Options for frosted grain

The effect of frost on yield and quality of grain depends on the stage of crop development. In general as development progresses through grain filling the grains become drier and they become less frost susceptible. If affected during:

• flowering: the grain is aborted and yield is reduced but there are rarely any negative impacts on quality of remaining grain. * watery stage: grain does not develop any solids and frosted grains do not appear in the sample. Unfrosted grains can compensate and are often larger with high test weight.
• milk stage of development:  grains may continue to develop, but will be light and shrivelled. They usually have a low hectolitre weight and high screenings, but this can usually be minimised by adjusting header settings.
• late dough stage: can result in wrinkly/scalloped grains. Again, these may have a low hectolitre weight and higher screenings and further cleaning may be required. In frost damaged crops adjust header settings to maximise the quality of the grain harvested.

Harvesting

Frosted crops are difficult to thresh due to higher residual sugars in the straw and chaff, lower grain volume and high screenings. Despite lower tonnages, daily harvest maintenance and regular machinery clean down is vital to minimise machinery fatigue and fire risk in these difficult harvesting conditions. Frosted crops generate more dust and the crop residue builds up on the machine when harvested, contributing to increased fire risk. This is due to the tough nature of frosted stems, shattering of frosted grains and increased fungal growth on the crop. If practical to do so, harvest frosted paddocks last.

Grain quality may also be compromised depending on the timing of the frost event. Frost affected grains usually have a lower hectolitre weight and higher screenings. Adjusting header settings and/or grading can be beneficial but check the feasibility first.

Frosted stubble can also rot off at ground level and be difficult to seed into. To minimise trash flow problems in subsequent seasons, frosted stubbles may have to be cut low at or in a separate operation after harvest.

Marketing

Frosted grain is included in the category ‘Dry Green, Sappy and Frost Distorted’, for which there is a maximum limit of 1% in total. Grain containing over 1% but less than 10% frosted grain is classified as Australian General Purpose (AGP). Any grain exceeding this level will be classified as and suitable for stock feed. Higher classification of frost-affected grain may be achieved by cleaning grain but the capacity and economics of doing this need to be carefully considered.

Read the Managing frost risk tips and tactics fact sheet for more information.