Sorghum agronomy for profit in the western zone

Loretta Serafin, Guy McMullen, Matthew Gardner, Nicole Carrigan and Peter Formann
NSW Department of Primary Industries, Tamworth

Background

Dryland grain sorghum production in North West NSW is highly variable both in terms of area sown and tonnes produced. Typical farming systems are zero tillage and primarily winter based with cereal dominant rotations; this has led to major issues with crown rot (Fusarium pseudograminearum). Currently, the most reliable and profitable break crop is chickpeas however with increasing herbicide resistance and climate variability a reliable, profitable summer crop alternative is needed.

Sorghum producers in this area consider sorghum to be reasonably high risk, and in recent years have been disappointed in the lack of break crop benefits achieved when returning to wheat following sorghum.

Minimal dryland sorghum research has been conducted in this western zone (considered to be west of the Newell Highway) and has never focused on the interactions between crop management options, environmental conditions and hybrids. In the more favourable production areas in NE Australia research has shown that systems using skip configurations can reduce the risk of crop failure but often results in reduced yields (Whish et al. 2005). Commercially the adoption of double skip row sorghum has assisted in improving the reliability of sorghum in this zone. Under skip row configurations soil water in the unplanted area is conserved until later in the growing seasonal when the crop is able to access these resources to fill grain (Abunyewa et al. 2010). There has been little research to validate this as this practice or appropriate plant populations and the impact of hybrids with differing traits such as tillering and stay-green on crop performance in the low rainfall regions. In two high yielding seasons, the impact of varying these three key factors, row configuration, plant population and hybrid type were evaluated.

Research trials

Seven trials (table 1) were conducted over three summer seasons, 2010-11, 2011-12 and 2012-13. In the 2010-2012 seasons the trials were sown on the early planting window, whilst in the 2012-13 season all trials were planted in early January.

Table 1. Trial locations 2010-2013

Trials were sown with a four row Monosem single disc precision planter using RTK guidance and harvested with a KEW plot header. All sites were sown into wheat stubble from a long fallow. Experiments were designed as complete factorials set up as split-plots with planting configuration as main plots with hybrid and populations combinations as subplots, each replicated three times.

Each site included four row configurations; solid plant (SP), single skip (SS), super-wide (SW) (1.5 m) and double skip (DS), all on 1 m base row spacing, with the exception of Garah in the 2012 season which had a super solid (2.0m) configuration. The solid plant included all rows sown 1 m apart, while the single skip had two rows planted and one row unplanted or “skipped” on 1 m row spacings, the super wide had all rows planted 1.5 m spacing’s and the double skip had two rows planted and two rows unplanted.

Three plant populations were targeted at each site, 30, 50 and 70,000 plants/ha across each of the row configurations in the 2010-2012 seasons. In the 2012-13 season, target plant populations were changed to include 15, 30 and 50,000 plants/ha.

Three different hybrid types were used with different stay green and tillering characteristics:

• Low tillering, high staygreen  - LT10 (2010-11) and PAC2436 (2011-12 and 2012-13)
• Moderate tillering, moderate staygreen  - MR43
• High tillering, low staygreen – MR Bazley

Results

The two seasons of 2010-11 and 2011-12 were unseasonably wet for the NW region and combined with cooler temperatures, resulted in above average yields. Consistent results were achieved from all sites for the factors of configuration, population and hybrid. However there were no significant interactions between these three factors. 

The 2012-13 season was very dry during the spring and early summer which prevented sowing of the trials until the late planting window opened in early January. Good sowing rain was received across much of the north west in late December which allowed planting. High temperatures during sowing and post sowing reduced crop establishment below the targeted plant populations. However in crop rainfall allowed reasonable yield performance.

Configuration- early plant trial results( 2010-2012)

Responses to configuration under high yield (>4 t/ha) were consistent in these four trials. The SP yielded the highest while the DS configuration was the lowest yielding. At all sites the SS configurations yielded less than the solid, but more than the double skip. The SW configuration results were more variable than the SS, but yield results were generally consistent with the SS yields.

Table 2.  Grain yield from varying row configuration (averaged across population and hybrid) in four early plant trials (2010-2012)

Plant Population- early plant trial results (2010-2012)

Responses to changing plant populations were not as clear as those from altering row configuration. At two sites, Mungindi and Rowena the 30,000 plants/ha treatment yielded significantly less than the 50 and 70,000 treatments. At the other two sites, the response although similar was not significant.

Table 3. Grain yield from varying plant population (averaged across configuration and hybrid) in four early plant trials (2010-2012)

Hybrid Performance – early plant trial results (2010-2012)

The performance of the three hybrid types was consistent across the four sites. The low tillering, high stay green line (LT10 or 2436) yielded consistently less than the other hybrids in these trials. In the 2010-11 season MR 43 (moderate tillering/ moderate stay green) and MR Bazley (high tillering, low stay green) achieved equal yields. In the 2011-12 season MR Bazley produced higher yields.

Table 4. Grain yield from three hybrids (averaged across configuration and population) from 2010-12

Configuration, Plant population and Hybrid Performance- late plant trials (2012-13)

At the time of publication, the late planted trials had only just been harvested and grain quality testing was underway, as such results are not available.

Conclusion

On an early plant, in high yielding seasons, where yield potential is greater than 4.0 t/ha SP configurations consistently produced the highest yields. SS and SW configurations produce similar yield results to each other, but consistently lower than the solid plant. DS configurations yielded considerably less than all other configurations under these conditions. The impact of configuration on grain yield in this study support the findings of Whish et al (2005) in higher yielding regions. Populations of 30,000 plants/ha produced lower yields under the high yielding seasons. Plant populations should target 50-70,000 established plants/ha. Commercially populations of 70,000 plants/ha are not recommended as no benefit compared to the 50,000 population was found and additional seed costs would be incurred. The low tillering, high stay green hybrids used in these experiments were unable to produce competitive yields in favourable seasons. Hybrids with moderate to high levels of tillering responded more favourably to the improved seasonal conditions experienced in these two years.

References

Abunyewa A, Ferguson R, Wortmann C, Lyon D, Mason S, Klein R (2010) Skip-row and plant population effects on sorghum grain yield. Agronomy Journal, 102-1, 296-302

Whish J, Butler G, Castor M, Cawthray S, Broad I, Carberry P, Hammer G, McLean G, Routley R, Yates S (2005) Modelling the effects of row configuration on sorghum yield, reliability in north-eastern Australia Australian Journal of Agricultural Research, 56, 11-23.

Acknowledgements

This project is funded by NSW DPI and GRDC with support from Pacific Seeds. Thanks to Ben Frazer, Peter Perfrement, Rod Bambach, Patrick Mortell, Sarah Kampe, Steve Simpfendorfer, Alan Bowring and Jan Hosking, NSW DPI for technical assistance.

Thanks to Scott Carrigan “Kelvin” Gurley, Charles Boyle “Amaroo” Mungindi, Philip Harris “Wandahree“ Rowena, Tom and Neil Greentree “Morialta” Mungindi, Max and David Onus “Forestvale” Gurley, Charles and Fiona Brett “Kirribilli” Bullarah and Justin Malone “Byra” Garah for hosting the trials. Thanks to agronomists Brad Coleman, Rob Holmes, Tim Poole and Gary Onus for their assistance with the trial sites.

Contact details

Loretta Serafin and Guy McMullen
NSW Department of Primary Industries
Ph: 02 67 63 1100
Fx: 02 67 63 1222
Email: Loretta.serafin@dpi.nsw.gov.au or guy.mcmullen@dpi.nsw.gov.au