Mark Tucker gives sulphur adivce in this Yara-sponsored article…
Sulphur applications have been discussed on many occasions over the last 15 years, but still confusion exists about how much and when to apply.
First a response is not seen on every site so a logical decision should be made as to its requirement. The most likely sites to give a response are the light free draining soils where little manure is used. Close proximity to industrial areas will also reduce your likely response.
Grain N:S ratio measurements can be used to help clarify the sulphur supply. Unfortunately sulphur is not free in fertilizer, typically costing between £8 and £10/ha, which must be more than recovered to make it a worthwhile investment.
In terms of yield an extra 2% in wheat (0.15 – 0.2 t/ha) roughly returns £2.25 for every £1 spent. To achieve this same return in oilseed rape then a 3% response is needed.
Trials data varies considerably not only from site to site, but also from year to year, thus predicting an expected yield response is not a precise science. Where factors are in favour of sulphur deficiency then yield increases will certainly be above those indicated.
In terms of the amount required then much of the research has been carried out on the most sulphur deficient sites i.e. light sands, and in these extreme cases the optimum sulphur required on oilseed rape was in the order of 75 kgSO3/ha and not the 120+kgSO3/ha often recommended. Yara’s own research has demonstrated that a good guide is 40-50kgSO3/ha on cereals and 60-75 kgSO3/ha rates on oilseeds.
Applying this in at least two applications will avoid the leaching risk associated with sulphur.