Study shows importance of sulphur to OSR yields

Applying extra sulphur to oilseed rape crops delivered an extra £70/ha last season, according to ADAS trial results.

The ADAS run trial at Rosemaund, Herefordshire, showed an optimum sulphur rate of 112kg SO3/ha which increased yield from 3.93t/ha to 4.1t/ha. So, an additional £25 spend produced an extra £70 yield giving a 250% return on your investment.

Using DK Expower and DK Extrovert grown on the sandy loam site, the trial was designed to compare the crop’s response to sulphur with a range of rates from zero to 150kg SO3/ha and at two N rates. The lower N rate was sufficient to produce a 3.5t/ha crop with an additional 90kg N/ha for the higher rate, targeting 5t/ha crop.

Soil mineral nitrogen tests revealed there was just 9kg/ha of N and a further 27kg/ha to mineralise over the growing season. This added to the 38kg already in the crop gave a total soil nitrogen supply of 74kg N/ha. With OSR requiring a total N uptake of 175kg/ha to produce a 3.5t/ha crop, the amount of fertiliser N required, assuming a 60% uptake efficiency, was calculated at 212kg/ha.

“Growers don’t need me to tell them that 2012 has been a difficult year. Unfortunately this meant that we saw no effect from higher N rates so we were unable to prove our theory that higher yielding varieties will require higher sulphur inputs,” said Pete Berry, ADAS principal research scientist.

However, he added that unless there is a clear justification for not doing so, all rape crops will benefit from a sulphur fertiliser.

Allison Grundy arable agronomist at GrowHow added: “Lodging, the result of this year’s horrendous weather conditions, was the main factor restricting yield and preventing us testing our theory about higher sulphur rates in modern high yielding hybrids.

“However, it was interesting to note that there seemed to be a correlation between high S rates and lodging, even in the low N plots. We believe this is because sulphur helps the crop use N more efficiently so the high S, low N plots produced bigger crops which would normally have resulted in bigger yields.”

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