Crop sequencing for irrigated double cropping within the Murrumbidgee Valley region

Background

The project aims to qualify and overcome some of the potential difficulties with double cropping systems (growing a winter and summer crop following one another) and to provide the opportunity for growers to capitalise on their investment in irrigated agriculture. This project addressed the issues of herbicide residues, irrigation layouts and management, stubble management and quantifying achievable crop yield and profitability.

The project has two core sites with one located in Boort (Northern Victoria) and the other located at Leeton Field Station (LFS) in southern New South Wales (NSW). The Victorian site is focusing on the technical aspects of double cropping including herbicide options and stubble management and the NSW site focuses on cropping sequences. This report is on the results of the replicated experiment at LFS where the focus is on evaluating the different crop sequences to quantify achievable crop yield and profitability.

Methodology

The trial site was established at LFS in a field with a history of irrigated lucerne. The paddock was formed into 1.83m wide beds suitable for furrow irrigated cropping. The crop sequencing started in early 2014 with a winter cropping or fallow phase. The project will run for two years (four cropping seasons) ending in mid 2016 with the harvest of the second summer cropping phase.

The trial includes both single cropping (one crop per year) and double cropping (two or three crops in two years) treatments. The experiment has seven treatments with four replications of each treatment (Table 1). Each plot includes three beds 1.83m wide by 120m long, giving a total plot area of 660m² and a treatment area of 0.264ha. There is a fallow buffer area of one bed between each plot.

Table 1: Summary of the seven treatments evaluated in the LFS crop sequencing experiment.

	Treatment
Season/Year	1	2	3	4	5	6	7
Winter 2014	Fallow	Fallow	Fallow	Wheat	Wheat	Barley	Canola
Summer 2014-15	Soybean	Soybean	Cotton	Soybean	Fallow	Soybean	Maize
Winter 2015	Fallow	Fallow	Faba bean	Wheat	Wheat	Barley	Faba bean
Summer 2015-16	Maize	Soybean	Fallow	Soybean	Fallow	Soybean	Fallow

Table 2 shows the commodity prices used in the GM analysis. Most prices (ex-GST) were sourced from the Igrain website for the 2014-15 season. Current commercial (ex-GST) prices were sourced from retailers or contractors for the cost of chemicals, fertilisers and contract harvesting. Some cotton costs were sourced from the NSW DPI 2014-15 cotton GM budgets for Southern NSW. Commodity prices and variable input costs were kept consistent over both years to ensure the final results were not impacted by using inconsistent sources of input data across seasons.

Table 2: Summary of commodity prices used.

Commodity	Price
Wheat - APW	$258 per tonne
Barley	$241 per tonne
Canola - No grade	$449 per tonne
Soybean - No grade	$512 per tonne
Maize - Feed	$287 per tonne
Cotton lint	$500 per bale
Cotton seed	$300 per tonne
Faba beans	$450 per tonne

Results and discussion

Treatment One

The 2014 winter phase was left as fallow. The 2014-15 summer crop was sown with Djakal soybeans on 20 November 2014, irrigated with 8ML of water and harvested on 5 May 2015 with a yield of 3.09t/ha. The 2015 winter phase was left as fallow. The 2015-16 summer phase was sown with P1756 maize on 7 October 2015, irrigated with 10ML of water and harvested 22 March 2016 with a yield of 13.4t/ha.

Treatment Two

The 2014 winter phase was left as fallow. The 2014-15 summer crop was sown with Djakal soybeans on 20 November 2014, irrigated with 8ML of water and harvested on 5 May 2015 with a yield of 3.36t/ha. The 2015 winter phase was left as fallow. The 2015-16 summer phase was sown with Djakal soybeans on 26 November 2015, irrigated with 7ML of water and harvested 6 April 2016 with a yield of 3.09t/ha.

Treatment Three

The 2014 winter phase was left as fallow. The 2014-15 summer crop was sown with Sitcot 71 cotton on 1 October 2014, irrigated with 10ML of water and harvested on 29 April 2015 with a yield of 13.95 bales/ha. The plots were then cultivated and prepared for the 2015 winter phase with faba beans sown on 22 May 2015. The faba beans were irrigated with 3.1ML of water, harvested on 9 December 2015 with a yield of 4.52t/ha. The 2015-16 summer phase was left as fallow.

Treatment Four

The 2014 winter phase was sown to Dart wheat on the 23 May 2014, but due to poor establishment, the crop was re-sown on 20 June 2014. The wheat was irrigated with 3.5ML of water, harvested on 11 December and achieved a yield of 5.25t/ha. The wheat stubble was burnt and the 2014-15 summer phase of Djakal soybeans was direct seeded on the 16 December 2014. The soybeans were irrigated with 7ML of water and harvested on 21 April 2015 with a yield of 2.79t/ha. The plots were then cultivated and prepared for the 2015 winter phase with Corackwheat sown on 16 May 2015. The wheat was irrigated with 3.1ML of water and harvested on the 23 November 2015 with a yield of 6.64t/ha. The 2015-16 summer crop was sown with Djakal soybeans on the 26 November 2015, irrigated with 7ML of water and harvested 5 April 2016 with a yield of 2.69t/ha.

Treatment Five

The 2014 winter phase was sown to Dart wheat on 23 May 2014, but due to poor establishment, the wheat was re-sown on 20 June 2014. The wheat was irrigated with 3.5ML of water and harvested on 12 December with a yield of 5.17t/ha. The 2014/15 summer phase was left as fallow. The 2015 winter phase was sown to Suntop wheat on 16 May 2015, irrigated with 3.1ML of water and harvested on the 1 December with a yield of 7.01t/ha. The 2015/16 summer phase was left as fallow.

