Risk awaits in planting date

Wheat head showing severe frost damage.
Wheat head showing severe frost damage.

YES, I'm writing about frost and what it can do to winter crops at this delicate stage - plus sincerely hoping for a couple of inches of rain on wheat, barley and chickpea paddocks.

Some Ascochyta blight has been found in our chickpeas this year but, until now, subsoil moisture has been a great springboard for chickpea yields without major disease issues.

Depending on where you are and your topography, frost or just conditions of below 10degC have put a dampener on chickpea yields with flowers aborted and seeds inside the pods turning black; a legacy of the frost in mid-late August.

All is not lost, as this cold snap occurred early in the flowering and podding time and, in general, there is sufficient soil moisture left to regenerate more flowers and, therefore, pods.

Yes, insecticide applications may have to be scheduled later for spraying helicoverpa but there are not too many of these eating machines on our chickpeas at the moment and we have effective products like indoxacarb, thiodicarb and our favourite biological insecticide in nucleo polyhedro virus - called Vivus Max.

CHICKPEAS is where I have the most concern for yield reductions but, conversely, this winter legume has the greatest capacity to regenerate with significant rain occurring as soon as possible this month.

I realise frosts are fairly infrequent from now on but it happened in the past and these past couple of years we've seen the extremes of weather. We had snapping frosts around September 10-11, 2011 and, while their impact was fairly negligible, I wouldn't like this to occur this month.

I have this theory when you have over 300 full pods per square metre - which numerically is fairly easy to achieve - then yields of 1.5 tonnes per ha are possible. So, in your inspections, if you find half a dozen pods per metre eaten out or frosted, then in the scheme of things it may not be a large percentage of your crop. Sure, I would rather it didn't happen but that's the risk you take with chickpeas, in that a planting date is your only control over frost damage and yield decrease.

WE all realise barley is fairly tolerant of frosty conditions and figures suggest a minus 3-4degC head-height temperature before losing significant numbers of seeds. Mind you, in 1997 there were plenty of acres of barley made into hay due to severe frosting.

Wheat, on the other hand, is more easily damaged by frost, due to its plant structure and development. Tipping is common, where the top seed levels are white and not grain-filled. Take care, as this visible condition can be confused with dry weather, crown rot and severe nutrient deficiency.

Many of you realise the early planting can give the biggest yield in winter crops. However, as always, it is a trade-off with the risk of frost. There is no control over frost in your winter crops, except planting date and topography, so when considering planting next year's crop, think back to previous years.

Former manager of Landmark Emerald, Paul McIntosh is now based on the Darling Downs.

Topics:  chickpeas columns commodities landmark paul mcintosh wheat

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