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“Sulphur (S) is vital for farming, but often in short supply in our soils, which can limit pasture growth and response to nitrogen (N),” says Ballance Science Extension Leader Katie Aitkenhead.

“Shortages of S usually occur in spring, when plants most need it. This is due to leaching losses of plant available S over the wet winter.” 

Sulphur is essential for both chlorophyll production (which underpins photosynthesis) and protein formation. It’s particularly important for clover, as the Rhizobia bacteria in the root nodules need it for N fixation. 

If the soil is lacking in S, clover becomes less vigorous and abundant. In pasture, young, newly emerging leaves will be pale green or yellowing. 

If you suspect an S deficiency, soil and tissue testing will provide an accurate diagnosis. The next step is deciding how to address it.

“The solution largely depends on the timing and frequency of application, as the forms of S commonly found in fertilisers, sulphate S and elemental S, each have different properties,” explains Katie.

Sulphate S is plant available, but also vulnerable to leaching, especially if soil has a low anion storage capacity (ASC) and high annual rainfall (> 1500 mm).

Elemental S, on the other hand, isn’t plant available or vulnerable to loss by leaching, and is gradually converted by soil bacteria into plant available sulphate S. When these bacteria become more active in warmer soil temperatures, this conversion increases. 

“When choosing a product to deal with an S deficiency, you want to minimise potential S losses via leaching over winter,’’ says Katie. 

For spring application, sulphate S is generally best. However, if soils have poor S retention and experience high drainage, a mix of both sulphate S and elemental S is a better choice.

For autumn application, elemental S is preferred, as it’s resistant to leaching over the winter period, and remains in the soil to meet the S requirements of spring pastures, while also providing a slow release of S over the growing season.

Combining S with N fertiliser can ensure response to N fertiliser isn’t limited, and increase production compared to using N alone. PhaSedN Quickstart and SustaiN Ammo can be used to apply both nutrients in late winter to early spring, and PhaSedN is ideal for autumn application (see Table 1).

If phosphorus (P) is required to maintain levels within optimum, applying a product from the Sulphurgain range during autumn provides soluble P along with sulphate S for immediate plant uptake, and elemental S to support long term pasture requirements (see Table 1).

“The range of products make applying S more convenient, as it can be applied together with other nutrients, at the time that best suits you,” says Katie.