Fertiliser Use Efficiency

• With high fertiliser costs there is a temptation to cut back on nitrogen use. However if you use less fertiliser, you will grow less grass, unless you can improve nutrient use efficiency through better soil and slurry management and increased clover content of swards.
• The efficient use of fertiliser to grow grass is still more cost effective than buying in feed.
• At the height of the growing season, a top quality ryegrass sward will give a response of 30kgDM for every kg N applied.
• 70% of Greenhouse Gas emissions from agriculture are associated with Nitrogen fertiliser (its manufacture and use).

• Target early (Feb/Mar) applications of Nitrogen to young leys, drier fields and south facing slopes.
• If compaction is a problem, consider using a soil aerator to improve soil conditions in the rooting zone. This will improve N uptake and reduce losses as nitrous oxide gas.
• Invest in a soil thermometer to check conditions as grass will only grow if soils are above 50 degrees Fahrenheit.
• Keep application rates low (~20units N per acre) in Feb for each grazing and increase as growing conditions improve.
• Check phosphate indexes are at index 2 or above as available phosphate is crucial for early season growth. There is no economic response in applying phosphate to soils of index 3 and above.
• Urea (46% N) is a cheap source of N, but losses as ammonia can be high on warm sunny days, so apply in damp conditions and low rates.
• Don’t forget to take account of Nitrogen from slurry. Sample what you are spreading to get an accurate picture of how much slurry N is applied.
• Consider the use of an injector or trailing shoe to keep the grass clean and allow the cows to graze right down on the first rotation.
• Look after clover plants in the spring. Make sure the grass doesn’t shade out clover plants. Keep N rates low and avoid high covers.
• For more information on sulphur inputs on silage swards to increase efficient nutrient use, click here to read the Catchment Sensitive Farming bulletin.

In order to accurately spread fertiliser to the correct application rate, it is important to calibrate your fertiliser spreader on a regular basis. With input prices rising all the time, making sure that you are spreading what you think you are and that the machine is working optimally will help for efficient operation in the field.

A recent survey looking into resource management practices on farms across the south west has revealed that 32% of farmers always calibrate their fertiliser spreader.

The graph to the left shows the breakdown of farms by type that calibrate their spreader. 50% of arable farmers surveyed always calibrated their fertiliser spreader, compared to 25% of cattle and sheep farmers who never calibrated their spreaders.

Interested in looking at the different methods/costs in establishing white clover in an existing grass sward? Click here to read the Nutrient Wise Demos Factsheet.

Considering your options for grassland reseeding? Click here to read the Nutrient Wise Demos Factsheet.