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Sulfur deficiency has become more common as farmers moved from ammonium sulphate to sulfur-free urea, and from single super phosphate to sulfur-free DAP. It looks very similar to N deficiency but appears on the younger leaves first because S is not mobile in the plant.

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When rice is most vulnerable

From tillering through panicle initiation. S is needed for protein synthesis, so a shortage limits tillering, chlorophyll, and grain quality.

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How sulfur deficiency shows in satellite data

  • Low NDVI and NDRE similar to N deficiency, but the pattern is often not corrected by N top-dressing - a diagnostic sign in itself.
  • Uniform across the field if the whole field uses S-free fertilizer; patchy where S has been variably applied.
  • Confirm by contrasting with a small N-only test strip - if the strip does not green up, suspect S.

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Field symptoms

  • Pale-yellow to yellow-green young leaves (compare to N deficiency, where the older leaves yellow first)
  • Uniform yellowing across the whole leaf blade, not scorched edges
  • Reduced tillering and stunted growth
  • Delayed heading and reduced grain filling

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Reduce the damage by

  • Switch to a sulfur-containing fertilizer - ammonium sulphate, single super phosphate, or sulphate of potash instead of the S-free equivalents.
  • Apply gypsum (calcium sulphate) on chronically S-deficient soils - typically 100 to 200 kg per hectare.
  • Return crop residues and organic amendments - straw and manure contribute meaningful S.
  • Do not diagnose from color alone - N and S deficiency look similar; use an N test strip or leaf analysis to confirm.

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Set an alert for early warning

Turn the diagnosis into a trigger. Go to the Alerts page and configure a rule so a field that stays pale despite adequate N is flagged for a sulfur check.
Recommended settings for sulfur on rice:
  • NDRE threshold alert during tillering.
  • Manual review flag: if a field triggers a low-NDRE alert and the recent management log shows N top-dressing was already applied, suspect S (or Zn) rather than N.