Sulphur Index

S-Index helps you optimise Sulphur use on grass.

How to use S-Index?

S-Index takes 5 nutritional parameters from your silage analysis and combines them with your mineral analysis to produce a single value that you can use to show whether the Sulphur supply to the grass was optimal, insufficient or excessive. It’s a handy tool to compare to other silages and measure improvement over time.

• S-Index < 85: Too little available S was present for the grass. This means you are losing between 10% and 20% dry matter yield. If you have fertilised no S or too little S, you can provide more sulphur through artificial fertiliser applications, thus achieving a higher yield and a better protein quality.
• S-Index between 85-92: The grass has grown with a narrow S-provision. If you have fertilised no S or too little S, you can provide more sulphur through the artificial fertiliser applications. You will then achieve both a higher yield and a better protein quality.
• S-Index between 92-108: This is the target value. The sulphur provision for the grass was optimal. You do not need to make any changes to S applications for next season. 
• S-Index between 108-115: The sulphur provision for the grass is on the liberal side. A Sulphur Index greater than 115 shows excessive much sulphur was available during the growth of the grass. The S content in the crop is extremely high and you should take this into account when formulating rations. The utilisation of copper (Cu) and selenium (Se) can be at risk. If you have fertilised a lot of S, then in future you should use a lower dose.