Reducing stubble load

Research has shown that by reducing stubble loads, there is a reduction in the severity and duration of frost events, resulting in less frost damage and better yields under frost conditions. No differences were observed between stubble height, orientation or composition. Data to date suggest it’s mainly a load issue.

Stubble reduction can be achieved by various management strategies including; cutting low, windrow burning/chaff carting, stubble mulching, raking and burning, strategic blanket burning and summer grazing. In terms of minimising frost risk, a good rule of thumb is that stubble loads should match target grain yield. For example, in a low production environment, 2 t/ha grain yield potential equates to 4 t/ha stubble remaining after harvest.

The stubble load needs to be halved prior to seeding, back to 2 t/ha to minimise frost risk. In a medium production environment, 3 t/ha grain potential equates to 6 t/ha stubble remaining after harvest. This can be reduced to 3 t/ha to manage frost risk. This calculation assumes a harvest index of 0.5. Current research shows that without frost, a once off stubble reduction (after opening rains at or just prior to seeding) did not reduce yield.

In the absence of frost, stubble reduction often gives a slight improvement in yield, due to reduced disease and less nitrogen tie up, depending on site, season and variety choice. With multiple severe frost events, stubble reduction does not increase yield in the most frost prone parts of the landscape but may in the moderately prone areas (Smith et al 2017).

Reducing the amount of stubble: stubble loads above 1.5 t/ ha in low production environments (2–3 t/ha) and 3 t/ha in high production environments (3–5 t/ha) generally increase the severity and duration of frost events and have had a detrimental effect on yield under frost.