NEW TECHNICAL FERTILISER GUIDE HIGHLIGHTS IMPORTANCE OF NITROGEN TO SULPHUR RATIOS

Focusing on the ratio of Nitrogen to Sulphur in growing grass can help producers increase yields but also improve sugar and protein contents, a new CF Fertilisers technical guide suggests.

 

The approach outlined in ‘The difference Sulphur could make to your grass’ can easily result in a return of £5 to £15 for every £1 spent on putting Sulphur into you fertiliser programme.

Dr. George Fisher of CF Fertilisers

 

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Sulphur is at least as important for grass growth and quality as Nitrogen, Phosphate and Potash.

 

If you don’t have enough Sulphur available to plants to produce the required proteins then yield drops but as proteins are involved in all plant processes, it also effects crude protein levels and sugar contents.

 

Grass requires almost half as much Sulphur as Nitrogen but although much of this used to be available as atmospheric deposition from industry, this is no longer the case.

 

The undeniable fact is the vast majority of grass production areas in Britain are now S-deficient.

 

Measuring Sulphur levels in the soil is at best unreliable and variable, so it is much better to test the growing grass itself, he explains.

 

The amount of S in grass is normally in the range 0.2 – 0.4% with at least 0.25% being needed to avoid the effects of deficiency.

 

Whilst knowing the actual amount of S in grassland is a good starting point, what is far more informative is understanding this relative to the amount of N there is in the sample, so you need to make sure that any test you undertake can provide this, too.

 

A ratio below 10:1 shows Sulphur is OK. Anything above 10:1 with an S content of less than 0.2% is deficient. It’s very easy to sample growing grass, so get an analysis done and make a decision.

 

Diagnosing Sulphur deficiency with Grass N:S ratios

 

N:S Ratio

Grass S less than 0.25%

Grass S more than 0.25%

Over 13.1

S-deficient

S-deficient

10:1 to 13:1

S-deficient

Grass OK

Below 10:1

Grass needs more N

Grass OK

 

 

Because sulphate can move through the soil profile, the general approach should be to apply Sulphur ‘little and often’ to maximise efficiency and optimise the effects, George Fisher adds.

 

This is why it is best to apply S with every Nitrogen fertiliser application and why NS, NKS and NPKS true granular compounds are so effective, providing a range of opportunities to optimise N and S ratios whilst addressing other potential nutrient needs.

 

The overall financial gains will depend on product prices, yield and quality impacts as well as how the benefit is captured and farmgate product prices.

 

Making more milk or meat captures more value than replacing concentrates, for example, but generally you can expect a £5 to £15 return for every £1 you spend on well managed Sulphur applications.