Benefits, risks of sowing pulses early
From the March 2009 edition of Agriculture Today.
Earlier sowing has been the saviour of many growers in the hot, dry springs that have dramatically affected pulse crop yields for the last four seasons across southern and central NSW.
Earlier sowing has enabled crops to set and fill grain before the onset of above average temperatures and to more effectively use limited spring rain.
Growers are now asking if they should bring sowing times forward to adjust to hot drier seasons.
Current sowing window recommendations for field pea, chickpea and faba bean varieties in NSW are updated as new research, farming systems and varieties come along.
Current research by NSW Department of Primary Industries (DPI) as part of a Grains Research and Development Corporation (GRDC) project has confirmed the benefits of early sowing chickpea and faba bean during dry seasons such as 2007 and 2008.
This effectively brought forward flowering and pod fill of the crop to more ideal temperature and moisture conditions.
Yield losses of around 10 to 30 kilograms per hectare per day were recorded in these experiments when sowing was delayed beyond mid May.
Delayed sowings also severely reduced plant height and increased harvest difficulties and seed losses.
These experiments were supported by separate detailed phenology studies giving a clearer picture of how extremes of temperature (frost and heat stress) impact on pod set in chickpea, faba bean and field pea across a range of flowering times.
Whilst sowing early will obviously have benefits in dry seasons, it could have potential pitfalls in other seasons.
Most importantly, climate models and forecasts are still too unreliable to accurately discern between wet or dry autumns or springs.
Sowing early under the expectation of a dry season may have huge management implications for disease, frost, harvest and weeds if the spring turns wet.
Disease could be the biggest problem with early sowing in average to wet seasons.
It is well known that disease pressure and intensity is favoured by early sowing, particularly for blackspot in field peas, chocolate spot in faba bean, Ascochyta and botrytis grey mould in chickpea and bacterial blight in field pea.
The main management options here are to maintain sound rotations and farming practices, use varieties with the best known disease resistance and use disease free seed.
Frost damage can be severe on pulse flowers and pods, and ideally they should flower only after the frost period has finished.
Early sowing has the inherent danger of pushing flowering into this period, and under these conditions, the only options are to avoid high risk areas such as low lying paddocks, sow a range of varieties and maturities to spread the risk and to allow as much sunlight to reach the ground to warm the soil by keeping stubble standing and widening the rows.
Early sowing under average to wet seasons can also encourage excessive growth and bulky crops.
This in turn leads to lodging, shading, pod abortion, lower yields, harvest difficulties and increased harvest losses.
The best management options here would be to choose shorter, more erect varieties and harvest aids such as desiccation.
Early sowing limits opportunities for weed control by restricting the pre sowing time period for knockdown.
In these circumstances, choose paddocks with low weed burdens.
Growers should seek further advice from their local agronomists.
Contact Luke Gaynor or Eric Armstrong, Wagga Wagga, (02) 6938 1999 or Peter Matthews, Temora, (02) 6977 3333.
Sowing early buffers crown rot
Growers should not be discouraged from sowing cereals earlier in the planting window for a variety for fear that they may increase crown rot losses.
Decisions on planting date should first be made to take advantage of earliest adequate soil moisture conditions to maximise yield and quality, according to NSW Department of Primary Industries plant pathologist at Tamworth, Steven Simpfendorfer.
"Variety maturity can then be used to manage frost risk," Dr Simpfendorfer said.
A trial he conducted at Tamworth has highlighted the impact of sowing time on crown rot.
The work was done with three wheat varieties, EGA Gregory, Strzelecki and EGA Wylie, sown either infected or uninfected with the crown rot fungus on three sowing dates,May 21, June 10 and June 27.
"Sowing date had the largest impact on final yield followed by variety choice," Dr Simpfendorfer said.
"The effect on yield of those two factors far outweighed the effect of crown rot."
"Delaying sowing for 37 days between the first and last sowing dates reduced yield by one tonne per hectare, with crown rot causing a further 0.2 t/ha loss."
Delayed sowing had a similar effect on grain quality with a four per cent increase in screenings due to latter sowing and an additional 1.3pc increase in screenings when crown rot was considered.
Grain size as measured by 1000 grain weight was also impacted by delayed sowing with a 6.5 gram decrease due to later planting and an additional 1.3g reduction from crown rot infection.
Earlier sowing did not increase the levels of crown rot infection in any of the varieties, even though in theory they were exposed to infection for a greater length of time.
The 2008 season was very conducive to infection, with good soil moisture for much of the year.
But the longer season varieties, EGA Gregory and Strzelecki, did not show increased susceptibility to infection when sown earlier.
However, delaying sowing did increase the severity of crown rot as measured by the extent of basal browning in infected tillers.
Moisture stress during grain fill is known to worsen losses to crown rot.
The 2008 season was not overly conducive to yield and quality loss from crown rot, but differences were still measured.
Bringing grain-fill forward even one to two weeks with earlier planting may have a considerable impact on disease expression by limiting moisture and evaporative stress during grain fill.
Dr Simpfendorfer said the percentage yield and quality losses attributable to crown rot (which increases the probability of downgrading) were fairly consistent across the three sowing dates.
"If anything they got slightly worse with the later sowings," he said.
"Hence, sowing earlier in the window if soil moisture allows maximises the genetic yield potential, grain size and limits screenings in a variety.
"This provides buffering from any detrimental effect that crown rot infection may then have."
Contact Steven Simpfendorfer, Tamworth (02) 6763 1261, steven.simpfendorfer@dpi.nsw.gov.au
