much of them the slurry contains. Does this benefit only your busi­ness?

We also supply slurry to arable farming enter­prises. This is bene­fi­cial for them because we can docu­ment every­thing in detail when we spread slurry for them. We have an overview of the nutri­ents in the Oper­a­tions Centre and after the work is done, we can create a printout showing which nutri­ents were applied and how much on certain days. We can report this directly in the online data­base, meaning we are in compli­ance with the law straight away. This also lets farmers check if they have actu­ally received the nutri­ents that they ordered.