Essential nutrient contributing to 0.2-0.5% of a plants nutritional makeup
Involved in protein formation, photosythesis oil production and increasing nitrogen utilisation
Deficiency symptoms include yellowing of younger leaves and pale flowers in oilseed rape
Sulphur is vulnerable to leaching losses due to its high mobility in the soil
Best applied little and often alongside nitrogen applications to maximise performance
Sulphur containing products include Ammonium sulphate (60%), Polysulphate (48%), Kieserite (50%) and Sulphate of potash (45%)
Sulphur is held in several mineral forms in the soil, with sulphate (SO4-) and sulphide minerals being most common. Sulphate is the form most easily taken up by the plant roots but, like nitrate (NO3-), it is also very mobile in the soil and is prone to leaching particularly in light, sandy soils. This is due to its negative charge which means it is unable to bind to clay particles which also have a negatively charged surface.
Most soil sulphur is present in organic matter and can be released into plant available forms once mineralised into sulphate. The quantity of sulphur mineralised from organic matter in a typical UK soil is around 5-10kg/ha/yr on average.
The atmosphere contains varying amounts of hydrogen sulphide (H2S), sulphur dioxide (SO2), carbonyl sulphide (COS) and other sulphur gases which are produced primarily from industry - in particular fossil fuel production.
Since the 1980s, the atmospheric air pollution of sulphur has declined to below 10% of what it was just 50 years ago, and this has greatly reduced the natural deposition of sulphur onto UK soils, resulting in a greater need for sulphur fertilisation.
Sulphur deficiency is becoming more widespread due to a reduction in the use of fossil fuels which has led to lower levels of atmospheric deposition.
Plants deficient in sulphur have pale green or yellow younger leaves. Despite being mobile in the soil, sulphur is fairly immobile in the plant and so - unlike nitrogen - the younger leaves are the first to show signs of deficiency.
In sulphur deficient oilseed rape, flowers look pale and interveinal yellowing occurs in the middle and upper leaves.
A Broad Spectrum (BS) soil analysis can help determine the quantity of sulphur within the soil which is likely to be available for crop uptake and can be used to help tailor fertiliser plans and to help prevent deficiencies within the season.
Tissue testing is also useful to determine the sulphur concentration of the plant mid-season in order to compare against optimum levels. Assessing the N:S ratio within the plant can help highlight a potential deficiency. Although laboratory results may be available too late to correct the deficiency in the current crop, they can be useful for decisions on sulphur use for future crops.
Sulphate (SO4-) is soluble in the soil solution and is not held on soil particles. Once the soil is fully wetted, sulphate may leach into field drains or subsurface aquifers as drainage water moves through the soil. The amount of winter rainfall has an important influence on the amount of sulphate leached.
Products containing sustained release sulphur can help mitigate the risk of sulphate leaching, particularly on light, sandy soil and in areas of high rainfall. Given its ability to improve nitrogen use, it is advisable to apply sulphur alongside nitrogen applications at a ratio of 12kg nitrogen per 1kg sulphur.
Best applied little and often in the spring when crops are actively growing.
Avoid applying large rates of readily available sulphur to light, sandy soils or in areas of high rainfall to avoid potential nutrient loss.
Total sulphur application rates depends on crop type, soil type, estimated yield and the end market. Consult RB209 or your local Nutrition Agronomist for more details.
Avoid applying large rates of sulphur to light, sandy soils or in areas of high rainfall to avoid potential nutrient loss.
Total sulphur application rates depends on crop type, soil type, estimated yield and the end market. Consult RB209 or your local Nutrition Agronomist for more details.
Fertiliser | Analysis | Features |
---|---|---|
Ammonium sulphate | 21-0-0 + 60SO3 | A high sulphur nitrogen source made by reacting ammonia with sulphuric acid |
Polysulphate | 0-0-14 + 6MgO + 48SO3 + 17CaO | High sulphur multi-nutrient containing sustained release sulphur. Mined from natural rock deposits. Organic certification. Low chloride. |
ESTA Kieserite | 0-0-0 + 25MgO + 50SO3 | Highly soluble magnesium and sulphur fertiliser mined from natural salt deposits. Organic certification |
Sulphate of potash (SOP) | 0-0-50 + 45SO3 | A manufactured granular potash containing high levels of sulphur |
Origin Sulphur-N | 26-0-0 + 35SO3 | High quality NS compound |
PotashpluS | 0-0-37 + 2.8MgO + 23SO3 + 8CaO | A multi-nutrient granular fertiliser comprising MOP and polysulphate |
Korn-Kali | 0-0-40 + 6MgO + 12SO3 + 4Na2O | A multi-nutrient granular fertiliser mined from natural rock deposits. |
Origin 27N range | 27-0-0 + 9SO3 27-0-0 + 10SO3 27-0-0 + 12SO3 | A high quality NS compound |