Advice on silage aftercut nutrition in a late spring

Livestock farmers should invest in good aftermath nutrition after the first cut to ensure they maximise yields and quality from second-cut silage.

Cheshire-based independent grassland adviser George Fisher, of George Fisher Consulting says this is especially important in years where there is a late spring affecting grass growth.

 

See also: First-cut silage runs high risk of slurry contamination

First-cut tips

  • Don’t delay cutting: make up bulk with more cuts
  • Apply after-cut fertiliser as soon as possible after cutting
  • Use a granular compound rather than a blend for better uptake and more landing sites. Granular compounds have all nutrients contained in each granule.
  • Don’t skimp on potash if you want high-energy silage
  • Use sulphur to boost protein, yield and nitrogen use

Delaying cutting date and subsequent post-cut fertiliser applications after a cold spring will limit silage quality and yield.

At this time of year, Dr Fisher adds, the maturing of grass loses 0.5-1 D value/day, so a 72 D value today could be 71 tomorrow or the day after.

“It will be far better to take a first-cut close to the same time as usual and then invest in a full aftercut nutrition programme to ensure second-cut delivers the right yields with optimum protein and sugar content,” he says.

“Ensuring you manage grass properly now is essential to ensure adequate forage supplies for the coming winter.”

Aftercut nutrition advice

While farmers might be tempted to save money by relying on manure and slurry for grassland nutrition, James Holloway of CF Fertilisers warns that this approach could leave farms “woefully short” of feed.

Dr Fisher adds that growers supplementing organic manures with straight nitrogen may find they are short of potash and sulphur. 

He says that on farms that have applied as much slurry as possible earlier in the year, available nitrogen will have been lost by now.

What to apply

Dr Fisher recommends soil testing so farms know what fertiliser is required, before following with a slurry application. He says an N:K:S fertiliser should set up second cuts well.

Even a 30m3/ha (2,600 gallon/acre) application of a 4% DM slurry will be well short of RB209 recommendations for nitrogen, providing only 19kg/ha of the 100kg/ha recommended for a 5t DM/ha grass crop.

Nitrogen (N), potash (source of phosphate) and sulphur (S) will therefore be required, explains Dr Fisher. “Work from your soil analysis and take into account all the nutrients from manures.”

Typical second-cut applications for optimum growth are:

  • 80-100kg of N/ha
  • 25-40kg of S/ha
  • 60-90kg of potash/ha

What nutrients does slurry provide?

Nutrient

Typical requirements (kg/ha)

Nutrition of slurry 30cu m/ha (2,600gal/acre)

% provided by slurry

Nitrogen

100

19

19%

Phosphate

34

14

41.17%

Potash

120

57

47.5%

Sulphur

40

2

5%

*Requirements for second cut on a soil p and K index of 2

When to apply

After-cut nutrition programmes are best applied as soon as possible. Once first-cut is harvested, freshweight production drops about by 370kg/ha for every day’s delay in nitrogen application, Mr Holloway explains.

“Research has shown delaying aftercut fertiliser for a two-week period will lead to a potential 20-25% yield loss, which can be 1t/ha DM,” he says.

He adds farmers should be prepared to spread slurry more thinly rather than be caught out by having to leave cutting until six weeks after the last application.  

“If you focus on getting high quality from your first cut you can then use subsequent cuts to build silage stocks,” he explains. “Focus on quality. If you need more bulk, take more cuts.”

Why to supplement with phosphate (P), potash (K) and sulphur (S)

Phosphate

  • P is vital for energy capture by plants through photosynthesis.
  • Test soil and strive to maintain a soil P index of 2.

Potash

  • A three-year trial adding 320kg/ha potash to soil with a K index of 1 lifted average silage ME from 10.9 to 11.5MJ ME/kg DM.

Sulphur

  • Trials are showing the benefits of sulphur applications in maximising crude protein and facilitating better nitrogen use.
  • Sulphur plays a vital role in amino acid production (methionine and cystine).
  • One trial restored optimum sulphur levels to lift protein by 7% and yields by nearly 2t/ha.
  • A sulphur containing granular compounds such as 25-0-13-7SO3 or 25-0-6-6SO3 should be considered, particularly this year.

Compaction caution

With high water tables, independent grassland adviser George Fisher, of George Fisher Consulting acknowledges many producers will have to consider compaction this silage season.

  • If possible keep off wet fields especially 48 hours after heavy rainfall
  • Reduce machine size and total axle loads, as loads greater than 3.5t can cause serious and permanent compaction
  • The greater the weight of the vehicle and the greater the tyre pressure, the deeper the potential compaction
  • Reduce the pressure on the ground with larger tyres and lower inflation pressures to spread the weight over a larger area
  • Consider established wheelings or reduced traffic systems
  • Avoid overusing entrances; use a separate exit if possible