Seedling survival in marginal moisture

The practice of dry sowing has become increasingly common with frequent years of below average rainfall in the sowing season. Dry sowing, where crops are sown into a dry seed bed before season breaking rainfall, has helped farmers decrease production risk and manage workload.

With persistent warm, dry conditions and no rain forecast on the horizon, concerns on how long germinated crops can survive on marginal moisture is at the forefront of grower minds. BCG conducted a study in 2008, where seedling survival was observed over 2.5 weeks before follow-up rain was received. The study determined germinated but not emerged crops survived at least 2.5 weeks before further rain was received.

Similarly to the research conducted in 2008, BCG is currently investigating seedling survival across the region. Initial assessments have been made at grower paddocks in Birchip, Curyo and Quambatook and will continue throughout the season, to determine how long the germinated seed can remain viable, how establishment was affected, and how safe it is to dry sow with no rain on the forecast.

Rainfall received during summer has provided moisture at depth, but crops were sown into dry topsoil. The ANZAC Day rainfall event varied across the region, with totals ranging from 0-5mm in some areas and over 60mm in others. This rainfall proved enough to germinate dry sown wheat and canola at Birchip and Curyo, and for canola to germinate and emerge at Quambatook.  Barley at Birchip, sown 4cm deep into moisture following the ANZAC day rain has not germinated yet.

Scepter wheat observed at Birchip, sown dry on 25 April to 1cm depth, has germinated with roots and shoot. Hybrid canola at Curyo, sown dry on 11 April to 2-3cm depth, showed some germination with roots developing.

BCG will continue monitoring seedling survival on marginal moisture over the coming weeks to determine how long germinated but unemerged seeds can survive and if establishment is affected.

If you are still weighing up your options, BCG is hosting a short informal Q&A forum online next Thursday 15 May at 12pm for farmers and advisors navigating canola establishment challenges. Whether you’re dealing with patchy emergence, unsure about plant population thresholds, or considering a resow, this is your chance to ask questions and hear directly from the researchers and agronomists. Go to https://bit.ly/canola-webinar to RSVP.

May 9: 

Germinated wheat and canola were observed beneath the soil surface at Birchip and Curyo, both with developing root systems. 

May 14: 

BCG expanded upon the assessment by implementing a simulated rainfall demonstration to Birchip wheat and Curyo canola. To test the viability of the germinated but not emerged seed, 5 and 10mm rainfall simulations were created by measuring out a square metre and watering with five and ten litres respectively.  

Quambatook canola had fully emerged with strong root development. 

 

May 19: 

Demonstration plot that received 10mm of simulated rain had some emergence. 

No emergence was observed on 5mm wheat or either 5mm or 10mm canola.  

May 21: 

One week following simulated rainfall, both the 5 and 10 millimeter wheat plots had emergence. One plant was counted in the five mm plot and nine plants were counted in the 10mm plot. 

The canola at Curyo had no emergence. Minimal scratching was done for seed to avoid disturbance. All plots were rewatered to determine the effects of follow up rain. 

A replication of the rainfall simulation was created at Birchip and Curyo to further test the viability of the seed.   

 

Canola at Quambatook at GS14.

May 28:

Curyo canola watered with 10mm twice had one plant emerged. There was no emergence across the 5mm plots watered on 14 May and 21 May, or the 10mm plot watered on 21 May.

Birchip wheat had emergence in all plots aside from the 5mm plot watered on May 21.

All plots have been rewatered to continue monitoring emergence and establishment.

June 6:

Curyo canola had 3 plants per square meter in the plot watered with 10mm three times. There was no emergence in the other plots.

Birchip wheat had no change, with emergence in all plots aside from the plot watered with 5mm twice.

Plots have not been rewatered this week. With rainfall forecast on 6 and 7 June, further observations will be made next week on establishment.