Milking platform stocking rate dilemma

News that the Department of Agriculture is planning to regulate the milking platform stocking rate has sent shivers down the spines of farm families operating higher than average milking platform stocking rates.

Until now, all stocking rate limits have been set at the holding level – that is the organic nitrogen excretion rate averaged across all hectares being farmed.

The first real break from this is coming this year, with any land farmed further than 30km away from the main holding not eligible for a derogation, unless the farmer can prove it is being intensively farmed.

Putting more focus on the milking platform stocking was mooted in the past, most notably at the last time the Nitrates Action Programme (NAP) was reviewed in 2021. However, it was never included as a measure in the final document at that time, but it is likely to be part of the next NAP.

What form any proposed measure is set to take remains to be seen, but the rationale for looking at milking platform stocking rate in the context of water quality is sound.

In a grazing context, the number of cows per hectare has a big impact on the level of inputs and indeed milk output per hectare.

Nitrogen use efficiency

The difference between the amount of nitrogen entering the farm in the form of feed and fertiliser and the amount of nitrogen leaving the farm in the form of milk, livestock sales and silage sales is called the nitrogen use efficiency or NUE for short.

Take two neighbouring dairy farms with 40 hectares as an example. One is stocked on the milking platform at 3 cows/ha while the other is stocked on the milking platform at 3.5 cows/ha.

Both have the same overall stocking rate because the higher stocked farm has more outside land, diluting the organic nitrogen produced by the extra cows.

Presuming grass growth is the same between the two farms, the higher stocked farm is likely to have a lower NUE and thus a greater risk of nitrogen being lost to the environment.

Urine splashes are a key source of N loss from grazing systems and the more cows there are per hectare, the greater the risk of N loss from urine splashes.

According to UCC researcher William Burchill, a typical urine splash contains between 500 and 1,000 units of nitrogen per splash and he says that about 30kg N/ha is lost annually through urine splashes. Now, it’s worth remembering that cows don’t actually produce nitrogen themselves, they simply recycle the nitrogen that they consume.

In other words, if cows are fed a grass only diet with no bought in feeds of any sort and where no nitrogen fertiliser is purchased, all the urine splashes and dung pads will be doing is recycling the nitrogen contained in the grass that the cows eat.

In such scenarios, the stocking rate argument is more or less irrelevant because additional cows are not adding to the amount of nitrogen in the system.

Of course, what tends to happen in practice is that the higher stocked farms tend to use more inputs such as purchased concentrate, more silage comes in from outside blocks and potentially more nitrogen fertiliser too.

Feeding higher levels of concentrate, zero grazing or feeding silage from outside blocks has the effect of enriching the urine splashes with higher nitrogen content on higher stocked farms. This is then deposited on the grazing block. With more cows per hectare, the risk of losses is greater when compared to the lower stocked farm, even if input per cow is the same.

Mitigation

In terms of mitigation, higher stocked farms need to ensure that they are recycling the nutrients produced by the cows back to the land area they originated from. This means that slurry needs to be targeted to the outside land.

Applying these nutrients back on to the milking platform accelerates the risk of nitrogen losses on these higher stocked farms.

Where slurry is going back to the outside land, the risk of nutrient losses from the higher stocking rates is abated.

By improving soil fertility and ensuring good swards of perennial ryegrass and white clover, these higher stocked farms can grow more pasture, thereby reducing the amount of imported feed required.

While the rules around milking platform stocking rate in the next NAP are yet to be worked out, farmers operating at higher stocking rates can expect greater scrutiny in the years ahead but where best practice is followed, a cut to cow numbers is unlikely.

Dilemma

The dilemma facing farmers that are running high stocking rates on the milking platform is that reducing the stocking rate can make the farm unviable.

For many farmers with smaller milking platforms, running a higher stocking rate is the difference between remaining as dairy farmers or going part-time farming with a different farm enterprise.

This is really evident in some parts of the country where the option to expand the milking platform and run a lower stocking rate is just not there. I’m thinking here of parts of west Cork where dairy farms are surrounded by either the sea or mountains or both.

If these farms are to have a future in dairy, they will need certainty that they can continue to farm while at the same time ensure that practices do not increase the risk of leaching.