Sifting needs from maps by Guy Cotsell

Above: The Veris 3100 measures the conductivity in soil using rolling disc electrodes. Measurements are taken at a similar spatial scale to that of a yield monitor. Left: Crop yield map showing manageable spatial patterns in variability.

FARMERS THEMSELVES can play a vital role in weighing strategies to reduce frost losses, according to a new report commissioned by the GRDC.

Researchers with ConsultAg, a WA consulting group, recommended large-scale field testing using farmer-scale machinery with participation by growers.

"Large-scale trials carried out with interested farmers or farmer groups, supported by technical specialists and temperature monitoring equipment, could go a long way in evaluating some of the theoretical frost avoidance strategies,"

said consultant Garren Knell. "This is very important because the thermodynamics of small plot trials may vary greatly from field conditions."

Mr Knell suggested that trials could include:

  • wide rowspacings-promising results showed that sowing at 36 cm spaced rows raised the air temperature at head height by 1-2°C
  • removing stubbles - retention of stubble mulch may prevent soil from radiating heat at night, which can cause colder temperatures at head height during the night. Mulches reduce· the thermal conductivity of soil so that the temperature of air over mulches is more variable than adjacent normal soil surfaces. As well. mulches usually prevent capillary rise susceptibility. There have been reports. for example. that crops on sandy paddocks treated with potash appear more frost-tolerant. while crops in parts of paddocks treated with high rates of nitrogen have been more severely frosted.
  • sowing up-slope rather than across the slope to encourage cold air drainage
  • mixing varieties of different height and flowering times
  • the effect of claying - applying clay to sandy soils could help heat absorption by darkening the soil. Claying is also said to lead to more moisture being retained at the soil surface, which helps to buffer against extreme cold
  • creating cold air drainage channels up-slope with a swather or hay mower
  • investigating the effect of crop nutrition - potassium, nitrogen and copper - on frost of water to the soil surface. Reducing the amount of water at the soil surface reduces the buffering ability, allowing the air temperature above the soil to fall to very low levels

Program 4 Contact: Mr Garren Knell 08 9881 5551 email

Region National, North, South, West