Paddock planning key part of effective frost management
Identify paddocks or areas that are frost prone on your farm
Paddocks or areas in paddocks that are prone to frost can be identified through past experience, the use of precision tools such as topographic, electromagnetic and yield maps and temperature monitors to locate susceptible zones. This can help determine the appropriate management practice to use to mitigate the incidence of frost. Be aware that frost-prone paddocks can be high yielding areas on a farm when frosts do not occur. Once the farm has been zoned you can consider crop and variety selection.
- Pre-season checklist for mitigating frost risk with Ben Biddulph
- Sowing strategies and site elevation
- Frost mapping a future management tool
- Paddock selection and the importance of considering elevation
Frost zone management tactics
Consider enterprise in frost prone areas
The use of identified frost zones should be carefully considered, for example using them for grazing, hay or oat production and avoiding large scale exposure to frost of highly susceptible crops like peas or expensive crops like canola. It may be prudent to sow annual or perennial pastures on areas that frost regularly in order to avoid the high costs of crop production.
Review nutrient management
Targeting fertiliser (nitrogen, phosphorus, potassium) on high risk paddocks and seed rates to achieve realistic yield targets should minimise financial exposure, reduce frost damage and increase whole paddock profitability over time. These nutrients could be reallocated to lower risk areas of the farm.
While high nitrogen (N) increases yield potential it will also promote vegetative biomass production and increase the susceptibility of the crop to frost. Using conservative N rates at seeding and avoiding late top-ups results in less crop damage. It is best if crops are not deficient in potassium or copper, as this may increase susceptibility to frost events. This can be assessed from initial soil tests and with plant tissue testing.
Copper deficiency can be ameliorated with a foliar spray pre-flowering and as late as the booting stage to optimise yield, even in the absence of frost.
Potassium plays a role in maintaining cell water content in plants, which can potentially influence tolerance to frost. It has been shown that plants deficient in potassium are more susceptible to frost. Soils that are deficient in potassium could benefit from increasing potassium levels at the start of the growing season. However, it is unlikely that there will be a benefit of extra potassium applied to plants that are not potassium deficient.
Frost tolerance cannot be bought by applying extra potassium or copper to a crop that is not deficient. There is no evidence that applying other micronutrients has any impact to reduce frost damage.
Modify soil heat bank
The soil heat bank is important for reducing the risk of frost. Farming practices that manipulate the storage and release of heat from the soil heat bank into the crop canopy at night are important to consider to reduce the impact of a frost event.
Agronomic practices that may assist with storing heat in the soil heat bank include:
- Practices that alleviate non-wetting sands, such as clay delving, mouldboard ploughing or spading, have multiple effects; these include increasing heat storage, nutrient availability and infiltration rate.
- Rolling sandy soil and loamy clay soil after seeding can reduce frost damage. It also prepares the surface for hay cutting should it be necessary.
- Halving the normal seeding rates can reduce frost severity and damage by creating a thinner canopy and more tillers resulting in a spread of flowering time. However, weed competitiveness can be an issue.
- Cross-sowing/seeding. Crops sown twice with half the seed sown in each direction have a more even plant density. Heat is released from the soil heat bank more slowly to warm the crop canopy at head height in early morning when frosts are more severe. This practice, however, increases sowing costs.
Useful tools in understanding frost and the risk in different regions
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