Make your grassland fertiliser work harder

By: Jez Wardman

Fertiliser has always been a good investment for livestock farmers, whether you’re growing grass for grazing or looking to reduce feed costs through better silage management. Applying the optimum level of nitrogen at the right time will guarantee a healthy yield and good quality grass.

Agronomy Advice - Make your grassland fertiliser work harder
Agronomy Advice - Make your grassland fertiliser work harder
Nitrogen still gives the best return on investment

Nitrogen drives grassland yield. It is the key to achieving high dry matter yields and is often strategically used to increase production as it is needed. It is this ability of nitrogen fertiliser to drive grassland yield that gives this return on investment.

Let's look at some figures:

First Cut Silage with an application of 120kg N/ha, you can reasonably expect to achieve 5.5 t DM/ha, with a nitrogen cost of €102 per ha (N at €0.85/kg). This will produce 20 tonne FW/ha of silage, valued at €25 tonne/FW giving you €500 per ha. That’s a return on investment of around 5 to 1!

Second Cut Silage cut with an application of 90kg N/ha, you can expect to produce 2.5 t DM/ha, with a nitrogen cost of €76 per ha (N at €0.85 /kg). This will produce 9 t FW/ha of silage. Valued at £25 tonne/FW  is €225 per ha. That’s a return on investment of around 3 to 1!

The message is clear - applying nitrogen fertiliser to grassland still gives one of the best returns on investment on the farm. 

Don't forget about sulphur

For grass to use the nitrogen efficiently it is important that no other nutrient is limiting, particularly sulphur. Recently we have been seeing significant responses to sulphur, particularly on intensive silage swards. Not surprising as atmospheric deposition has declined significantly since the 1980’s.

Sulphur applications have a positive effect on nitrogen use efficiency. Meaning that more of the applied nitrogen is converted into grass protein which has the double impact of improving dry matter yield and reducing nitrogen losses to the environment.

The only sure way to avoid sulphur limiting nitrogen response is to apply both nutrients at the same time. YaraBela nitrogen plus sulphur fertilisers all contain nitrate nitrogen together with all important sulphur.

Typically the yield response to sulphur will be about 10% although on lighter soils with low organic matter this can be nearer 20%.  Using the above figures and a cost of sulphur of €0.14 per kg S this gives a return on investment in sulphur of 3.5 to 1 for first cut and 2 to 1 for second cut. So there is a healthy return on sulphur even without taking into account quality improvements such as higher percent protein or an increase in metabolisable energy content.

Remember to correct soil pH

Another of the most common mistakes that prevents these impressive returns, is incorrect soil pH. On grassland, the target soil pH is 6.0. Achieving the correct soil pH allows the soil biology and earthworms to thrive and break down plant residues, animal manures and release nutrients required for healthy plant growth.

Correcting soil pH will also increase the availability of of all nutrients, ensuring you get a better return on your investment in nitrogen.