Getting more from your nitrogen investment
As the fertiliser market continues to fluctuate听because of听political unrest in the Middle East the hope听of prices dropping and staying down appears听increasingly听unlikely.听Cashflow, timing of use, storage and听having听the time to follow markets makes it听very difficult听to always be on the right side of price fluctuations.听If we听can't听control fertiliser prices, we need to ensure that every kilogram of nitrogen (N), phosphate (P) and potash (K) applied delivers the maximum return on investment.听听
Some of these factors come long before听getting a听price of fertiliser.听
- 听Are soil pH鈥檚 at a level to ensure听maximum听uptake of any nutrient听required?听
- Are soil phosphate and potash levels sufficient to get the full growth potential of any nitrogen applied?听
- What is the yield potential of the crop?听
- How much N, P&K do you need to grow that crop?听
- Has the N,听P and K in any organic manures听available听been factored in?听
- Are weather conditions suitable for fertiliser applications?听
Grass yields drop every year after establishment due to an ingress in weeds,听weed grasses and drops in soil fertility.听This means silage and grazing fields will have a differing yield potential based on the age of the sward.听
A ley in year听five听will have approximately 70% sown species compared to 98% in year听one.听A review of intermediate and late perennial ryegrass cultivar yields听from grass trials听shows that by year听six听the difference in yield is around 5t DM/ha听less than in year听one.听If the yield potential of fields differs according to the听age of the grass sward听one way to ensure maximum return on听nitrogen spend is to听tailor听the nitrogen rate according to yield potential.听听
Phosphate and Potash rates听remain听consistent as they are already听directly related听to听the yield of a crop.听If a typical听nitrogen听application for a grazing and听two听cut silage system is 220kgN/ha听we are feeding a crop to yield approximately 11.5t DM/ha.听If leys within their first听three听years have potential to yield 13-14t DM/ha听this application rate could be听limiting their听yield听potential.听Conversely if we are applying the same rate to fields听eight听years听plus,听which are yielding between 6-7t DM/ha then we are feeding them beyond their听yield听potential-wasting money.听
The average response to nitrogen applications is 20kg of dry matter for every 1kg of nitrogen applied. Based on our typical application rate of 220kg nitrogen if we apply an additional 30kg/ha of nitrogen over the year to swards one to three years old we could yield an additional 600kg DM/ha. This is the equivalent to an extra three bales/hectare for an additional cost of 拢40/ha*. Equally the fields with a yield potential of 9t DM/ha could be receiving 90kg/ha less N without a yield reduction. A saving of 拢119/ha*. 听
Varying application rates by field does create听additional听work but this could be听balanced听by grouping fields by age, such as leys听one to three听years old,听three to six听years old etc.听It听will听require听additional听planning to ensure the rate of P&K applied still matches that听required听for offtakes and maintenance.听听
In a climate where winters are predicted to be longer and wetter, there will be a greater requirement for forage听reserves.听Dry spells in summer become听could become听more common and fertiliser prices continue to be volatile targeted actions such as this can maximise forage output without adding cost.听
*34.5% ammonium nitrate (AN) at 拢455/t听
Top听tips:听
- Prepare a nutrient management plan听which accounts听for organic manures.听
- Review field performance and grass sward compositions听to听identify听fields with highest yield potential.听
- Target nitrogen to crops with the highest potential.听
Lorna Galloway, Senior Consultant,听Lorna.Galloway@sac.co.uk
Posted by SAC Consulting on 17/08/2026
