A 2015 time-of-sowing trial conducted at Gulargambone in western NSW resulted in average yield from a April 28 sowing 38 percent higher than a May 16 sowing.
Suntop, a mid-season variety for example yielded 6.0 t/ha from the earlier sowing. But while still in the leading yield group just topped 4t/ha from a May 16 sowing.
Agricultural Marketing and Production Systems (AMPS) research agronomist Matt Gardner, who leads a time-of-sowing study across the northern slopes and western plains, notes that earlier sowing has generally out yielded later sowings.
However he stresses it is important to minimise frost risk from earlier sowing with appropriate safeguards such as careful choice of variety.
Other research groups have noted similar results generally favouring earlier sowing than is generally considered standard practise.
For example a Department of Primary Industries research team led by Rick Graham at the Narrabri University of Sydney Research Centre recorded main season varieties Gregory, Lancer, and Suntop yielded best when sown at the start of their recommended sowing windows.
Matt Gardner and Rick Graham stress the importance of choosing varieties carefully for earlier sowings.
For example a fast-maturing variety sown earlier than recommended (for that variety) is likely to commonly be badly frost damaged.
In the 2014 Narrabri research early sowing of short season varieties resulted in yield penalties of 42 per cent. Dart yielded 2.4t/ha from an early sowing (April 23) compared with 5.6t/ha from a May 15 sowing, mainly because of frost damage.
Durum wheat Hyperno suffered a 67pc yield reduction from early sowing (1.48t/ha versus 4.43t/ha).
Warmer winters in recent years (climate change or climate variability) generally means all varieties except those with winter habit (especially for north west areas) tend to develop faster from all sowing times.
This would seem to create extra frost risk if sowing too early, as late winter spring frosts do not appear to be receding.
Research supports earlier sowing of a given variety in the earlier part of its sowing window. And often switching to a slower maturing variety for early sowing is higher yielding than quicker maturing varieties sown in the earlier part of their window.
Each season has its particular risks and issues related to sowing time.
Early sowing has commonly been an advantage for many crops in the current season’s wet winter early spring. Early sowing allowed crops to establish and commonly better cope with following semi water-logged conditions than later sown crops. Plus late sowing commonly gets further delayed because sowing conditions are too wet.
Five of the past seven years for many areas has experienced dryer than average springs, sometimes combined with hotter than average conditions. As long as earlier-sown crops escape a major frost earlier grain fill has been way ahead of later crops.
Even frost damage can erratically affect crops. I have commonly seen in my crop trials days with NSW DPI that a frost would affect directly the opposite to what one would normally expect. A frost might devastate a later heading crop because it was at the most vulnerable stage, but a quicker maturing earlier heading variety may have passed that highest risk stage and suffered little damage.
Earlier sowing comes with added risks.
Diseases such as leaf and virus diseases can be higher risk, as well as some root rots.
Early sowing provides less opportunity to control weeds prior to sowing but early sowing can result in better crop weed suppression.
Next week. Shock of finding poisonous weeds on new properties.
- Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or contact (0428) 752 149.
