Sulphur Requirements of Winter Wheat (HGCA Topic Sheet No.31)

Sulphur Requirements of Winter Wheat

TS No.31
Winter
1999/2000



Action:

  • Check the location of your farm on the risk deficiency map. S deficiency is more likely to occur on light and medium textured soils.
  • Look for deficiency symptoms in spring yellow, younger leaves but greener, older leaves.
  • Consider testing whole plant shoot samples at early stem extension (GS 31-32) for S content. A critical value of less than 2 mg/g S indicates deficiency. Results may be available too late to correct deficiency in the current crop.
  • If deficiency is confirmed, apply 15 kg S/ha (37.5 kg SO3 /ha) as ammonium sulphate or other products containing sulphate before stem extension in early spring.

Extent of deficiency

This project work was led by IACR in collaboration with ADAS, Newcastle University and the Campden and Chorleywood Food Research Association.

Between 1995 and 1999, 14 field trials were carried out on 4 potentially deficient sites. Locations were Bridgets, Hampshire (chalk soil),Woburn, Bedfordhire (sandy soil), Raynham, Norfolk (sandy-loam) and sites in the Borders region (loam).

Yield responses to added S were significant in 4 trials (Table 1). Most of the yield increase came from the first 20 kg S/ha (Figure 1).

Comparison with earlier years data confirms that the extent of S deficiency in the UK is increasing year by year. Figure 2 indicates current deficiency risk based on soil type, proximity to coal-burning power stations, prevailing wind direction and rainfall.

Breadmaking quality

Sulphur affects the composition of grain proteins glutenin and gliadin, which are essential for well-risen loaves.

S application improved quality more often than yield. Early spring applications significantly increased loaf volume at all 4 sites, and in 6 of the 10 trials where the grain was suitable for breadmaking.

Loaf volume correlated more closely with grain S concentration than with grain N (protein). All varieties responded similarly to added S. Grain that was S deficient usually had N:S ratios above 16:1.

Using fertilisers

Pot and lysimeter trials were carried out at Rothamsted in collaboration with Stefes.

Fertilisers containing elemental S were relatively resistant to leaching, but were not readily plant-available. Non-flowable elemental S fertilisers should only be applied to cereals if autumn application is essential.

Ammonium sulphate and gypsum (calcium sulphate) were immediately available to the plant but leached very rapidly. In pot experiments, severe deficiency decreased grain yield mainly by reducing ear number/plant and grain number/ear. Additional S only increased yields if applied during stem elongation.

Spring applications produced the best responses in the field (Figure 3). Generally over 15 kg/ha S corrected deficiency. Effects of foliar ammonium sulphate applied at the milky-ripe stage on both yield and quality were inconsistent. Sometimes leaves were scorched and yields were reduced.

Plant symptoms did not always occur and are easily confused with nitrogen or manganese deficiency. Research is continuing on plant tissue testing as the basis for a field test.

Summary

Topic Sheet No.1 summarised HGCA-funded research results up to 1996 on effects of sulphur on wheat yields and presented a risk deficiency map for the UK.

In subsequent trials effects on grain quality were more frequent than on yield, sometimes in the absence of visual symptoms. The extent of S deficiency has continued to spread, with 25% of the UK wheat crop now at risk. Work is continuing on diagnosis of deficiency and forms of fertilisers.

Further information:

Prof Steve McGrath, IACR Rothamsted
Tel: 01582 763133

Project Report No. 197

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The Home-Grown Cereals Authority (HGCA) has provided funding for this project but has not conducted the research or written this report.While the authors have worked on the best information available to them, neither the HGCA nor the authors shall in any event be liable for any loss, damage or injury howsoever suffered directly or indirectly in relation to the report or the research on which it is based.

Reference herein to trade names and proprietary products without stating that they are protected does not imply they may be regarded as unprotected and thus free for general use. No endorsement of named products is intended, nor is any criticism implied of other alternative, but unnamed products.

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