Does crop nutrition influence frost risk?

As winter progresses, growers become increasingly aware of the risk of frost damage to crops at varying stages of development. The susceptibility of wheat to frost damage starts rapidly increasing after stem elongation (Zadock Growth Stage 30-39). It does not reduce to low risk until the end of the dough development grain fill stage (ZGS 80-89). If the crop canopy is wet from rain, frost damage can become worse. Growers frequently ask which factors have the greatest influence on the risk of frost damage.The GRDC Frost – Frequently Asked Questions guide looks at how factors such as crop variety, yield potential, stubble load and soil amelioration can impact frost severity.

Nutrition status

There has been much research into the relationship between crop nutrition status and the severity of frost damage. To date there is no strong evidence that nitrogen (N) softens wheat to frost. Trials in 2016 in WA concluded that managing wheat varieties had a greater impact on frost risk than varying nitrogen and seed rates. But high N rates may increase the synchronisation of canopy development, head emergence and flowering. If more of the canopy is flowering when a frost event occurs, the risk of damage to more of the crop increases. Do not target high yields by increasing N rates in frost prone paddocks. Crop potassium (K) status is important for reducing the impact of crop stress on grain yield. K deficiency results in poor water use and uptake of other nutrients, making crops more susceptible to drought, waterlogging, sodicity, salinity, frost and leaf diseases. Research by Murdoch University’s Dr Richard Bell showed higher levels of internal K (1.7-2.5 % K) in plants increases tolerance to frost damage and reduce frost-induced sterility in wheat. This is especially true for crops on marginal light sands with soil K levels below 50ppm. But extra K could not alleviate severe frost damage, resulting in more than 70 % sterility. The symptoms of copper (Cu) deficiency are similar to frost, often leading to misdiagnosis as frost damage.A youngest emergence blade (YEB) test will distinguish the two conditions, as YEB levels below 1.5mg/kg indicate Cu deficiency. Adequate Cu levels do not appear to influence frost damage in crops. Originally published by Communities GRDC.

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