Documenting fertiliser requirement – what's required, and in what order

The fertiliser requirement assessment and the fertilisation record are two separate documents with two separate purposes. The requirement assessment is a forecast: it answers how much nitrogen and phosphate a given crop on a given field actually needs this year. It is produced before the first fertiliser application and forms the ceiling for everything that comes after.

The record is a log: it captures what was actually spread – when, on which field, what material, what quantity, what nutrient content. In Germany, both documents are kept per field or management unit, not per farm.

The most common mistake isn't a wrong figure – it's a missing document: the application is logged in the tractor terminal, but the requirement assessment exists only as a thought, or as a scrap of paper nobody can find any more.

A requirement assessment produced after fertilising no longer serves its purpose – it is meant to bound the decision, not justify it afterwards. This is exactly what inspectors check: if the calculation's creation date falls after the application date, the Fertilization Ordinance's duty is formally breached, even if the quantities themselves are perfectly correct.

In practice that means the requirement assessment belongs in winter or early-spring planning, not in the rush of the season. Keeping it digitally gets you the timestamp automatically – without having to rely on nobody ever questioning a handwritten date later.

The requirement assessment isn't just a lookup table by crop. Among other things, it factors in the targeted yield, the previous crop, organic fertiliser applied the year before, humus content and soil-test results. Every one of these figures is an assumption that has to be justifiable.

That's why traceability matters more than precision to the second decimal place: being able to show where a yield target comes from puts you in a stronger position than quoting a very precise figure with no traceable origin. Soil tests are valid only for a limited time, and only for the field they were taken from – not for the field next door.

Fields in nitrate-vulnerable or eutrophied zones – colloquially “red” and “yellow” zones – are subject to extra requirements that go beyond the general rules. In Germany, these zones are designated by the individual Länder and can change; a field can be affected in one year and not the next.

This is the point where one-size-fits-all guides stop being useful: which condition specifically applies to your field is set out in your Bundesland's own fertilisation ordinance, not in the federal ordinance alone. Check the zone designation afresh every farming year, rather than relying on the year before last.

In our experience from talking to farms, it's rarely the limit values that trip people up. It's gaps in the chain: an application that only ever sat in the spreader's terminal and never made it into the farm's own documentation. A field that was swapped without the management unit being updated to match. A nutrient content carried over from an old analysis, even though the batch of slurry is long since a different one.

These mistakes don't come from carelessness – they come from documentation being separated from the work in both time and place. Catching up on it at the office computer in the evening loses detail, and never catching up on it at all leaves a gap nobody can reconstruct later.