Management of lodging in winter wheat

With serious effects on yield and quality, it is important to predict and manage lodging risks. Use our lodging-risk calculator to help identify management options for your winter wheat crop.

A – Lodging resistance

The Recommended List (RL) provides a lodging resistance rating* for each winter wheat variety – with and without plant growth regulators (PGR). It uses a 1–9 score, where 9 indicates a high level of resistance to lodging. In the calculator, enter the without PGR rating.

However, it is important to note that resistance scores may effectively be reduced by:

• 1.0 – for each 5 kph increase in the maximum wind speed
• 1.0 – in a season with four extra days (compared with the farm’s average) when rainfall exceeds 7 mm
• 0.5 – for each 1 t/ha yield increase above 9 t/ha

Where no PGR is applied, varieties with a score 7 or less can be considered at particular risk.

*The RL rating system combines root and stem lodging. Specific data on root and stem lodging may be available from breeders.

B – SNS (soil nitrogen supply) index

Each unit increase on SNS index reduces the stem and root lodging resistance score by 1.5 and 0.75, respectively.

C – Sowing date

Early sowing often results in taller crops, with denser canopies and weaker stems – this increases lodging risk. For example, in Central England, a crop’s lodging resistance score increases by 0.5 for each week’s delay in sowing.

Note: Shallow drilling also increases lodging risk.

D – Plant population

Crops grown at higher plant populations have an increased risk of root lodging, due to reduced anchorage strength. Stem strength is also reduced to some extent. At plant populations of 200–400 plants/m², each increase of 50 plants/m² reduces the stem and root lodging resistance score by 0.5 and 1.0, respectively. Effects are greater below 200 plants/m².

Note: Sowing date adjustments are for central England. In northern Britain, treat score for 'End Sep' as zero.

Nitrogen

Early (pre–GS31) or excessive applications of nitrogen increase tiller numbers and reduce stem strength. When the canopy at GS31 is large (green area index of >2 or ground cover of >60%), lodging risk increases. Delayed and/or reduced nitrogen applications increase root and stem lodging resistance by 0.5 points. Where soil fertility is moderate or high, delaying the first nitrogen split is unlikely to affect yield.

Plant growth regulator (PGR)

Depending on the variety, a single PGR application can increase both root and stem lodging resistance by 0.5 to 1.5, respectively. PGRs are generally most effective in good growing conditions. Splitting applications increases the chance of matching application timing with appropriate growing conditions. Before use, always read the label and consult your buyer and/or processor. If in doubt, consult a BASIS-registered advisor.

Spring rolling

Loosely structured soils provide weak anchorage for crops. Spring rolling, in appropriate conditions, consolidates soils and can reduce root-lodging risk. Spring rolling before GS30 increases the root lodging resistance score by 1.0. However, rolling after GS30 can damage the growing point.

Use a metre ruler to measure the height from the ground to the top of the stem, base of ear or top of ear. Take an average of at least 10 shoots. Before GS39, the main stem (largest stem) of a plant should be measured but, after this, any tiller can be measured. The proportion of a crop that is lodged can be assessed from its first occurrence.

A percentage lodging index can be calculated:

Lodging Index = % Crop leaning (10° to 45° from vertical) ÷ 3 + % Lodging (>45° from vertical but not flat) ÷ 2 + % Lodged flat to ground