Soil and tissue analyses for sulphur show that many growers are still not applying sufficient sulphur to avoid risking yield and quality losses.
The results of 6 years’ soil and tissue analysis have shown that with the long term trend of sulphur deficiency in soils continuing, many growers, whilst more aware of the problem, are still not applying sufficient sulphur to avoid risking yield and quality losses.
Undertaken by Lancrop Laboratories from 2011, up to and including 2016, soil results revealed that sulphur levels in soils growing both wheat and oilseed rape are nearly 100% deficient .
"Plants need sulphur to be able to use nitrogen efficiently,” says Natalie Wood, Yara Agronomist, “so having sufficient sulphur is essential to avoid detrimental effects on crop health, quality and yield losses. Whilst this is a message that is becoming increasingly understood, there is still more to be done.”
Long term sulphur deficiencies
The analyses by Lancrop Laboratory on soils under a range of cropping clearly show the long term increase in soil sulphur deficiency over the last six years with the number of wheat fields low in sulphur increasing from 88% in 2011 to 97% in 2016.
“Whilst the long term trend is clear results in soil can vary from season to season due to the fact that sulphur is mobile in soil and will leach,” says Ms Wood, “This means that results will depend on weather and also levels of cropping - with 2015’s excellent harvest being responsible for removing nitrogen, and with it sulphur, from the soil.”
The overall trend is clear with long term results in wheat showing a deficiency from 63% in 1995 to almost total deficiency (97%) 21 years later.Increasing awareness With soils nearly 100% deficient in sulphur, only sulphur applied by growers will be shown in leaf samples and plant tissue analysis has shown an increasing awareness of the benefits of applying sulphur with 55% of wheat samples being recorded as normal in 2016 compared to just 31% in 2011.
“Research has confirmed this trend by showing that the areas of wheat receiving sulphur rose from 46% in 2011 to 62% in 2015,” said Ms Wood. “This is potentially due to growers trying to get better yields and increase grain quality. In oilseed rape, where sulphur offers a range of benefits from better crop establishment to improved grain yield and oil content of seed the percentage was higher and increased from 70% to 73%. Whilst this shows that there is more attention being paid to sulphur in OSR than in cereals, many growers are still not applying sufficient sulphur and risk a loss of yield and quality.”
Sulphur should be considered a major nutrient
20 years ago, sulphur dioxide emissions from industrial origins guaranteed a sufficient supply of sulphur and deficiencies were rare. Now, with stricter environmental regulations, including reduced emissions from low sulphur fuel – soil receives fewer automatic sulphur deposits. In the last 40 years the amount of sulphur deposition has dramatically decreased from approximately 6.4 million tonnes to around 0.5 millions tonnes in 2008.
At the same time, continuous intensive cropping, and the development of high yielding varieties, has contributed to the depletion of nutrients in the ground, notably sulphur.
“Until recently sulphur has been considered a secondary nutrient,” concludes Ms Wood, “now, however, it is very much a major nutrient, considered by many agronomists to be the second most important nutrient after nitrogen. Yara field trials confirm that the correct strategy for application is ‘little and often’ applying multiple, smaller, applications in line with crop demand through March, April and May, coincidental with the splits of nitrogen. In cereal crop trials this strategy has produced yield increases of 0.3 t/ha whilst in oilseed this has been higher at 0.5 t/ha.”
Recommended Sulphur Fertilizers
The following fertilizers are recommended for all crops and supply a combination of nitrogen and sulphur (N+S) in appropriate ratios to allow the ideal timing for application of both nutrients.