Farmer confidence to dry sow a proportion of their program into weed free paddocks is increasing, particularly as the Wimmera Mallee experiences more late break’s. However questions arose again this season as to “How long would a germinated cereal grain remain viable without follow up rain”?, and “How safe is it to sow into marginal moisture with no forecast follow up rain in sight?”
This year, BCG has investigated three barley paddocks sown into different soils and moisture conditions, observed germination and seedling survival over a number of weeks and undertook emergence counts after follow up rain. The observations made have high-lighted that germination yet un-emerged cereal crops did survive at least 2.5 weeks with no follow up rain. Observations from these three paddocks are shown below.
Case Study 1
Barber’s dry sowed Barque barley on the 24 of April at 55kg/ha on 17.5cm row spacing into a paddock with no starting soil moisture.
First Assessment (6/5/08)
After sowing, the crop received 6mm of rain on the 27 April, 6mm on the 30 April and 2mm on 1 May, thus providing some moisture for the seedbed to initialise germination. Therefore, on the 6 May when monitored there were some seedlings beginning to poke through the soil surface while others had only just started to put out a shoot and were establishing their root system.
Second Assessment (13/5/08)
By the following week, the seedlings had continued to grow, although there are some that had not yet emerged.
Third Assessment (29/5/08)
Just over a month after the crop was sown, a third assessment was undertaken.
In between this assessment and the last assessment, the paddock received 21mm of rain on the 17-18 May. This good soaking rain, in addition to sunny conditions since had encouraged all the seedlings to emerge and grow uniformly across the paddock. Many seedlings are already at the two leaf stage with a healthy root system. Germination counts were conducted at this assessment and were calculated to be 156 plants/m2.
Both emerged and unemerged seedling survival was at least 2.5 weeks after germination before follow up rain was received. It is thought that seedlings have the capacity to survive longer than the 2.5 weeks had follow up rain not been received.
Case Study 2
Warne’s first paddock was located near Berriwillock and was sown with Gairdner barley at a rate of 45kg/ha on the 26 April. The paddock received 25mm of rain at Easter (23 March) so was still reasonably moist at sowing. The paddock received 5.5mm the day after sowing and 4.5mm on the 30 April.
First Assessment (6/5/08)
The first visit was conducted on the 6 May, nearly two weeks after sowing. The rain after sowing had caused the plants to be in the early stages of germination. As you can see from picture 5, there root system is quite healthy.
Second Assessment (13/5/08)
A week later, the plants have continued to establish themselves, with some shoots pushing through the topsoil.
Third Assessment (29/5/08)
Just over a month later, we assessed this paddock again and conducted germination counts which revealed 78 plants/m2. The paddock had received 18mm on the 17-18 May and the seedlings have all emerged from the soil, looking green and healthy with a good root system.
Case Study 3
Warne’s second paddock to be investigated was located near Culgoa and was sown to Gairdner barley at a rate of 45kg/ha on the 24 April into a paddock with no stored moisture. 10mm of rain was recorded post sowing in two separate rain events before the first assessment.
First Assessment (6/5/08)
The first assessment was conducted on the 6 May nearly two weeks after sowing. Due to the heavy nature of the soil and lack of moisture at sowing, only a few seeds had shot and produced their roots.
Second Assessment (13/5/08)
A week later, the crop was surviving with some seeds starting to put their shoots out, but the majority were struggling and possessing a very fragile root system.
Third Assessment (29/5/08)
On the 17-18 May, 18mm of rain fell, assisting the germinated seedlings to continue to grow and establish themselves. Their overall appearance has improved but they require another significant rainfall event to look as healthy. Germination counts were conducted and recorded 74 plants/m2. Despite seedlings looking like they were under stress they still demonstrated that they could survive in a germinated but un-emerged state for at least two and a half weeks without follow up rain and still be viable to respond to the rain that did fall.
Future Work
BCG will continue to monitor these seedlings to assess how they are progressing. They will also be compared against some later sown crops to determine the differences in growth and survival. However, this experiment has shown that crops will emerge from marginal rain events and don’t seem to go mouldy in the soil.
