To compare and contrast plant growth regulation strategies in winter and spring barley germplasm.

• Under overhead irrigation in a relatively fertile rotation position (first barley after canola) the spring barley RGT Planet significantly out yielded the winter cultivar Cassiopee (10.07 vs. 8.98t/ha).
• Applying Moddus Evo at 400 ml/ha either as a single application (GS31) or split (GS31 & GS33) led to a significant increase in grain yield (9.87 – 9.92 t/ha) compared to the grazed or untreated plots (8.97 & 9.35 t/ha), averaged across both varieties.
• There was no interaction between variety and PGR application or grazing on plant height, lodging or yield indicating that both the spring and winter cultivar responded similarly.
• Cassiopee grew taller and was subject to significantly more lodging than RGT Planet.

• Both varieties showed positive responses to PGR applications of Moddus Evo (trinexapac ethyl) in terms of reduced crop height, lodging control and final grain yield.
• Grazing achieved a significant reduction in crop height (6cm) at harvest; statistically the same as the effect of Moddus Evo at either rate however it was associated with reduced yield and grain protein (data not shown).
• Grazing winter barley at GS30 produced significantly more dry matter than grazing spring barley that reached GS30 earlier in the winter (1928 vs 726kg DM).
• Unlike other trials conducted on cereals at the Finley site grazing did not reduce lodging in this experiment.
• A single application of Moddus Evo 400mL/ha at GS31 had significantly less lodging than the untreated plots.