Identification of superior wheat varieties for sodic, magnesic and dispersive soils in the Albany port zone

Key messages

• The varieties Scepter, Hydra and Zen were outstanding yielders on this sodic site, although average yields were not significantly greater than Mace. Zen shows promise as it has been one of the top yielders over the two years of the trial so far on this sodic site in the medium rainfall region at Broomehill.
• The difference in performance of the highest yielders compared to Mace was greater in 2016 than the year prior. The average yield at this sodic site in the medium rainfall region was greater in 2016 (3.48t/ha) compared to 2015 (2.35t/ha).

Aims

To screen commercial and international wheat varieties to characterise and improve wheat variety productivity on alkaline sodic soil in the medium rainfall zone of Western Australia.

Background

Sodic soils are common throughout Western Australia, particularly in the south-west agricultural area where they occur mainly as duplex or gradational profiles and are a major soil constraint to wheat production. Sodic soils have multiple constraints including high pH, boron toxicity, salinity and high soil strength. These soils are structurally dispersive and have low porosity with dense (massive) structure and high soil strength when dry. Movement of air into these subsoils is poor, resulting in low oxygen availability to growing plants. Poor root growth on these soils limits the ability of plants to use subsoil moisture in the spring.

Because of these multiple constraints, research focus has moved from a single trait selection to the development of wheat germplasm with tolerance to multiple constraints. Little is currently known about the difference in sodicity tolerance of Australian wheat varieties in different rainfall zones. As part of a national project, this research in Western Australia has had trials in low (Kwinana East port zone) and medium rainfall zones (Albany port Zone) for two years. However, in this paper grain yield data from only medium rainfall (Broomhill) trials has been presented.  

Method

The site had one trial in 2015 and two trials in 2016. The 2016 trials were located next to each other (on the same soil type). One of the trials (named panel trial) had wheat varieties of Australian origin and a selection of lines with salinity exclusion genes while the other (named as International germplasm trial) included international wheat lines from countries mostly in Asia and the Middle East. These lines are part of a salinity nursery compiled on the basis of environments where they evolved. We hope that some of these international germplasm lines will have novel sources of tolerance and will be useful parents for future breeding work in Western Australia.

Broomehill is located 30 km south east of Katanning and is characterised by highly sodic, non-saline, alkaline grey clay with no magnesium issue and is partially affected by waterlogging during wetter periods in low lying areas of the site. Dispersion, electrical conductivity of a saturated soil extract (ECe) and pH typically increase with depth (Table 1).

Table 1. Soil characteristics of the trial site at Broomehill

By definition sodic soils have an exchangeable sodium percentage >6 and very sodic soils have an exchangeable sodium percentage (ESP) >15, but local experience in WA suggests that some soils start showing symptoms as the ESP increases above 2 (MyPaddock).

A non-sodic panel trial was also established at the Katanning Research Station but unfortunately due to frost this site was not harvested.

For the panel trial fifty seven wheat varieties were seeded in latinised randomised block designs at Broomehill (12 banks x 20 plots). Each variety was replicated four times and Mace was used as a repeated standard check.

The international germplasm trial had thirty six international lines including Mace seeded in a latinised randomised block with 4 blocks.

Seeding occurred on the 2^nd of June 2016 into good soil moisture and was harvested on the 19^th of December 2016. A range of measurements were taken throughout the growing season to track variety performance. A range of soil measurements such as an electromagnetic survey (EM38), and pH and electrical conductivity (EC) readings were also taken to characterize the soil and to account for variation across the site.

Results

Growing season (April to October) rainfall in 2016 was 243.5mm compared to 225.5mm in 2015 (Broomehill East weather station). Average daily pan evaporation from March to May was 3.1mm. September and October rainfall was higher compared to 2015 (28.9mm and 22.4mm respectively in 2016 compared to 18.3mm and 10.5mm in 2015). Senescence was delayed and crop maturity occurred around a week later compared to a ‘typical’ year.

None of the varieties in the international trial performed equal to or better than Mace. However they can still be ranked satisfactorily and will be useful in further testing and involvement in crossing work. The results presented in this paper focus on the panel trial which had primarily wheat varieties and germplasm developed in Australia. Results from the international trial are not included.

Initially the southern end of the panel trial was affected by waterlogging due to lower topography. This impacted plant establishment and growth, and yield was significantly lower. Because of this the results from the waterlogged area were excluded from the statistical analysis.

Whilst this trial had a total of 57 varieties, those presented in the Figures I and 2 were chosen as they are commonly grown by farmers in Western Australia or which have shown particularly interesting results.

Yield data are presented as the deviation from Mace (arguably the district standard variety). In these figures, vertical dashed lines refer to Mace and each variety is shown as an average point with two whiskers. The average point refers to mean difference from Mace (vertical dashed line) while the whiskers refer to the 95% confidence level.

The average yield across the trial was 3.48t/ha (+/- 0.17) which was greater than the average yield in 2015 (2.35t/ha +/- 0.19) but lower than the calculated seasonal yield potential of 3.9t/ha. This potential yield was calculated using an estimate of the crop available water at Broomehill East and an efficiency of 20kg grain/ha/mm of available water. Available water was calculated using a rule of thumb as equal to sum of a fifth of the summer rainfall (January to March) and two thirds of the growing season rainfall (Sharma and Anderson 2014).

Figure 1a

Figure 1b

Figure 1. Yield difference (t/ha) of Australian wheat varieties from Mace at Broomehill (sodic panel trial) in 2016 (a) and 2015 (b). The vertical dotted line represents Mace. The central point of the line for each variety is the mean deviation in t/ha from Mace and the whiskers represent +/- 2 times the standard error. The values were calculated following a Best Linear Unbiased Prediction (BLUPs) model.

Conclusion   

Results from 2016 have given further information about varieties that perform well on sodic soils in the medium rainfall region of Western Australia. Zen showed promise especially as it has been one of the top performers for two years so far. Additional analyses of crop growth and yield components will give us a comprehensive idea about manifestation of sensitivity and tolerance of the varieties to stresses associated with sodic soils in medium rainfall regions.

Continuation of this trial over a number of seasons and sites in the medium rainfall zone will further identify varieties that show tolerance to sodic, magnesic and dispersive soils. Multi-season and multi-site analysis of varietal performance and sensitivity is needed since the expression of constraints associated with sodic soils varies across seasons and regions. A multi-site analysis will be done with comparative trials from other sites within WA and other states.

References

Sharma DL, Anderson WK (2014) Success of diagnostic approach to rainfed, wheat-based cropping systems in Western Australia. Agricultural Systems 123, 22-33.

Acknowledgments

The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the authors would like to thank them for their continued support. Nathan Heron, farmer at Broomhill provided land and assistance for the trial at Katanning. Assistance at seeding and harvest from Meir Altman, DAFWA is gratefully acknowledged. DAFWA RSU staff from Merredin and Katanning aided in seeding, harvesting and agronomic management throughout the season.

GRDC Project Number: UA00159

Paper reviewed by: Dr. Raj Malik