Cymraeg

10: Soils and pollution

At the end of this session you will be able to:

  • Describe how important a healthy soil is to good farming
  • Explain the impact of slurry application rate on soil health
  • State the advantages of correct timing of application of slurry for economic reasons

How does slurry affect the soil?

A healthy soil will have:

  • A worm population of a minimum of 10 worms per square foot
  • Worms of various sizes to ensure replacements when old worms die
  • Healthy colour soil, without gleying
  • No sulphuric smell
  • Dee-reaching roots, that do not grow vertically down then start growing horizontally
  • Soil should be crumbly, and should break apart easily

Why is a healthy soil important?

Soil health should be maintained in order to:

  • Break down and utilise nutrients. If nutrients cannot be taken up by plants, fertilisers/FYM/ slurry will be wasted.
  • Avoid leaching nutrients. If soil is compact, roots will not be able to utilise nutrients and will leach with water into waterways.
  • Roots need to be able to grow deeply in order to utilise nutrients and also to reach water sources.
  • Increase grass/crop/plant growth, if roots are unable to work effectively beneath the surface, the crop will not grow as efficiently as possible.
  • Promote the growth of productive grass species, in a grassland, weed species are more likely to grow in compact, acidic and/or wet conditions.
  • Increase profits, when desirable species of grass/crops grow efficiently, maximising their potential yield, more crops are available to sell, or to feed livestock.

Healthy grassland soils pocketbook.

What effect does cow slurry have on the soil?

Farm management practices can both help and hinder the biological processes happening in the soil. Wherever possible farmers should seek to manage soil conditions to provide the best food and living conditions for soil organisms so that they can function in harmony and maintain fertile and productive soils.

Cow slurry contains a good source of Nitrogen, Phosphate and Potash.

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Application rate

  • Cow slurry should be applied at the correct rate.
  • The amount is measured in m cubed/hectare.
  • Farmers work out slurry application rate in litres/hectare.
  • However not all slurry is the same!

Variations in cow slurry

DM%- Dry Matter %.

This depends on the amount of water that mixes in with the slurry, and also the type of diet the cow is fed.

Type of Diet

The type of diet a cow is fed influences the amount of Nitrogen in the slurry – High N diet = High N slurry

Storage Method

What is the impact on the soil if too much slurry is spread?

Runoff causes a pollution risk

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Too much slurry can cause:

  • excessive contamination of the leaf blades in the sward
  • compaction of the already present dead and decaying material at the bottom of the grass plant
  • a sudden decrease in the pH of the topsoil, making the environment acidic
  • living organisms in the top soil to die
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Activity to check learning

Read the following extract from the AHDB leaflet on Healthy soils and create a diagram containing all the information.

In grassland soils, the soil life below ground often weighs ten times more than the grazing livestock you can see at the surface. Soil organisms are hugely diverse and play a range of critical roles in most soil processes. Soil biota is a collective term for all these living organisms, excluding plant roots, and is sometimes also simply called soil life.

In grassland systems, soil life:

  • Forms an intricate food web which gets energy from inputs of carbon to the soil in organic matter through plant roots, crop residues and livestock excreta;
  • Powers nitrogen fixation through the symbiosis between rhizobia and legumes;
  • Drives phosphorus, nitrogen and sulphur cycling to recycle nutrients back into a plant available form;
  • Stabilises soil structure and allows the soil to absorb intense rainfall through an open pore network;
  • Develops a sponge-like pore network to hold on to water and support pasture growth through drought.

Farm management practices can both help and hinder the biological processes happening in the soil. Wherever possible farmers should seek to manage soil conditions to provide the best food and living conditions for soil organisms so that they can function in harmony and maintain fertile and productive soils.

Life beneath your land

Activity: Draw a diagram to show the importance of soil life.

Summary

A healthy soil is vital to a healthy crop which leads to good farming.

Giving more thought on how manures are used and spread will lead to:

  • There are many ways to dispose of farmyard manure and slurry on the farm.
  • They all have the potential to damage the environment if not used correctly.
  • All the application methods have advantages and disadvantages.
  • The correct application rate at the correct time of the year is key to success.
  • The use of nutrient-rich organic farm waste will benefit the farm financially.

However, poor manure management can cause pollutants (including nutrients) to get into watercourses, lakes and groundwater, through runoff or drainage (for example, land drains).