Five thousand cattle produce a lot of slurry and cattle on a finishing diet produce high dry matter slurry that is high in phosphorus (P) and potassium (K).

On the Kepak farm in Clonee, Co Meath, that slurry is fuel for the crops that are grown. Seventy per cent of the feed in the animals’ diets on the farm is grown on the farm whether that be maize, barley or wheaten straw.

Sam Myles is the farm manager at Kepak and he’s made many changes in recent years.

Partnering up with Teagasc on the Signpost Programme has helped with this as measurements and chats with a wider team help to reaffirm some decisions. For example, from adding to the crop rotation to planting cover crops, nitrogen efficiency has been improved.

In early March, Kepak held a farm walk with Teagasc and managing slurry was a key part of this walk.

The farm is 314ha in size and all land is within an 8km radius of the farmyard. It’s heavy land.

A high clay loam provides great strength to grow crops, winter wheat hits 5t/ac and winter barley averages 4t/ac, but heavy soil also comes with risk of phosphorus loss, so this is something that needs to be considered.

Slurry is applied to growing crops. This crop of winter wheat received 3,000 gallons/ac of cattle slurry.

The farm produces more slurry than it needs and neighbouring tillage farms take in exports from the farm. This means that the farm’s stocking rate remains below 170kg N/ha.

No more P and K purchased

Soil samples are taken every three years and with a lot of access to organic manure it is no surprise that P and K levels on the farm are excellent.

The farm has high soil pH levels (over 7), so there is a P allowance for cereal crops on the farm.

However, Teagasc soils specialist Veronica Nyhan said it may not be a bad idea to leave out phosphorus for a year or two to try and get the index back to 3 and optimum levels for availability and water quality. Slurry is tested on the farm.

The spreader works at 12m so needs to drive on the crop every second run.

It is generally high in dry matter and as an example some of the slurry tested this year was at 16-7-15 for N-P-K per 1,000 gallons at 8% dry matter. This compares to the Teagasc standard and what needs to be used in a nutrient management plan of 9-5-32 for cattle slurry at 6% dry matter.

Teagasc’s John Mahon and Veronica Nyhan encouraged the 70 or so in attendance at the farm walk to at least test their slurry with a hydrometer. This will give the dry matter percentage. If the dry matter is low, then the N, P and K levels are not going to be as high as the 9-5-32 outlined.

The spring barley ground will get 2,500 gallons of this slurry delivering 41 units of nitrogen (N)/ac, 18 units of P/ac and 62 units of K/ac. This will fulfil the P allowance, almost fill the K allowance and leave just 100 units of N from artificial fertiliser to be applied per acre.

Phosphorus loss is an issue on the heavy clay soils on the farm. This 3m buffer should help to reduce this loss in the wet. \ Barry Cronin

During the crop walk, a demonstration was carried out of slurry being spread on to a growing crop of winter wheat.

The winter wheat had not received any fertiliser or slurry up to now, but 3,000 gallons/ac were applied equating to 48 units of N, 21 units of P and 72 units of K per acre.

Key to slurry use on the farm is applying in the springtime, either to stubbles with low-emissions slurry spreading (LESS) equipment and incorporating that slurry within 24 hours or by applying to a standing winter crop in the springtime.

Some of the crowd at the Teagasc Signpost Farm walk on Kepak's tilllage farm in Clonee, Co Meath. \ Barry Cronin

No compound fertiliser has been purchased on the farm for the past two years.

The slurry was spread using an umbilical system with a flow meter to ensure that the right rate was being applied. The system was spreading at a width of 12m.

Tramlines are 24m, so the tractor needs to drive on the crop every second run. Teagasc adviser Conor O’Callaghan estimated that driving on the crop results in a yield loss of 0.1t/ac to 0.2t/ac.

Nitrogen use cut

Nitrogen use on the farm has been cut. For example, artificial nitrogen use has been reduced by 50kg/ha on the farm’s winter wheat. This is due to a number of factors.

A switch to protected urea from CAN is hoped to reduce emissions, as well as reduce nitrogen rates.

The organic manures mentioned above are contributing nitrogen, but also improving soil health.

Crop rotation has also helped to improve soil health and reduce N requirement. Oilseed rape and beans are the break crops of the rotation.

Cover crops

Cover crops have been a big help to improve soil health and structure.

As evidenced from the ponds of water lying in the fields, it is land that needs some care.

Cover crops were grown on the farm for the first time in 2021. It was a crop of oats and the seed was spread with the Bredal spreader. In 2022, a crop of leafy turnip and forage rape was planted.

Last year, the cover crop was planted on the August bank holiday weekend, leafy turnip and forage rape again, and Teagasc measured the crop nitrogen uptake.

Some 40kg N/ha had been taken up by that crop, so this allowed artificial nitrogen rates to be pulled back.

Sam has noticed the level of biodiversity increase in the soil in those short few years.

The stock on the farm are too heavy to graze and are only there for 90 days to be finished.

As it’s a tillage farm, there is no fencing infrastructure on the farm, so Sam hasn’t considered bringing sheep in to graze the cover crops.

Some straw is chopped on the farm, but the finishing unit has high demand for straw, so chopping is generally limited to headlands and other areas which need some help to try to improve soil structure.

In autumn 2023, Sam noted that 40ha of winter oilseed rape were planted.

They didn’t manage to get any winter barley planted.

Some 60ha of winter wheat went in after maize. With poor conditions, the decision was made to opt for spring cereals and of course maize for silage. Maize is all grown under film.

The land on the farm is very heavy and prone to flooding. \ Barry Cronin

Water quality

The improved nitrogen efficiency on the farm, along with cover crops to soak up nitrogen, are a help to water quality. However, nitrogen is not the real concern on this farm.

Phosphorus is the bigger risk of loss on this clay soil. Phosphorus attaches itself to soil particles and moves into watercourses in sediment.

To prevent or reduce this loss, and of course to adhere to conditionality (cross compliance) under CAP and nitrates regulations, the farm has 3m grass buffers beside watercourses.

A Timothy and Cocksfoot margin has been planted to prevent soil and phosphorus leaking into water. Where maize is planted, 6m needs to be left as it is a late-harvested crop.

Very importantly, it was pointed out that slurry should not be applied within 5m of a watercourse and in the first and last two weeks of the spreading season this buffer extends to 10m.