Grassland Blog September 2022

Autumn nutrient management

Tom Oates, Nutrition Agronomist

A nutrient management plan that contains soil, tissue and organic manure sample results is essential. Grassland farmers should use an integrated approach to calculate crop nutrient requirements and nutrients provided by organic manures and manufactured fertilisers.

In England, it is a legal requirement to test fields once every five years. Therefore 20% of the farm should be soil tested each year. Good practice is to soil sample 25% of the farm each year, to improve monitoring of pH and P, K, Mg indexes and micro-nutrient content variability. Defra recommend taking soil samples in the autumn, which should be followed up with tissue/sward sample in the spring.

Grassland farmers take silage analysis samples each year to determine feed requirements throughout the winter, and it should be no different for grazing pastures. Taking tissue/sward samples is a great tool to help better determine in season fertiliser applications.

Management of slurry/swards

Remember closed periods for grassland in NVZ’s started on the 1st September on sandy or shallow soils and starts on the 15th October on all other soils, for applying high readily-available nitrogen organic manures for example whole digestate or cattle slurry. 

Consideration should be given for which fields will be used for first cut silage in the spring and the fields that from spring still need their potash application to balance the short fall of potash not applied in the spring to mitigate the risk of staggers. 

Aim to manage autumn grazing to protect the swards daughter tiller, therefore don’t graze swards past 4cm to encourage winter/early spring tiller development.


DIGEST-IT/slurry ammonia emissions

The conversion of nitrogen to ammonia in slurry happens during the following process:

  • Nitrogen is excreted by livestock both in the forms of urine and faeces. Most of the nitrogen in urine is present as urea and nitrogen in faeces is present in organic forms.
  • Hydrolysis, the process in which urea is broken down into ammonia and CO2, proceeds at a fast rate compared with mineralisation of nitrogen from the faeces, hence urine is generally the main source of ammonia emissions from livestock buildings.
  • Faeces contain the enzyme urease, therefore when urine and faeces come into contact, the conversion of urea in slurry into ammonia accelerates.

Microbial slurry inoculants, such as DIGEST-IT, provides a fermented microbial culture which microbes and dormant aerobic bacteria in the slurry feed on.

The microbes populate and break down the organic matter in slurry whilst also using ammonia gas as a source of nitrogen to grow, ultimately turning it into microbial nitrogen.

In summary the benefits of DIGEST-IT are:

  • Reduced volatilisation
  • Increased available N
  • Reduced crusting of slurry
  • Reduced odour

Need more detail?

Contact your Origin Fertiliser merchant or us directly by completing the form.