Fertiliser Planning for the Growing Season

Fertiliser prices are at an all time high and farmers are asking what can be done to help reduce fertiliser costs on their farm?  Take time now, before the growing season starts to carefully consider how you can make best use of slurry and manure available on your farm.  By doing this you can reduce your fertiliser bill and maximise grass production.

There are three essential steps that need to be considered:

Soil analysis measures the amount of available nutrients in the soil, and is the basis for making accurate decisions on slurry/manure and fertiliser applications.  Samples should be taken before any slurry or fertiliser is applied therefore samples should be taken as soon as possible.  A soil analysis report will give the pH, that is,  the lime requirement, and the available amounts of phosphorus (P), potassium (K), and magnesium (Mg) in the soil.  For farmers applying for the Nitrates Directive Derogation it is important to note that every four hectares needs to be soil sampled every four years.

Sampling augers and bags are available from your local DARD Agricultural Development Centre.

Slurry and manure are valuable resources that should be used wisely to maximise grass production without endangering the environment.

Every 9,000 litres (2,000 gallons) of dairy cow slurry can supply up to 9.5KG nitrogen, 11KG phosphorus and 31KG potash.  At today’s fertiliser prices this slurry has a nutrient value of between £25-30.  By multiplying this up for the slurry produced from 100 dairy cows during the housing period it represents a potential fertiliser value of over £3,000.

To take full advantage of the nutrients in slurry it should only be applied:-

Slurry applied in the months February to April has a higher percentage of available nitrogen for plant growth.  So to achieve maximum benefit it is important to apply slurry to the grazing and silage ground during this period.

Soil analysis reports usually show that that there is no requirement for phosphorus or potash on grazing ground, especially, when the ground has received an early application of slurry.  In these cases straight nitrogen should be sown at a rate of 50 KG/ha (40 units/acre) after each grazing until late summer.  Depending on weather conditions and grass supply adjustments may need to be made on individual fields.  Where separated slurry is available there is the potential for this to be applied during the grazing season.  The separation process helps reduce the risk of cows rejecting the swards as there is less odour and sward contamination.  This practice has been used successfully on the CAFRE farms for a number of years.

For first cut silage harvested in mid May, 120KG/ha of Nitrogen is required.  This can be supplied from both slurry and inorganic fertiliser.  When applying inorganic fertiliser it is important to make an allowance for the nutrients supplied from slurry.  If too much nitrogen is applied the fermentation of the grass in the silo will be affected reducing livestock performance the following water.  To help ensure a satisfactory fermentation allow one day for every 2.5KG nitrogen (2 units/acre) applied between application and harvest date.  When ordering fertiliser for silage ground fertilisers with high levels of Potash and Sulphur should be used as these are the two nutrients that are generally under supplied.

With the increasing cost of inorganic fertiliser it is important to consider incorporating clover into both grazing and silage swards.  A good clover based sward can maintain a stock carrying capacity equivalent to grass swards receiving up to 200 KG nitrogen/ha/year.  Swards grazed by dairy herd replacements can offer the greatest potential for grass clover.  

It is important to make optimum use of slurry and manure and apply the correct amount and type of fertiliser in order to minimise pollution risk and reduce costs whilst achieving optimum grass growth.  CAFRE are organising a number of Nutrient Management training courses if you would like to be invited to one of these course you should contact you local CAFRE Dairying Development Adviser.  In addition interest based nutrient planning calculators are available via the rural portal at http://www.ruralni.gov.uk/index/environment/countryside_management_main/farm_waste_management/farm_nutrient_management_calculators.htm

Phosphate fertiliser should only be sown if soil analysis shows there is a requirement.

A good clover sward can be equivalent to a grass sward receiving up to 200KG nitrogen/ha/year.