According to research supported by growers and the Federal Government, through the Grains Research and Development Corporation (GRDC), false breaks occur in almost two of every three WA seasons.

False breaks happen when enough rain falls to tempt seeds to germinate, followed by a dry period which kills the seedlings. Such weather betrayal kills many pasture legume species.

Senthold Asseng and Ross Chapman of the CSIRO reviewed the frequency and impact of false breaks on subterranean clovers in WA’s south-west and found that they stripped pastures of the species’ valuable legume feed herbage and nitrogen fixation capacity.

Examining more than 80 years of weather records from 10 WA locations between Mullewa and Esperance, Drs Asseng and Chapman looked for the most common time of year when false breaks occurred.

They found that a February false break was unlikely because it required rain to fall in quantities large enough to avoid immediate evaporation and to cool the soil sufficiently to overcome seed embryo dormancy. Rainfall events of such magnitude were uncommon in February.

At the other end of the spectrum, false breaks were scarce in May, which was generally too deep into the season for a persistent dry period to follow opening showers.

The riskiest 14-day period for false breaks fell between the 85^th and 98^th days of the year (late March to early April), with the risk remaining high in neighbouring weeks.

Unfortunately, the inbuilt false break guard of subterranean clovers has often faltered by this danger-time, with WA’s extreme temperatures baking and chilling the seed’s hard shells into submission by February and exposing the kernel to teasing rains.

This means subterranean clovers are not well adapted to resist false breaks, perhaps explaining the species’ poor persistence in local pasture systems.