Economically, slurry is a valuable asset. Teagasc estimates the value of nutrients in cattle slurry in 2024 with a dry matter (DM) content of 6% at €6.3/m3 (or €29/1,000 gallons) and pig slurry at 4% DM at €7.14/m3 (or €32/1,000 gallons).

Environmentally, slurry is a potential pollutant, particularly if applied at the wrong time or in the wrong conditions.

Teagasc reports that, if it reaches a watercourse, 1L of cattle slurry can be as damaging to aquatic life as 42.5L of raw domestic sewage, while one litre of pig slurry can be as damaging as 62.5 litres of raw domestic sewage.

For both of these reasons, it makes sense that slurry use is efficiently managed on Irish farms.

Slurry testing

Some of the simplest ways to maximise the gains from your slurry are to apply it in optimum conditions (a cool dull day when no heavy rain is forecast) and to test its composition and nutrient quality.

When combined with soil testing, understanding the composition of your slurry allows you to target the fields that will benefit from it most.

For example, silage ground can be targeted for slurry with higher potassium (K), whereas grazing swards, which typically have a lower requirement for phosphorous (P) and K, can be targeted with slurry with lower values of these nutrients.

Over the past two months, Footprint Farmers have been collecting slurry, soil and silage samples for laboratory analysis.

Combined, these results will offer important insights into how nutrients are cycling through their farm systems – from feed to slurry to crop and back to feed again – and help them to effectively target any deficits.

Silage results are in (see below) and we’ll be reporting in detail on slurry and soil test results from the Footprint Farms over the coming weeks.

Top tips on slurry testing

  • Slurry must be well agitated before sampling.
  • Take all necessary safety precautions when sampling – remember, a single breath of slurry gas can be fatal.
  • Test slurry from covered and uncovered tanks separately; slurry in covered tanks can have higher dry matter and twice as much nitrogen as slurry in uncovered tanks.
  • Slurry testing costs in the region of €85 for a basic NPK analysis, while more detailed micronutrient analysis costs around €135.
  • The same labs that carry out soil testing generally also test slurry.

    • For more on interpreting slurry test results, see here.

    For more on targeting your slurry spreading based on test results, see this article.

    Learn more: silage testing

    Maximising the efficiency of home-grown feed improves both economic and environmental sustainability. It can reduce reliance on costly feed imports, improve animal nutrition and performance, and means you can be more self-sufficient within your own farm gate.

    In terms of silage, every farm has different nutrient requirements and, therefore, the best results for one farming system may not be what suits another.

    However, generally, good silage tends to have the following characteristics:

  • Dry matter: 25% to 30%.
  • Energy: 11.5 to 12 ME (MJ/kg DM).
  • Crude protein: 14% to 16%.
  • Ammonia N (% of total N): 10% or lower.
  • pH: 3.8 to 4.2.

    • On Footprint Farms this year, silage test results for dry matter varied from 12.5% to 54.1%, crude protein from 12.5% to 18%, ammonia N (% of total N) from 2.6% to 13.9%, and pH from 4.4 to 5.4 (see Table 1, below).

    A wide range of variables, including weather conditions when cutting and ensiling, play a role in driving these results.

    However, knowledge of the characteristics of their silage has allowed Footprint Farmers to make informed feeding decisions over the winter months.

    For simple tips on how to improve your silage quality, read this article.