How to manage your aftercut fertiliser to maximise silage yields and quality
Managing aftercut fertiliser applications will be essential in maximising grass yields and maintaining quality this season following the exceptionally wet start to 2021.
Soil nitrogen (N) reserves are likely to be low, but other important nutrients such as phosphorus (P), potash (K) and sulphur (S) also
need to be factored into application decisions as grassland could easily run out of steam as the season progresses.
Overall grass production and key quality factors such as crude protein are likely to suffer this year if dairy and livestock producers try to rely solely on organic sources.
Even if you can apply 30m3/ha (2,700gals/acre) of 4% DM slurry, you will be well short of the RB209 recommendations for N, P K and S.
In terms of nitrogen alone, such an application will only provide 17 of the 90kg N/ha recommended for a high yielding system.
Inorganic fertilisers will, therefore be needed, and their use shoud be balanced against manure application. A good quality, multi-nutrient NPKS, true granular compound will be the ideal choice for many.
As well as focusing on nitrogen, the importance of other nutrients such as potash, for example, cannot be overlooked, especially in
situations where plants are under stress.
Potash is essential in ensuring N is taken up by the roots effectively and has an important role in the plant’s ability to withstand drought.
Its role is important in less than perfect years and can often be overlooked if you’re just focusing on the relationship between N levels
and yields.
In trials over three years, where 320kg potash/ha was applied to soils with a K index of one, the average ME increased from 10.9 to 11.5
MJ ME/kg DM. This is considerable in terms of utilising home-grown forage energy to support profitability.
Product choice is key
CF MultiCut Sulphur (23-4-13 + 7SO3) is a good starting point for addressing many grassland nutrient needs. It is an all-season, high
nitrogen/high potash product, ideal for multiple cuts of grass silage, with reduced phosphate content to help maintain soil P and K status.
It’s the ideal product for balancing nutrient offtakes to maintain soil fertility, and performs well on its own or alongside spring
slurry applications.
Application rates up to 450kg/ha for first cut, 350kg/ha for second cut and 280kg/ha for third cut are appropriate, but these can easily be reduced if organic manures are being used.
As well as helping keep P and K in balance, the sulphur contained in MultiCut Sulphur has a valuable role to play in terms of maximising yields and boosting crude protein levels.
UK producers are using a lot less N on grassland than they did 30 years ago as a result of NVZs and better farm practices. This is likely
having an impact on grass quality as nitrogen is a key element in protein production.
Sulphur has a profound effect on the ability of grassland to utilise N and hence inadequate levels can really drive Nitrogen fertiliser Use
Efficiency (NfUE) down.
| CF MultiCut Sulphur (23-4-13+7S03) application rates | |||||
| Product application rate (kg/ha) |
Potential application |
N kg/ ha |
P205 kg/ha |
K20 kg/ha |
S03 kg/ha |
| 450 | First cut | 104 | 18 | 59 | 32 |
| 350 | Second cut | 81 | 14 | 46 | 25 |
| 280 | Third cut | 65 | 11 | 37 | 20 |
Critical role of sulphur
It’s not that long ago the UK got 70 to 80kg/ha of sulphate simply falling out of the sky every year, but as the industry has cleaned up its
act, this has fallen to below 10kg/ha and in many areas, below 5kg/ha.
It’s not unrealistic, therefore, that atmospheric sulphur levels being only 5% of what they were is having just as much of an effect on
crude protein levels as applied nitrogen levels being reduced by 50%.
Trial work carried out by CF Fertilisers, showed that restoring sulphur levels in grassland lifted proteins by 7% and increased yields by up to 2.0t/ha.
More than ever this year, it’s important to use a full nutrient management plan, where the N, P, K and S applied as fertiliser to every field is informed by soil analysis and balanced against organic manure nutrients.
Making up a forage shortfall with bought-in feeds can cost twice as much as producing what you need by getting your grassland
management and fertiliser use right in the first place.
So, plan your fertiliser needs carefully, think beyond just nitrogen and invest wisely and you should still be able to maximise your
production of high-value, home-grown forage, despite the challenging start to the year.
