Lodging Risk & Get the Safe N and PGR Call
Scores wheat
Will your cereal lodge? Combine variety standing power, N rate, height, population, anchorage and windinto a 0–100 lodging-risk index with the dominant driver, the max safe N rate, the yield loss if it goes flat, and the PGR benefit.
Crop & agronomy
Runs in your browser — nothing uploaded. Framework after AHDB cereal lodging risk & Berry et al. (2004).
What is driving the risk
Next: cut risk now: cap N at about 153 kg/ha, apply a PGR program (22 points off), and avoid pushing population. The dominant driver here is variety standing power — fix that first.
Risk index after the AHDB Wheat & Barley lodging-risk framework (weighted driver checklist) and the biomechanical logic of Berry, Sterling, Spink et al., 'Understanding and reducing lodging in cereals' (Advances in Agronomy 84, 2004). Index is a planning score; actual lodging also depends on rainfall on the canopy, disease and exact stem geometry.
Lodging risk — key facts
- Low risk
- index under 30
- Medium risk
- index 30–60
- High risk
- index 60+
- Standing power
- 1 (weak) to 9 (stiff)
- Wheat N optimum
- ≈ 180 kg N/ha
- CCC + trinexapac PGR
- ≈ −22 risk points
- Yield loss if lodged
- ≈ 20–35%
- Lodging type
- stem (buckle) or root (anchorage)
- Index
- drivers − PGR, capped 0–100
- Privacy
- Runs in your browser; nothing uploaded
Cereal lodging-proneness reference
Base proneness, the wind speed at which a moderate canopy tips, the reference height, and the typical yield loss when fully lodged.
| Cereal | Base proneness | Critical wind (m/s) | Ref height (cm) | Yield loss if lodged |
|---|---|---|---|---|
| Winter wheat | 12 | 17 | 90 | 30% |
| Winter barley | 15 | 15 | 95 | 25% |
| Spring barley | 11 | 16 | 80 | 20% |
| Rice (paddy) | 16 | 12 | 100 | 35% |
| Maize (corn) | 10 | 20 | 230 | 25% |
| Oats | 14 | 14 | 110 | 22% |
PGR options and the points they remove
| PGR | Active | Points removed | Note |
|---|---|---|---|
| Chlormequat (CCC) | chlormequat chloride | −12 | Shortens lower internodes; the classic early PGR for wheat. |
| Trinexapac-ethyl | trinexapac-ethyl | −16 | Strong stem-shortening at GS31–32; widely used in barley and wheat. |
| CCC + trinexapac (program) | chlormequat + trinexapac | −22 | A split program gives the largest height/strength reduction. |
| Ethephon | ethephon | −14 | Late PGR shortening upper internodes; reduces ear-leverage lodging. |
| Prohexadione-Ca | prohexadione-calcium | −13 | Stiffens straw; common in barley and oats. |
Points are an index device reflecting typical height/strength reductions; follow the product label and local agronomy for timing and rate.
Lodging is wind leverage against stem and root strength
A cereal lodges when the bending moment from wind on the canopy — amplified by plant height and the weight of the grain head — exceeds either the stem's bending strength (stem lodging) or the root plate's ability to hold the plant upright (root lodging). Every management factor either raises that leverage or weakens the resistance: high nitrogen builds a tall, top-heavy canopy; a weak-strawed variety has thin stems; a dense stand etiolates them further; and loose, wet soil lets the roots pull out.
This calculator turns those drivers into a single 0–100 index and names the one that matters most for your field, so the fix is obvious — cap nitrogen, choose a stiffer variety, apply a PGR program, or firm up rooting. Use it alongside the GDD-to-Maturity and Crop Heat Unit tools to plan the season, and the Crop Yield Estimator to value the yield you protect by keeping the crop standing.
How to use it — 5 steps
- 1
Pick the cereal
Select wheat, barley, rice, maize or oats; the tool loads base proneness and reference height.
- 2
Enter variety & agronomy
Add standing power (1–9), nitrogen rate, plant height and population.
- 3
Add soil and wind
Set root anchorage and the wind speed expected in the lodging-risk window.
- 4
Read the index and driver
See the 0–100 score, the low/medium/high class, and which driver dominates.
- 5
Act on the call
Apply the max safe N rate and choose a PGR program if the score is medium or high.
