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Potassium regulates water, translocation of assimilates, and disease resistance in rice. K deficiency reduces grain filling, weakens stems (increased lodging), and increases susceptibility to sheath blight and brown planthopper. It is common where crop residues are removed and where high-yielding varieties are grown continuously without K replenishment.

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When rice is most vulnerable

From active tillering through grain filling. K demand is highest around panicle initiation and again during grain filling.

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How potassium deficiency shows in satellite data

  • Later-season NDVI decline while the crop still has weeks to grain-fill - the canopy senesces early. The decline itself is expected: every ecosystem band on Rice Ecosystems drops sharply at ripening because the crop is moving nitrogen and sugars into the grain. What marks K deficiency is when it starts — a decline that begins before the ripening window opens for that ecosystem, while the field is still at panicle initiation, booting or heading. The platform derives that window from the establishment date, so the comparison is against the field’s own phase rather than the calendar. A decline that starts inside the ripening window is the band behaving normally and is not a K finding.
  • NDRE stays lower than expected at booting despite adequate N inputs.
  • Signature overlaps with drought and late-season N depletion; separate with weather history, soil K status, and leaf-margin symptoms on the ground.
  • Increased lodging appears as flat patches in the late-season imagery.

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Field symptoms

  • Yellow-brown scorching along tips and margins of older leaves, progressing inward
  • Small brown spots (“bronzing”) on older leaves, sometimes confused with brown spot disease
  • Weak, slender stems and increased lodging
  • Higher incidence of sheath blight and stem borer damage
  • Poorly filled grains, high percentage of unfilled spikelets

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Reduce the damage by

  • Split K application - basal plus a top-dressing at panicle initiation gives more consistent results than a single basal dose.
  • Return rice straw or apply compost - straw is the cheapest large-scale K source available on-farm.
  • Correct K especially on sandy, degraded, or intensively cropped soils and on sodic soils where K uptake is impaired.
  • Balance K with N - high N without matching K worsens lodging and disease.
  • Match K to yield target - high-yielding hybrids remove more K per hectare than traditional varieties.

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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 late-season canopy decline is caught while there is still time to apply a K top-dressing at panicle initiation.
Recommended settings for potassium on rice:
  • NDVI drop alert in the two weeks around panicle initiation - trigger on a drop of 0.08 or more.
  • NDRE threshold alert during booting - trigger when NDRE falls below the fertile-strip reference.