Optimise Forage Quality with Effective Sulphur Fertilisation

Sulphur fertilisation is necessary for optimal grass production. Despite great attention to sulphur, sulphur levels in forage are still regularly too low. Too low sulphur inputs result in a decrease in dry matter yield and low protein content in grass. The use of sulphur in grassland requires a good strategy in the fertilisation plan.

Grass has a high sulphur requirement that varies between 30 and 45 kg/ha per year. Sulphur (S) is taken up by grass in the form of sulphate (SO42-). Converting sulphur requirement to sulphate requirement means that grass absorbs 90 to 135 kg sulphate per hectare per year.

Is all sulphur available?

Sulphur is available from soil and organic manure. With an average feed of cattle manure, 15 to 25 kg of sulphur is given. Sulphur is also available from soil organic matter. However, sulphur from livestock manure and from soil is only available to grass after mineralisation.

Mineralisation requires sufficient moisture and a higher soil temperature. In particular, soil temperature still lags in early spring. Then only 5 to 8 kg of sulphur is available from the slurry and an additional sulphur fertilisation of about 40 kg of sulphur is needed. The first and second cuts of grass in particular are at risk of deficiency because of the low soil temperature and therefore low mineralisation in spring.

Sulphur supply

Whether sulphur should be fertilised in the third and subsequent cuts depends on soil properties such as the sulphur delivering capacity of the soil. This is the amount of sulphur that can still be released during the growing season. The sulphur delivering capacity is listed on the soil analysis and gives an estimate of how the sulphur supply is during the growing season. Cattle farmers on peaty soil should be careful with sulphur application because peaty soil still delivers a lot of sulphur later in the season. The advice is to tailor sulphur fertilisation later in the season. Because too much sulphur hinders the uptake of copper and selenium. This, in turn, can be detrimental to cow health.

Clover needs sulphur

The popularity of grass clover is increasing among livestock farmers. Clover can make an important contribution to nitrogen supply, but it also needs sulphur for good production. This is because a sulphur deficiency has a detrimental effect on the development of the root nodules. This is because in the root nodules, nitrogen is bound from the air after which it becomes available for plant growth.

According to the fertiliser recommendation, grass clover only requires nitrogen fertilisation for the first cut. The donation depends on the nitrogen delivery capacity of the soil. A nitrogen fertiliser with sulphur then has extra added value to maintain crop production levels for both grass and clover.

Sulphur and protein quality

Ultimately, the goal is a high dry matter yield and high protein content in the grass. Sulphur is an important building block of amino acids and protein. It is essential for building the high-quality protein, the Intestinal Digestible Protein (IDP), in grass. There is a direct link between IDP, milk and milk protein production. Deficiency of DVE in the ration directly inhibits milk production. IDP is strongly related to plant characteristics, fertilisation and ensiling method. In addition, a favourable ratio between IDP and UPB (Unsettled Protein Balance) is important. If sufficient sulphur is fertilised and an optimal mowing and ensiling moment is applied, more IDP and less UPB will enter the silage. In this way, sulphur has an important role in forage yield and grass quality. An important key figure for this is the nitrogen-to-sulphur ratio. The target value of grass silage is 12. If this value is higher, there is a sulphur deficiency.

Sulphur and animal health

Milk production is obviously an important indicator of whether there is enough sulphur in the forage, but sulphur is also necessary for overall animal health. A sulphur deficiency not only lowers milk production, but causes a dull coat and bad claws in the cow. This is because the hair and claws contain keratin of which cysteine, the sulphur-containing amino acid, is an important building block. A good sulphur supply for dairy cattle therefore requires 1.5 grams of sulphur (S) per kg of dry matter in the grass. Tailored fertilisation with sulphur can prevent deficiency and is therefore good for milk production and cattle.

Synergy between sulphur and nitrogen

The latest addition in the field of nitrogen-sulphur fertilisers is Dynamon from OCI. This fertiliser has an ideal N/S ratio of 24% N and 7% S.

Unique is the synergy between nitrogen and sulphur. If both elements are available in sufficient quantities, a plant can absorb and utilise N and S effectively and easily. More importantly, to make proteins, the plant needs both nitrogen and sulphur. If one of the elements is missing, synthesis is affected with consequences for yield and quality.

Dynamon is applicable and effective in all forage crops.

Want to know more about OCI Dynamon? Read the information at www.oci-dynamon.co.uk.