Frequently Asked Questions
Will my wheat lodge this season?+
It depends on the balance between the wind's leverage on the canopy and the stem's strength plus the root plate's anchorage. This tool combines variety standing power, nitrogen rate, plant height, population, anchorage and expected wind into a 0–100 lodging-risk index: under 30 is low, 30–60 medium and 60+ high. A high score means the crop is expected to lodge at a normal seasonal wind, so it tells you the dominant driver to fix and the max safe N rate.
What is the safe nitrogen rate to avoid lodging?+
The calculator solves for the N rate that keeps the index just below the high-risk threshold, holding your other inputs fixed. Excess nitrogen above the crop's optimum (around 180 kg N/ha for winter wheat) builds a tall, leafy, top-heavy canopy that lodges, so the safe rate falls as standing power drops, height rises or anchorage weakens. Splitting N and avoiding a large late dose also lowers risk for the same total.
How much does a PGR reduce lodging risk?+
A plant growth regulator shortens and stiffens the straw, lowering the canopy's centre of gravity. In the index, chlormequat (CCC) removes about 12 points, trinexapac-ethyl about 16, and a CCC-plus-trinexapac program about 22 — enough to move many crops down a whole risk class. PGRs are most valuable on weak-strawed varieties grown at high N, and least useful when the real problem is poor root anchorage.
What is the difference between stem lodging and root lodging?+
Stem lodging is the straw buckling, usually low on the plant, when the bending stress from wind and head weight exceeds the stem's strength. Root lodging is the whole plant leaning over because the root plate fails to hold in the soil, which is common on loose or wet ground. Stem lodging is fixed mainly with PGRs and stiffer varieties; root lodging is fixed with better rooting, firmer seedbeds and not over-loosening soil.
Is a lodging risk index of 70 high?+
Yes. On the 0–100 scale used here, 60 and above is the high-risk band, so 70 means the crop is expected to lodge at an ordinary seasonal wind. At that level you should act: cap nitrogen at the calculated safe rate, apply a PGR program, and check whether population or anchorage is the dominant driver. Leaving a score of 70 unmanaged risks the 20–35% yield loss that full lodging typically causes.
What is variety standing power?+
Standing power is a variety's published lodging resistance, usually on a 1–9 scale where 9 is very stiff-strawed and 1 lodges readily. It captures inherited stem strength and height. In the index, each point below 9 adds about four risk points, so choosing a stiff variety is one of the cheapest ways to cut lodging risk before any spray decision.
How does plant height affect lodging?+
Lodging is a leverage problem: a taller plant puts the same wind force and head weight further from the base, so the bending moment at the stem and the pull on the roots both rise with height. The index adds about four points per 10 cm above the crop's reference height. That is why short-strawed varieties and PGRs, which lower height, are so effective.
Does a thicker stand lodge more?+
Generally yes. High plant populations produce thinner, more etiolated stems that are individually weaker, and a dense canopy intercepts more wind. The index adds risk above a reference of around 200 plants/m². Very thin stands can also lodge if individual plants grow tall and lush, so the goal is a moderate, even population matched to the variety.
How is the lodging risk index calculated?+
The index sums weighted points from each driver — crop base proneness, variety standing power, nitrogen rate, plant height, population and root anchorage — then subtracts the points removed by any PGR, capped at 0–100. The structure follows the AHDB cereal lodging-risk framework's weighted checklist combined with the biomechanical leverage logic of Berry et al. (2004), where wind force versus stem and root strength sets the outcome.
At what wind speed will my crop lodge?+
The tool estimates the wind speed at which your specific canopy tips, scaling each crop's critical wind by how your index compares to a moderate canopy. A low-risk, stiff, short crop may hold past 18–20 m/s, while a high-risk tall lush crop can go over at 10–12 m/s. Rain on the canopy and a soaked root plate lower these figures further, so treat the estimate as the dry-canopy case.
Can I still get yield with a high lodging risk?+
You can, but the expected yield loss if the crop actually lodges is large — roughly 20–35% for cereals lodged at or after flowering, plus harvesting difficulty, grain quality loss and drying cost. The point of managing risk is that the cost of a PGR and a sensible N cap is small against that loss, so reducing a high score to medium is almost always worthwhile.
What is the dominant driver and why does it matter?+
The dominant driver is the single input contributing the most risk points — often nitrogen rate or weak variety standing power. It matters because the cheapest, most effective fix targets that driver: if N is dominant, cut or split it; if standing power is dominant, a PGR or a stiffer variety helps most; if anchorage is dominant, no spray fixes it and you must address rooting and seedbed firmness.