Our Organisation Search
Quick Links
Toggle: Topics

Assessing soil fertility to reduce Impacts of increasing fertiliser Costs

Assessing soil fertility to reduce Impacts of increasing fertiliser Costs

In the last number of week’s fertiliser price predictions for 2022 are reaching unprecedented highs due to skyrocketing fuel and gas prices. Gas is a key ingredient in the production of all nitrogen sources. Tillage Specialist Mark Plunkett gives some advice on reducing fertiliser costs.

Impact of high gas prices

Gas is a key ingredient in the production of all nitrogen sources. Currently there are reports of fertiliser production plants ceasing production due reduced gas supply and price increases. At present this is doubling quoted prices for CAN compared to 12 months ago.  At this stage the fertiliser suppliers are not sure where prices will be in early 2022 when most fertiliser is purchased.

Now is a good time examine the possible impacts of high fertiliser prices and forward grain prices on crop margins in 2022?  Tillage crops utilise applied nitrogen (N) very efficiently and have a medium to high demand for both phosphorus (P) and potassium (K).  Efficient use all nutrients will be key and starts with taking fresh soil samples to establish soil pH, P & K levels.  Where soil samples have not been taken in the last 3 to 4 years plan to take soil samples over the coming weeks. 


Apply lime where required based on soil results to maintain soil pH 6.5 to 6.8 depending on crop rotation.  This will ensure the availability of major soil nutrients such as N, P, K, Mg and S plus it will increase crop uptake and efficient use of both chemical and organic fertilisers. 

Soil analysis

Reliable soil analysis will be invaluable information when making decisions on crop P and K requirements and tailoring rates.  In 2020 Teagasc’s soils database shows that ~25% and 38% of tillage soils tested at P & K index 4 (high fertility) respectively, giving the potential for cost savings. At soil index 3 maintenance rates of P & K are required to replace nutrients removed at harvest time.  While soils at Index 1 or 2 require additional P and K to build soil fertility levels.  Building soil fertility in 2022 may have to be evaluated and alternative nutrient sources such as organic manures should be considered to control higher nutrient costs on these low fertility sites.  Research evaluating P fertiliser application methods for spring barley clearly shows the importance of delivering P fertiliser close to the germinating seed on low fertility soils (Index 1 & 2).

Organic manures

Where supplies are accessible are a cost effective source of N, P & K.  To maximise the recovery of N from high N manures (pig & poultry) it is important to apply and incorporate within 3 to 6 hrs. Test manures in advance of application to know there nutrient values and adjust application rates to supply ~ 50% of the crops P & K requirements.  For example an application of 25mᶾ/ha of pig slurry (2,200gals/ac) can supply 52kg N, 20kg P & 50kg K/ha which is ~30% of N and ~50% of P & K requirements for a crop of spring barley.  Now is a good time to look at local sources of organic fertilisers and plan for spring crop utilisation.   


Straw incorporation will help reduce crop P and K requirements.  Straw contains approx. 10% and 50% of total crop P and K, respectively. For example the straw from a 10t/ha grain crop of winter wheat will return ~4kg P & 50kg K/ha.  This offers significant savings of ~€55/ha in fields where straw was chopped.

N fixing crops

Where N fixing crops such as beans or peas are grown in a rotation the following crops N requirements are reduced as they fix atmospheric N thus increasing soil N supply. Cereals grown after legume crops have up 30kg N/ha lower N requirement reducing N costs by ~€50/ha.

Urea v CAN

Further savings can be made by selecting Urea (46% N) over CAN (27% N) as urea tends to be 10 to 15% cheaper than CAN. Urea can be more difficult to spread but with good particle size distribution, a good spreader and accurate setting of the spreader, good spreading can be achieved across a range of bout widths. Urea can also be subject to ammonia loss which is increased by increasing temperature and under drying conditions.

Fertiliser Spreader Calibration Tool

Access the Teagasc Fertiliser Spreader Calibration Tool here 

Find out more information and advice from the Teagasc Crops team here. 
The Teagasc Crops Specialists issue an article on a topic of interest to tillage farmers every Thursday on Teagasc Daily