Sulphur (S) is one of those nutrients that rarely gets the attention of Nitrogen (N) or Phosphorus (P), but it quietly limits pasture performance across many New Zealand farms. It plays a key role in protein formation and is closely linked to N use and utilisation. If S is in short supply, plants cannot fully utilise N – whether it is from fertiliser or clover fixation. This is why S is important in ryegrass–clover systems, where clover drives pasture quality and total production.
Most New Zealand soils are naturally low in S, and do not receive large atmospheric inputs. Historically, regular applications of superphosphate were adequate for maintaining S levels, but as fertiliser choices changed over the years, deficiencies are more common.
One of sulphur’s biggest challenges is how it behaves in the soil. The plant-available form, sulphate, is very mobile and easily leached. This is especially true in free-draining soils like pumice and sands. In these environments, S does not hang around long, so regular inputs are needed to maintain supply. At the same time, most S in the soil sits in organic matter and is only released through mineralisation. Soil biology, temperature, and moisture all influence how much becomes available. Cool, wet conditions slow the release and increases the risk of deficiency just as growth demand rises.
Sulphur deficiency often shows up as pale, slow-growing pasture, and can be mistaken easily for N deficiency. A key indicator is the deficiency will express on the new growth coming through, instead of the old growth, like a N deficiency. However, herbage testing is recommended to properly identify the issue.
From a management perspective, both form and timing of fertiliser matters. Sulphate S gives a quick response but is prone to loss; elemental S provides a slower, more sustained release as it oxidises in the soil. Many programmes use a mix of both to balance immediate and longer-term supply. Typical S requirements sit in the range of 30 to 50 kg S/ha annually, but this depends heavily on soil type, rainfall, and system intensity. Higher leaching environments or intensive systems generally sit at the upper end.
Your key takeaway? If pasture response is not matching N inputs, or clover is not pulling its weight, S is worth a close look. It may not grab headlines, but getting S right is essential for maintaining pasture performance and making the most of your fertiliser investment.
TECH TIPS
- Regular soil testing helps you understand the effectiveness of your fertiliser programe and shows the long-term fertility trends across your farm. However, before soil testing, ensure no phosphate and potassium fertilisers have been applied in the previous three months as this can lead to elevated test results.
- Protect soils from pugging damage. Graze wet paddocks early before soil moisture gets too high.
