Fertiliser Advice for Cereals Factsheet

Teagasc recently published a compendium of 20 factsheets providing the latest technical advice on soils, nutrients and fertiliser. The twelfth of these is about Fertiliser advice for cereals and can be read here. All 20 will be published here on Teagasc Daily

Farmers are urged to focus on Nutrient management planning, optimisation of soil fertility, using organic manures strategically and increasing clover in swards, all balanced with prudent fertiliser usage.

Complete soil sampling for cereal crops and use the results to complete a full Nutrient Management Plan (NMP). The NMP should focus on:

• Lime is the cheapest fertiliser and makes all other nutrients more available
• P & K requirement should be matched to off-takes at soil Indices 1 to 3
• At soil Index 4 where pH is lower than 7, then there is no P & K required
• In fields where straw was chopped, or organic manures applied, you can reduce P & K requirements
• ‘Straight Fertilisers’ products may be suitable for some sites where either P or K are at Index 4
• At soil Index 1 or 2 drill the compound fertiliser at sowing time

Nitrogen

The ratio between the value of grain and the cost of N has doubled in the last 12 months, so the economic yield response to the application of N has changed

• All crops have a N response curve, which reaches a point where the yield response to N flattens out. This point is called the agronomic optimum N rate (see curve below - red line)
• The graph will also reach a point called the economic optimum rate where the additional yield will not cover the cost of the N applied. This is the Break Even Ratio (BER) (blue line). This BER point on the curve will occur this year before you reach the agronomic optimum nitrogen rate (see table 1)
• Based on the current cost of N versus the current value of grain, research shows that the maximum N rate at which this BER occurs is 20 to 30 kg/ha lower than the current Teagasc Green Book recommended N rates (See table below)
• Reducing the nitrogen rates may reduce yield by 0.2 to 0.5 t/ha, however despite this yield drop, and factoring in the costs of nitrogen, these crops will give a better return than continuing as normal

N rate kg/ha

Example 1: Winter wheat 10 t/ha yield; N index 1

Note: Allowance of 20 kg N/ha per tonne grain yield/ha above reference yield (see Nitrates Directive)

210 kg + 20 kg (Bonus Yield) = 230 kg/ha – 30 kg/ha = 200 kg N/ha (Economic Opt. N Rate)

Example 2: Spring feed barley 7.5 t/ha yield; N index 1

135 kg + 20 kg (Bonus Yield) = 155 kg/ha – 30 kg/ha = 125 kg N/ha (Economic Opt. N Rate)

Deirdre Hennessy, Seamus Kearney, Mark Plunkett, David Wall, Mark Moore (Editor), Pat Murphy, Stan Lalor, were the main contributors to this series of leaflets. Numerous colleagues from Teagasc AGRIP, CELUP, REDP, Signpost, PR dept. and advisory service also participated.

To access the entire compendium of 20 factsheets see Soils, Nutrients and Fertiliser Factsheets   Find more information on this topic in Soil & Soil Fertility