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Soil Fertility is the Key for Increased Profits

19 February 2019
Type Media Article

By Marion Fox, B&T Drystock Adviser, Teagasc Galway/Clare

It is the time of year to take soil samples if you have not previously done so. It is critical piece of information that is needed to see what the status of your soil is. Samples should be taken up to a max of 4 ha and are relatively cheap as there is valuable information that can be found as a result. To improve soil fertility there are a number of key steps to follow: firstly by correcting the PH of the soil i.e. lime followed by the Phosphorus and Potassium. If there is good quality grass fed, costs can be reduced therefore, more money in your back pocket. 

Soil Sampling Procedure:

Sample fields in a W pattern with up to 20 cores up to 4 ha. Soil sampling should take place every 4 years. The farm should be divided up into fields depending on if they are silage fields or grazing fields. Soil samples should not be taken 3 to 6 months after the application of P and K fertilisers. Where lime has been applied allow for a time of 2 years before sampling for the lime requirement.


Ground limestone is one of the most popular and cheapest forms of lime that can be applied. The application of lime has an influence on the availability of stored nutrients in the soil. The optimum PH of soil for grassland is PH 6.3. The target is to have the soil at the optimum PH in order to optimise soil fertility. If the lime requirement is greater 7.5t/ha or 3 t/ac, it should be split into 2 dressings in year 1 and year 2. Some farmers may choose to apply granulated lime as compared to ground lime, it is more expensive, but has a quicker response and should be treated as a fertiliser; it also needs to be applied each year. If the soil is not at the correct PH you will waste money on fertilisers. Lime costs approximately €22- €25 per tonne spread depending on what part of the country you live in.

Phosphorus and Potassium:

Building the P and K levels in the soil can take a number of years to happen and does not occur over night. The target is to have both at index 3.  It is very important that you adhere to the soil test result in order to access the amount of P and K that is required. It is advised to apply recommended P and K rates annually and build the soil P and K over time. Apply 50% phosphorus (P) in the spring and the remainder during the growing season in 2-3 applications. Potassium (K) should be applied during the growing season and apply in August/September to build up if soil indexes are low.


Nitrogen is the main driver of plant growth. Nitrogen should be applied when soil temperatures reach 5-6 °C (when the grass begins to grow). Check weather and apply when conditions are suitable, a little rain will help Urea move into the soil. The aim is to apply 23 units/ac in the 1st split in February and have 60 units/ac applied by April on higher stocking rate farms. Urea 46% N (€0.80/kgN) is a cheaper source of N compared to CAN 27%N (€1.11/kgN).

Organic Manures:

Slurry and farmyard manures are a very valuable source of fertiliser on farms. If applied in the spring it will increase Nitrogen recovery by 3 units/1,000 gallons. Slurry should be applied to fields that are low in P and K as it is a good source of these nutrients. The aim should be to have the majority of the slurry applied before April (70%) and the remainder by mid-June. Low emission slurry spreading should be the preferred option i.e. band spreading or trailing shoe.

Soil samples cost €25 per sample so I would recommend to contact your Teagasc Advisor or Private Agricultural Consultant to get samples taken.