Ahead of World Soil Day 2024, Germinal experts Dr Mary McEvoy, William Fleming and Harley Brown-Keech hosted a webinar on improving soil fertility to produce high-quality grass and forage that fuels livestock performance.
Below, you can watch the webinar and read through the detailed Q&A compiled by the panel for our viewers.
Watch:
Soil fertility Q&A:
When should sulphur be applied for the best results?
If applying on its own, the soil needs to be above 6–8°C for mineralisation to take place.
The ideal timing is generally from late April onwards. Sulphur is often applied alongside nitrogen, as both are essential building blocks for protein.
For grazing swards, aim to apply 20 kg S/ha per year using a “little and often” approach.
Can 220 kg/ha of nitrogen be produced from clover alone in a UK climate? Do we have the soil temperatures and average daylight length to achieve this?
Under ideal conditions and with good clover content, it is possible to achieve this level.
However, the NUE-Leg project is working to enhance this potential by matching the legumes with specific elite Rhizobia and providing tailored nutrition to capture even more atmospheric nitrogen.
That said, a more realistic figure at the farm level would be for clover to fix 100 to 150 kg N/ha. .
What percentage of new seeds typically establish successfully when overseeding?
The success rate of overseeding depends on numerous factors, including the level of thatch, soil conditions, weather and the type of seed sown (e.g., tetraploids, diploids, clover or herbs). Because of these variables, it’s challenging to quantify success as a percentage.
The best way to assess success is by measuring the additional dry matter (kg DM/ha) produced, the extra silage harvested or improvements in livestock performance.
What is your advice for fields where late-sown crops after maize have failed due to cold, wet weather?
Where late-sown crops either fail or have poor establishment, there is little option but wait until the spring, when temperatures and weather improve. Generally it will be mid to late March before sowing conditions are favourable.
Looking ahead, there is growing interest in sowing cover crops into maize at the 6-leaf stage. At this stage, soil temperatures are warm, and the cover crop does not compete with maize for nutrients. This approach provides additional carrying capacity at harvest and offers grazing opportunities after the maize is harvested.
Why are the Irish and UK pH, P and K optimum targets different?
In recent years, Ireland has raised its target pH for grass-clover swards from 6.3 (for grasslands) to 6.5 to 7.0 to support clover growth. At this higher pH, clover and rhizobia bacteria function more efficiently, improving nitrogen fixation.
For phosphorous (P) and potassium (K), the differences arise from the testing methods used. Irish laboratories use the Morgan’s test, while UK laboratories use the Olsen’s test.
Additionally, the index scales differ: Ireland uses a scale of 1 to 4, whereas the UK uses a scale of 0 to 5.
How much carbon can be collected in one hectare of productive grassland?
Grassland has the potential to sequester between 1.5 and 4 tonnes of CO₂ per ha each year.