Controlling transplant shock increases lettuce yields

Trial set up copy

Transplant shock is the reduction in growth that occurs when seedlings are transplanted from a container into the field.

This project showed that drenching lettuce seedlings with potassium nitrate at transplanting could increase yields by 20%.

Why study this?

Significant transplant shock can cause poor plant stands and a lower percentage cut of good quality lettuce at harvest. Blindness in lettuce causes multiple heading in mature plants, rendering the lettuce unsalable.

What was done

AHR researchers applied a potassium nitrate solution as a drench to seedlings of cos (cv. Quintas) and iceberg (cv. Toscanas) lettuce just before they were transplanted into the field at a commercial lettuce farm in Sydney.

Plants were assessed at four and seven weeks (commercial maturity) after transplanting and head fresh weights were recorded.

What we found

Potassium nitrate drenching resulted in larger plants four weeks after transplanting. The potassium nitrate treatment resulted in a 25% increase in shoot fresh weight compared to the control when applied to iceberg lettuce (cv. Toscanas) and a 22% increase in fresh weight in cos lettuce (cv. Quintus), four weeks after transplanting—both statistically significant.

At the harvest stage, the head weights of drenched iceberg lettuce plants were 19% higher, and cos lettuce 12% higher than the control plants. Again, both statistically significant.

Where to next

The researchers plan to expand their study to other treatments, such as controlling lettuce pests like lettuce aphids.


A fact sheet on controlling transplant shock in lettuce is available here

The final report for VG12017 is available here

For more information contact

Gordon Rogers, Applied Horticultural Research