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Cotton PGR (Mepiquat) Rate Calculator
Check plant vigor with height-to-node ratio (HNR) and get a starting mepiquat rate range by growth stage.
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How it's calculated
Height-to-node ratio (HNR) = plant height (in) ÷ number of main-stem nodes. HNR is the standard vigor check for cotton PGR timing: a stretchy, vigorous plant has a high HNR and needs mepiquat to hold internode length in check; a stocky, stressed plant needs none.
| HNR | Vigor | Typical rate* |
|---|---|---|
| < 1.5 | Normal to low | Hold |
| 1.5 – 2.0 | Borderline | 0–4 oz/ac |
| 2.0 – 2.5 | Vigorous | 4–8 oz/ac |
| > 2.5 | Excessive | 8–12 oz/ac |
*Scaled up slightly for later bloom stages, when cotton is most responsive to mepiquat. Actual programs vary by variety, planting date, moisture and regional guidance — this is a starting point, not a prescription.
Row Wise tracks plant vigor from drone canopy growth or satellite NDVI trend automatically, and flags when a field is trending toward an aggressive PGR program — before you have to walk it.
Get notified at launch →Frequently asked questions
What is height-to-node ratio (HNR) in cotton?
HNR is plant height in inches divided by the number of main-stem nodes. It's the standard field measure of cotton vigor used to decide whether — and how much — mepiquat chloride (PGR) to apply.
What HNR triggers a PGR application?
Many programs start considering an application around HNR 1.5–2.0, with more aggressive rates above 2.0–2.5. Below about 1.5, the plant isn't vigorous enough to need a PGR yet.
Does growth stage change the PGR rate?
Yes — cotton is generally more responsive to mepiquat during bloom, so the same vigor level often gets a slightly higher rate at first bloom or peak bloom than at match-head square.