Australia
November 30, 2015

• Yield holds the key to maximising sorghum profitability
• Optimising grain sorghum production in the low - medium and medium - high rainfall zone requires a greater emphasis on matching agronomic management to the environment rather than just on hybrid selection
• GRDC supported research is evaluating the role that hybrid, sowing time, nutrition, row spacing and plant population plays in optimising sorghum yield potential

Improving sorghum productivity in the northern New South Wales and western Queensland cropping belt will hinge on growers’ abilities to better match agronomic management to growing conditions.

That’s one of the key findings from a four - year research project funded by the Grains Research and Development Corporation (GRDC) into sorghum agronomy and the role that hybrid, sowing time, nutrition, row spacing and plant population plays in optimising yield potential.

The research, conducted in collaboration with NSW Department of Primary Industries (NSW DPI), aims to boost grower confidence in the reliability and potential profitability of sorghum as a cropping option and raise the yield bar in areas where sorghum is already an important rotational crop.

Leader Northern Dryland Cropping Systems with NSW DPI, Loretta Serafin (pictured) said research data confirmed that sorghum profitability was yield-dependant and that careful agronomic management was the key driver in maximising yield potential.

“The figures tell a clear story - if you want to make more money from sorghum, you need to improve yield,” Ms Serafin said.

“In order to optimise grain sorghum production in both the low - medium and medium - high rainfall zone there needs to be a greater emphasis on matching agronomic management to the environment rather than just on hybrid selection.

“Certainly hybrids have a role to play based on their suitability for the environmental conditions and the relevant plasticity of their characteristics such as tillering, however in the trials conducted to date, the genetic potential of the hybrid has rarely been the limiting factor.

“The major agronomic drivers of yield seen to date have been crop nutrition, in particular nitrogen and phosphorus in combination, row configuration in the western (NSW) zone and achieving optimum planting densities.”

The research has been conducted across two projects - sorghum production west of the Newell Highway in northern NSW targeting the matching of suitable hybrids to optimum plant populations and row configurations; and high yielding sorghum agronomy in the eastern zone, on the Liverpool Plains.

The Western Zone Project encompassed a series of nine dryland trials over four years between 2010 and 2014 and evaluated three primary factors - row configuration, plant population and hybrid selection although additional data was gathered on issues such as crown rot, soil water and nitrogen.

The results suggest that early plant sorghum is currently a more attractive proposition for growers than late plant sorghum, mostly due to logistical and rotational reasons. However Ms Serafin said the results needed to be considered in context given that the three late plant trials were all undertaken in the 2012/13 growing season.

“Currently the case for or against early or late sowing time is largely based on the impacts on the farming system as there is insufficient data to build a more robust case on the impact on crop yield,” Ms Serafin said.

“Early plant sorghum, sown in September/October is intended to escape the summer heat at flowering as well as splitting the labour and equipment requirements more evenly across the year so winter crop planting and summer crop harvest do not coincide.

“Early planted sorghum is also typically harvested while conditions are still warm meaning a quick dry down time, no grain drying and harvest before the pressures of winter planting.

“The early harvest timing also allows the option of a double crop back into chickpeas or a winter cereal should sufficient rainfall occur to re-fill the soil profile sufficiently, speeding up the move back into the more dominant winter cropping sequence.”

The western trial work also found that yield declined as effective row spacing increased. The solid plant configuration produced the highest yields, on average 4.19 t/ha, compared to 3.47 and 3.48 t/ha for single skip and super wide respectively and 2.73 t/ha for double skip.

The one trial site with a 2.0 m solid plant treatment averaged 3.13 t/ha. This equates to the solid plant yielding 17% more than the single skip or super wide and 34% more than the double skip.

“That said, the average yield of these sites was 3.46 t/ha which is more than a 1 t/ha higher than the long term average for grain sorghum in the north west,” Ms Serafin said.

“So we need to be mindful of the high risk of planting solid in these western environments as well. Indeed using a single skip or superwide configuration is a good compromise, limiting your risk of total crop failure in a dry year but still capturing some of the top end yield potential in the better seasons.”

Additional recommendations from the western zone trial work include targeting plant populations in the realm of 30 – 50,000 plants/ha and selecting hybrids which have a moderate to high level of tillering as this mechanism allows plants to respond to variable environmental conditions.

The second sorghum agronomy project - the High Yielding Cereals Project - began in the 2014-15 season and targets the medium - high rainfall zone where sorghum is reliably grown but crop modelling suggests there is disparity between potential crop yield and the actual yield harvested by growers.

This trial work is attempting to partition the impact on grain yield of altering various agronomic factors such as hybrid, plant population, row configuration and nutrition.

Three trials were conducted in the 2013/14 season at two sites - dryland trials at Pine Ridge and dryland and irrigated sites at Breeza.

Each trial included the following treatments: two times of sowing - ideal and late plant; two row configurations - 90cm solid (2 rows per plot) and a twin row (4 rows with pairs of 2 rows 7.5cm apart); three hybrids - MR Buster (as a current commercial benchmark) and two recently released hybrids MR Scorpio and 85G33; three plant populations - 50, 75 and 100,000 plants/ha; three nitrogen application rates - 0, 100 and 200 kg/ha applied as Urea at sowing; and three phosphorus application rates - 0, 10 and 20 kg/ha applied as Triple Superphosphate at sowing.

“The aim of the trials was to allocate proportions of the final crop yield to various agronomic decision points, for example if no nitrogen was applied to a sorghum crop but all other management decisions were optimised, how much yield would a grower lose?” Ms Serafin said.

“Preliminary results from the High Yielding Cereals project suggest that growers and agronomists should address nutritional issues as a priority for sorghum compared to the relatively minor responses to hybrid and population to ensure that crops are meeting their water limited yield potential.”

Similar to the trial work undertaken in the western zone, the early plant sorghum out yielded the late planted sorghum under both the dryland and irrigated trials in the High Yielding Cereals project.

The performance difference between hybrids was small, however Ms Serafin said the difference between varying agronomic factors was much larger, in particular the varying of nitrogen rate.

She said optimum plant populations were between 50-75,000 plants/ha in both the irrigated and dryland trials and there was minimal difference in the yields of 90cm row spacing compared to the twin row configuration.

Further detail on the trials is available by downloading a copy of Ms Serafin’s Update paper from the GRDC website http://www.grdc.com.au/Research-and-Development/GRDC-Update-Papers/2015/02/Sorghum-agronomy-to-maximise-yield-potential.

Website: http://www.grdc.com.au

Published: November 30, 2015