Sulphur (S) - soil and crop
Definition
Sulphur (S) is an essential nutrient for soil fertility and crop growth. It is a key component in protein formation, making it particularly important for grass and forage crops that require large amounts of protein.
Importance
Adequate sulphur levels in the soil:
- Improve nitrogen utilisation, leading to better protein synthesis.
- Reduce nitrate accumulation in plants.
- Support higher dry matter yields.
Sulphur deficiency, similar to nitrogen deficiency, results in reduced growth and lower yields. Deficiencies are most common in the first cuts of the season.
Sulphur Supply and Decline
Sulphur availability has decreased significantly over the past decade due to:
- Lower industrial sulphur emissions.
- Limited use of sulphur-based fertilisers.
Current sulphur supply mainly comes from:
- Mineralisation of organic matter (primary source)
- Atmospheric deposition (precipitation)
- Capillary rise from deeper soil layers
- Animal manure
- Losses occur primarily through leaching.
Sulphur Content in Feed Products
- High sulphur content: Potato press fibre (>10 g/kg dry matter)
- Low sulphur content: Maize silage, CCM, pressed beet pulp
- Moderate sulphur content: Grass and grass silage (3–4 g/kg dry matter)
Sulphur content (g/kg dry matter); Eurofins Agro 2009-2013
| Fresh grass | Grass silage | Maize silage | Lucerne | |
| Average | 3.5 | 3.1 | 1.0 | 1.7 |
| Target range | - | 2.0-3.5 | 1.1-1.6 |
Key Considerations
- Monitor sulphur levels to optimise crop growth and forage quality.
- Apply sulphur fertiliser early in the season if SLV is insufficient.
- Balance sulphur with nitrogen for efficient nutrient utilisation.
Determining Sulphur Availability
The most important supply factor, mineralisation, can be assessed through an S-total determination using the Fertiliser Manager from Eurofins Agro. This analysis calculates the Sulphur Supplying Capacity (SLV), similar to the Nitrogen Supplying Capacity (NLV), for the first three cuts.
If SLV and other minor sources do not meet crop requirements, supplementary sulphur fertilisation is recommended, usually applied during the first two cuts to prevent shortages later in the season.
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