10 steps to a better return from fertilisers – even at today’s prices

Even at today’s prices artificial fertilisers can provide a significant return on investment, provided their use is targeted.

Tight supplies, due to global demand outstripping supply, mean farmers need to make the most of fertiliser and also maximise the nutrient value of muck and slurry.

If farmers target nitrogen applications carefully, even at prices of about £265/t (34.5% N), most can expect an estimated return of £3 for every £1 spent on nitrogen fertiliser. But following these 10 simple tips could provide even better returns on investment than experienced on many units:

1 Ensure optimum nitrogen rates are applied. Follow “The Grassland Rule” to calculate cutting date

Nitrogen is the most important nutrient, with a complex behaviour in soils and calculating correct application rate can be difficult.

As a rule of thumb, “The Grassland Rule” of 2.5kg/ha a day of expected grass growth (2 units/ha a day) can be used to calculate nitrogen requirements to optimise yield and quality.

2 Take account of the grass yield potential

Fields can be separated into grass growth classes, with soil-available water, soil type and rainfall influencing the site classes, which range from very poor to very good. Each of the sites has a yield potential associated with it and using this data nitrogen rates for the season can be adjusted.

On the “Good” and “Very Good” sites an extra 40 to 80 kg/ha of nitrogen may be justified for the site to fulfil its potential. Site class information will also identify stocking rate potential. “Very Good” sites can carry a higher stocking rate for longer in the season.

3 Fully account for nutrients supplied from organic manures

Manures and slurry have a value as providers of nutrient.

For example, an application of slurry at 40t/ha would provide N worth £17/ha, P2O5 worth £26/ha and K2O worth £46/ha, a total contribution of £89/ha.

4 Use the most suitable form of nitrogen

Nitrogen source is important, with the two principal choices being between ammonium nitrate and urea.

Trials conducted over the past 35 years have shown ammonium nitrate to be more effective, with crops of first-cut silage yielding about 7% more where ammonium nitrate was used compared with urea.

A recent DEFRA project showed that up to 58% of the total N applied in the form of urea was lost through ammonium volatilisation, compared with a maximum of 13% from using ammonium nitrate.

5 Ensure you use a quality product

Fertiliser quality can have an impact on spreading performance.

A range of products was tested and a comparison of the spreading performance made when applied with a spinning disc (12m) and pneumatic machine.

The non-size-matched products demonstrated clear visual evidence of particle segregation between the centre and outer parts of the spread pattern that would result in an uneven distribution of nutrients.

One noticeable issue was the performance when using the pneumatic spreader. Although it was successful in reducing the co-efficient of variation when applying urea, it could still not achieve an acceptable spread pattern.

6 Ensure the correct timing of nitrogen

Timing of nitrogen at the start of the season is also important.

Apply it in line with grass requirements and expected turnout. Too-early applications can produce grass that is not used where ground conditions are unsuitable for carrying stock. Applications made too late will leave free nitrogen that is not incorporated into the protein content of grass dry matter.

7 Apply sulphur to increase grass DM yield and quality

With sulphur deficiencies increasing in the UK, larger and more frequent responses are seen to applications of sulphur in both first and second-cut silage.

Trials in 2003 showed an average yield increase from applying sulphur of 11%.

Other than increasing yield, the benefits of applying sulphur include improved nitrogen use, which will help produce better quality silage with higher, ME values.

8 Ensure P&K is applied to areas that are low to maximise the effects of nitrogen

Phosphorus is an essential nutrient for crop growth and development. It plays a big role in energy in the plant, which is required for the uptake of other nutrients.

Recent price increases may encourage some farmers not to apply phosphate, particularly where soil indices are high. But applications of fresh phosphate have been shown to improve response to nitrogen, particularly when applied together in spring.

Potassium is vital for regulating water supply and cell turgidity and an adequate supply is essential for maximising yield from applied nitrogen.

Where grass is cut for silage or hay, removal of potassium in the crop can be large and the rate of following applications must be matched to future grass management.

9 Ensure soils are at the correct pH

Grass growth is optimised at pH6. Always check soil pH and correct with a suitable liming product.

Grass growth will be compromised by acid patches and give poor nitrogen use efficiency, decreasing the return on the applied fertiliser.

Inappropriate pH levels also reduce availability of other soil nutrients such as phosphate.

10 Ensure spreaders are accurately calibrated

Increases in the coefficient of variation (CV), the measure of uniformity of distribution, above an acceptable value for field conditions of about 10%, can have a serious financial impact.

In arable crops, visible indications of inaccurate spreading are unlikely to be detected until the CV is more than 20%, but in grass it can be difficult to identify whatever the CV. Therefore it may go unnoticed and uncorrected on many grassland farms unless regular testing is carried out.

Evidence from trials has estimated crop quality losses in grass silage from poor spreading as the ME fell from 11.3MJ/kg DM from acceptable spreading to 10.7MJ/kg DM where the CV reached 30%.

This fall in ME could be translated into a loss of milk of 44 litres a cow over a typical 200-day cycle. Assuming a price of 25p/litre for milk, this equates to a loss of £11 a cow.

A spreader requires annual calibration for all products applied to minimise the effects of inefficient fertiliser use. But testing is often under-used.

Rising feed costs mean making the most of grassland through careful fertiliser use can provide a significant saving.

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