Slurry tanks on many farms remain full following the prolonged wet spell. Spreading should begin as grass cover is removed from fields either through grazing or a silage cut.
Farmers in zones 1 and 2 of Northern Ireland have nearly all received their Soil Nutrient Health Scheme (SNHS) soil sampling results. Fields that have been identified as low in P or K should be the ones where slurry is targeted if possible. Silage fields should also receive preference for slurry spreading.
Watery slurry will be more suited to LESSE application and tanks should be diluted where possible. Thin slurry will help to avoid fibre trails that can sometimes be left behind following a LESSE application.
SNHS will also have identified fields that are low for pH and a plan should be in place to correct these as soon as possible. Target fields with the highest lime requirement first, as these may need more than one application to raise pH levels. The ideal time for applying lime is late summer/autumn as the ground is firm and silage cuts have been taken from fields. At a pH below 5.5, only 77% of the bag nitrogen applied is utilised. Correcting pH will give a good return on investment due to the enhanced fertiliser response rate that will be gained.
Late fertiliser application this year will mean that most fields are behind where they usually are in terms of the total nitrogen applied to date. The best return for fertiliser spread during the year will be in the period May to July with 25-30kg DM of grass grown for every kilogram of additional nitrogen sown. A 50kg bag of fertiliser could thus produce an additional 1.1t of silage freshweight if growing conditions are favourable. Plan now to catch up on annual fertilizer application rate targets. This should be done on a ‘little and often’ basis rather than applying a large amount all at once.
Maize drilling will have been delayed this year due to the wet spring. Optimum drill timing depends on soil conditions, temperature and seedbed moisture. Maize should not be drilled before soils have reached a consistent temperature for 3-4 days of 10 - 12°C. It may be possible to sow earlier maturing varieties, reduce the see rate by 5% and cut back on nitrogen marginally in order to make up for the late sowing and avoid a delayed harvest as a result. Late sown maize crops may catch up on crops sown early into cold wet seed beds.
On many farms, silage fields will have incurred machinery damage due to the wet autumn of 2023 and spring of 2024. Soil contamination in silage should be avoided where possible through:
- Setting the mower cutting height slightly higher than normal
- Ensuring that the tedder and rake are set correctly and are not disturbing the soil surface during harvesting operations.
- Avoiding cutting deeply rutted areas at 1st cut
Mycotoxin issues in dairy cow diets have been experienced on many units over the past 2 winters. Reducing soil contamination is one way of trying to reduce the mycotoxin load in silage.
When 1st cut has been taken from silage fields, you should assess damaged areas and repair them prior to second cut. This will involve levelling ruts, oversowing damaged areas, repairing drainage channels where necessary and earmarking some areas for aeration or a full reseed later in the summer. Some Scottish trials have shown that the first cut of grass silage, after exposure to compaction the previous autumn, showed the greatest reduction in yield. Up to 37% less silage at first cut was harvested from fields where there was tractor compaction in the autumn of the previous year.
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