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Identifying and correcting site-specific sulphur deficiency

Patrick Forrestal1, Karen Daly1, Guy Serbin1, David Wall1, Paul Murphy2

1Teagasc Environmental Research Centre, Johnstown Castle, Wexford.  2 University College Dublin,

Background

Sulphur (S) is an essential nutrient for plant growth occurring in the major amino acids, cysteine and methionine and playing a critical role in protein synthesis and photosynthesis. Higher yielding crops require greater levels of S nutrition to maintain optimum yield, protein content and high nitrogen use efficiency. Plants mainly take up the divalent anion sulphate (SO4) through roots. However, more than 95% of soil S occurs in non-plant available, largely organic, forms. Studies in the 1970’s and 1980’s found grassland yield responses to S at 71 of 139 Irish sites. 

Since the 1970’s and 1980’s,

  • Atmospheric S deposition has reduced due to emission controls
  • Crop yields have increased through genetic gain and better management leading to increased S demand

These factors highlight the risk that S limitation in Ireland may now be more widespread than it was in the 70’s and 80’s. In the context of sustainable intensification of Irish agriculture, which depends on efficiently increasing yields, optimization of S nutrition is more important than ever. Yet this nutrient has received little attention compared to nitrogen and phosphorous.

Figure 1. S responsive and non-responsive sites in work conducted in the 1970’s and 1980’s (Murphy and Boggan, 1988)

Objectives of current work

  • Detail the changes in S deposition in Ireland since the 1980’s
  • Evaluation of grass yield, protein quality and nitrogen use efficiency response to S on a range of contrasting soils managed at high intensity.
  • Development of soil and plant based tools for identifying S deficiency risk and site-specific S deficiency

Figure 2. Optical sensing and hand held x-ray fluorescence testing

  • Linking soil based parameters with national mapping efforts by the Soil Information System and Tellus to develop deficiency risk maps

Figure 3. Developing and existing soil parameter mapping: Tellus soil S (top), Irish Soil Information System (bottom)

  • Evaluation of a range of existing and novel S fertilization strategies in Irish grassland.

Figure 4. Selection of sulphur sources for agriculture

Expected benefits

This project will provide much needed knowledge on the relationship between soil characteristics, geo-chemical parameters and agronomic response to S for Irish soils. This knowledge could be increasingly useful in conjunction with new ongoing national mapping of soils. Diagnosis of S deficiency can be challenging. This project will contribute to the development of soil specific S nutrition advice and, additionally, site-specific diagnosis of yield reductions due to S deficiency using plant based measurements. The results of this work are expected to contribute updates to national S fertilization advice.

Acknowledgements

We acknowledge financial support from the Walsh fellowship programme for funding the Ph.D student to be taken on in this project.

References

Murphy, M.D. and Boggan, J.M. 1988. Sulphur deficiency in herbage in Ireland : 1. Causes and Extent. Irish Journal of Agriculture and Food Research, Vol. 27 No. 1, pp 83-90.