Storing, moving and documenting organic manure

Slurry, solid manure, liquid manure and digestate are all subject to three sets of rules at once, each asking a different question. Fertiliser law asks whether you have enough storage space, so that you're never forced to spread at the wrong time. It also asks where the material goes, or where it came from, the moment it changes farms. And water law asks whether the tank is leak-proof and being monitored.

The three questions have different audiences. Storage capacity is of interest to the agricultural authority, the transfer concerns sender and recipient jointly, and installation safety falls under the water authority. No single document can cover all of that, and an inspection usually checks only one of the three trails at a time – but it checks that one thoroughly.

Storage space is either built or it isn't – that's how the farm sees it. The authority sees it differently: it asks about the usable capacity, and that is smaller than the built volume. Freeboard, residual quantities that can't be technically pumped out, and the share added by rainfall are all deducted. Handing over the construction drawing hasn't answered the question yet.

Then there's composition: solid and liquid organic manure are assessed separately, and material received from elsewhere counts too. A farm that regularly takes on digestate from a biogas plant needs capacity for quantities it never produced itself.

In practice that means: capacity belongs on record as a figure, per storage site, with type and physical state – not as a rule of thumb in the farm manager's head. Kept that way, you can answer a query in the same minute it's asked.

Whenever organic manure leaves the farm or arrives on it, a record-keeping duty is triggered – on both sides. The sending farm records what it handed over, the receiving farm what it took in. This is exactly where things break down most often in practice: one side has the paperwork, the other is counting on it turning up eventually.

At the core of the record are the holding numbers of both parties. A name isn't enough, because the authority has to be able to cross-check the two records against each other. That also means date, type of material, quantity and the nutrients it contains – nitrogen and phosphate are the whole reason the transfer gets recorded in the first place. Anyone delivering across a state border has additional reporting channels to observe.

If a field lies in a nitrate-vulnerable zone, extra requirements apply – including for material that's received. The zone map isn't set by the federal government but by the individual Bundesland, and it gets updated. A field can be affected in one farming year and not the next.

For the record, that means two things. First, the classification isn't a permanent state but a dated figure – anyone documenting it should note which official data set they relied on. Second, the neighbour's word is worthless: what counts is your own Bundesland's map for the current farming year.

A slurry tank is legally an installation for handling substances hazardous to water. That makes it subject to a separate set of rules that has nothing to do with fertiliser law: it has to be leak-proof, it gets inspected at recurring intervals by a qualified expert, and the farm itself checks it regularly. Work on such installations is reserved for certified specialist companies.

How strict the requirements are doesn't depend on the tank alone, but on its location. More applies in a water protection area or a flood zone than elsewhere, and the water hazard class of the stored substance shifts the threshold further still.

The in-house inspection is the part that's easiest to let slip – it costs little time, but only produces evidence if it's written down. A date remembered in someone's head is not a record.

It's noticeably rare for a wrong quantity to be the cause. It's the missing other side of a transfer, a capacity figure nobody can derive, and an in-house inspection that happened but isn't written down anywhere. All three are gaps in the documentation, not technical mistakes – and none of the three can be fixed after the fact.

The most effective step is therefore unspectacular: record every event where it happens, with the same details the other side is keeping too. Then the paperwork is already done by the time anyone wants to see it.