The results of a two-year survey has shown sulphur levels are low in many soils, and still falling, which could mean growers are failing to get the most out of their nitrogen fertiliser applications.
Carried out by Hutchinsons and Cobb Agri and published this week, the survey, which started in 2014 across farms in Herefordshire and Shropshire, showed only 13% of all crops sampled had a result in the normal range. All the others were low or slightly low.
Samples collected the following year showed 55% of crops had low sulphur levels triggering a high nitrogen: sulphur (N:S) ratio content of 16:1 or above.
Andrew Goodinson of Hutchinsons believes these results underline the extent to which soils are becoming depleted of sulphur, with detrimental effects on overall crop health.
“Sulphur is a fundamental nutrient needed for plant establishment, development and even crop maturity. It also helps to increase yield and protein within wheat.
“I always refer to the analogy of nitrogen being the building blocks for protein and growth, while sulphur is the mortar,” he explains.
Continuous intensive arable crops with high-yield crop varieties have depleted sulphur in the ground and at the same time atmospheric deposition is not occurring to maintain the sulphur levels, causing a sulphur deficiency.
The lower levels in 2015 are most likely a result of the high-yielding crops in the 2015 harvest which used up much of the nitrogen in the soil, upsetting the nitrogen:sulphur ratio.
“Given the close relationship between nitrogen and sulphur in plant nutrition, it’s crucial to address these low levels and to prevent underuse of any further nitrogen applications,” he says.
“The correct N:S ratio in the plant is critical to efficient nitrogen use.”
“A nitrogen:sulphur ratio of 12:1-15:1 is the normal range, and indicates adequate sulphur levels. However, if this goes up to 16:1 or 17:1, it indicates lower levels of sulphur. A reading of 18:1 would mean a low sulphur status and the need for a sulphur treatment for the next crop,” he says.