Researchers from the CSIRO Agriculture Flagship and Kalyx Young focus on ways to reduce yield loss.

They state:

The period of grazing can increase net crop returns by up to $600-900/ha (i.e. 2000-3000 sheep grazing days at 28c/day) and have a range of systems benefits including weed management, reducing crop height and enabling pastures to be spelled during this period.

Both positive and negative effects on subsequent grain yield. Positive effects can occur under dry seasonal conditions where grazing reduces crop canopy and slows water use to be used later to fill grain more effectively.

When grazing stops sufficiently early this allows sufficient time for the crop to recover critical biomass and leaf area to achieve its similar grain yields to ungrazed crops

The authors provide the following take-home message:

• Timing of lock up and residual biomass influence grain yield recovery in both cereals and canola
• Early lock-up enables a crop sufficient time to achieve biomass levels at flowering to fully recover grain yield but lower residual biomass at lock-up can reduce crop recovery during a sensitive window around or shortly after GS30 in cereals and bud visible in Canola.
• Light defoliation with sufficient residual biomass even after GS30 can allow cereal crops to fully recover grain yield in some seasons.
• To avoid risk of yield loss in canola, residual biomass levels greater than 2.5 t DM/ha are required if grazing continues after late July. A similar critical level is less clear in cereals but appears to be about 1-1.5 t DM/ha required at lock-up in mid-August.