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Top tips – Maximising the value of slurry

Top tips – Maximising the value of slurry

The value of fibre extends beyond the cow, with manure closing the loop in the fibre cycle. By focusing on fibre breakdown during this stage, as you can within the rumen, it is possible to improve utilisation and subsequently the value of on-farm manures.

This can make a major difference to your bottom line because manures are a highly valuable source of nutrients that can reduce the amount of purchased fertiliser you need. They also help increase soil organic matter (OM) which helps improve soil health and structure, both of which contribute to better crop performance.

Many of these benefits are linked to the fibre fraction within the slurry. So, to better utilise manures, the focus should be on breaking down the fibre at a molecular level to ensure the positive bacteria have a competitive advantage. If this happens, they will be able to use the sugars released by fibre breakdown, and the organic matter within the fibre is available to the soil and then the plant.

Fibre (cellulose, hemicellulose, and lignin) in the elemental sense is made up of long carbon chains (sugars), and the utilisation of the fibre is enhanced when these carbon chains are broken down through the correct treatment of the slurry. The benefits of enhanced fibre utilisation then continue into the next fibre cycle and highlights the value of attention to detail at all stages within the fibre journey on-farm.

Fibre breakdown in slurry during storage

The breakdown of fibre in the slurry during the storage phase is very important as it allows the carbon contained within the fibre to become part of the soil more rapidly and be taken up quicker by the plant once it’s been spread.

Throughout the natural composting cycle, various microbes, bacteria, enzymes and fungi work to break down the different parts of the slurry. This process starts with the components that are the easiest to break down, right through to the more complex parts, such as fibre.

The elements of slurry are broken down in this order:

  1. Sugars and dissolvable substrates
  2. Fats
  3. Fibre

Nutritional value of slurry and manure

Farmyard manure (FYM) can be a very valuable fertiliser that is cheap to use, however there can be major variation in nutrient levels. The quantity of purchased fertilisers that FYM can offset is therefore equally varied. To give some context to its value, below is a table which demonstrates the typical nutritional values that can be achieved by FYM.


Below is a scenario to showcase how much cost saving can be made from using slurry.


How to increase the nutritional value of slurry

Storing correctly

Making sure you have enough room to store your slurry for up to four months is important as it will offer:
• Flexibility to spread when conditions are right
• A maximised fertiliser value
• Reduced risk of water pollution
Aim to empty out your stores well ahead of winter so you have the maximum storage capacity over the winter period when spreading isn’t possible.
Carry out a thorough check of your store and patch any holes. Repairs should be completed well ahead of winter.

How to calculate how much slurry storage you will need

To calculate how much storage, you will need for your specific herd, visit this website: Booklet Fertiliser and Manure Plans – Part 2 Manure Planning

Water ratio of slurry

Slurry should have a ratio of 60:40 solids to liquid content so that it is at the right consistency for spreading. This means that extra water sometimes needs to be added but it’s important to note that too much liquid can cause the following problems:

  • Field run-off
  • Larger volume of slurry to spread which is costly
  • Diluted nutrient/fertiliser value

To avoid these problems, make sure that your slurry store is correctly covered so that excess rainwater can’t enter, and divert any run-off from nearby yards and buildings away from the store.

Enhancing fibre breakdown in slurry

Slurry treatments, such as SlurriN PRO, which contains specific enzymes can help breakdown the fibre in the slurry which allows more nutrients to be released and used by plants when the slurry is spread.


Benefits of using a slurry treatment

  • Creates a more stable slurry by promoting a positive fermentation process
  • Increases the quality of the slurry by reducing losses through negative fermentation
  • Organic nitrogen content is increased. This is because nitrogen is incorporated into the bacteria’s cells, reducing nitrogen leaching after the slurry is spread. This form of nitrogen is also rapidly available to the plant
  • The slurry is less prone to sedimentation and crust formation which improves the flowability of the slurry, reducing agitation time and making it easier to handle
  • Labour, machinery wear and tear and fuel costs reduce as the slurry is easier to spread


Reducing ammonia emissions with slurry treatment

When slurry is spread, a process called volatilisation can happen through a combination of microbial actions and predisposing environmental factors, which means that ammonium N (NH4+) is converted into ammonia (NH3) and is released into the atmosphere as a gas.

However, treating slurry with a biological inoculant can impact the nitrogen cycling in the slurry. Increasing the organic nitrogen content and total retained N by influencing microbial dynamics in the slurry which results in less ammonia production.

This is particularly important following pressure on the agriculture sector to reduce ammonia emissions.


Published Jan 3, 2022 | Updated Jul 4, 2023

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