Treatment Six

The 2014 winter phase was sown to Scope barley on 23 May 2014, irrigated with 3.5ML of water and harvested on 29 November 2014 with a yield of 4.19t/ha. The barley stubble was burnt and the 2014-15 summer phase of Djakal soybeans was sown on 2 December 2014. The soybeans were irrigated with 7.5ML of water and harvested on 21 April 2015 with a yield of 2.79t/ha. The plots were then cultivated and prepared for the 2015 winter phase with Spartacus barley sown on 18 May 2015. The barley was irrigated with 3.1ML of water and harvested on the 18 November 2015 with a yield of 6.11t/ha. The 2015-16 summer phase was sown with Djakal soybeans on 26 November 2015, irrigated with 7ML of water and harvested 5 April 2016 with a yield of 2.86t/ha.

Treatment Seven

The 2014 winter phase was sown to Hyola® 50 canola on 16 May 2014, irrigated with 3ML of water and harvested on 13 November 2014 with a yield of 3.44t/ha. The 2014-15 summer crop of Pioneer® P0012 maize was direct seeded on 21 November 2014. The maize was irrigated with 9ML of water and harvested on 21 April 2015 with a yield of 9.75t/ha. The plots were then cultivated and prepared for the 2015 winter phase with faba beans sown on the 22 May 2015. The faba beans were irrigated with 3.1ML of water and harvested on 9 December 2015 with a yield of 4.57t/ha. The 2015-16 summer phase was left as fallow.

Table 3: Gross margin return per hectare ($/ha) for each crop in the LFS crop sequencing experiment.

	Treatment
Season/Year	1	2	3	4	5	6	7
Winter 2014	Fallow	Fallow	Fallow	Wheat $540	Wheat $521	Barley $299	Canola $566
Summer 2014-15	Soybean $903	Soybean $1000	Cotton $4766	Soybean $863	Fallow	Soybean $962	Maize $1275
Winter 2015	Fallow	Fallow	Faba bean $1462	Wheat $790	Wheat $907	Barley $785	Faba bean $1515
Summer 2015-16	Maize $2111	Soybean $971	Fallow	Soybean $844	Fallow	Soybean $931	Fallow

Table 4: Gross margin return per Megalitre ($/ML) for each crop in the LFS crop sequencing experiment.

	Treatment
Season/Year	1	2	3	4	5	6	7
Winter 2014	Fallow	Fallow	Fallow	Wheat $154	Wheat $149	Barley $85	Canola $189
Summer 2014-15	Soybean $113	Soybean $125	Cotton $477	Soybean $123	Fallow	Soybean $128	Maize $142
Winter 2015	Fallow	Fallow	Faba bean $473	Wheat $255	Wheat $293	Barley $253	Faba bean $489
Summer 2015-16	Maize $211	Soybean $139	Fallow	Soybean $121	Fallow	Soybean $133	Fallow

In the first cropping phase (winter 2014), all treatments had a relatively low GM return for both $/ha and $/ML. The low returns were due to low yields for the cereal crops and a low commodity price for canola.

In the second cropping phase (summer 2014-15), the cotton treatment had the highest GM return for both $/ha and $/ML. The very high returns resulted from a high yield and a high commodity price. The GM return for the cotton treatment was over 300per cent higher than the GM return for the maize treatment which had the second highest returns for both $/ha and $/ML. The soybean treatments suffered some early flowering moisture stress which likely reduced yield potential.

In the third cropping phase (winter 2015), the two faba bean treatments had the highest GM returns for both $/ha and $/ML. The GM return for the faba bean treatments was over 60 per cent higher than the GM return for all the other cropping treatments in that cropping phase.

In the fourth cropping phase (summer 2015-16), the maize treatment had the highest GM return for both $/ha and $/ML. The maize GM for $/ha was over 100 per cent higher than all other treatments, while the maize GM for $/ML was over 50 per cent higher than all other treatments.

Figure 1: Gross margin over return over two years from the LFS crop sequencing experiment.

The fallow/cotton/faba bean/fallow sequence (T3) had the highest GM return for both $/ha and $/ML. The high GM return for T3 resulted mainly from a high cotton yield (13.95 bales/ha) in summer 2014-15 and the high commodity price. The T3 GM/ha results were at least 85 per cent higher than all other rotations and at least 110per cent higher per ML. T3 also included a faba bean crop in winter 2015 which had a high GM result, which was second only to another faba bean crop (T7) in that particular season. The T3 rotation also used less water than most other treatments except the wheat/fallow (T5) sequence, which is reflected in the very large GM per ML result.

The second highest GM return for both $/ha and $/ML was the canola/maize/faba bean/fallow sequence (T7). The T7 rotation included three crops back-to-back, concluding in a summer fallow. The highlight of this rotation was the faba bean crop in winter 2015 which had the highest GM of the crops in this sequence, as well as the highest GM of all the winter 2015 treatments. This was in part due to a very good yield from the faba bean crop (4.57t/ha). The previous T7 maize crop in summer 2014-15 also had a comparatively high GM for both $/ha and $/ML despite the relatively low yield. The T7 rotation resulted in increased income compared to some treatments partly due to the fact that it produced three crops, while some other rotations only had two crops. It is also noted that the water use in T7 was comparatively low at 15.10ML/ha in total.

Other rotation results that compared favourably on a hectare basis and that were not much lower than that of T7 were the sequences that produced four crops in the rotation period. These were the barley/soybean/barley/soybean (T6) rotation and the wheat/soybean/wheat/soybean (T4) rotation. The T4 and T6 rotations resulted in comparatively good cumulative GM results ranging from $3,037/ha to $2,977/ha. There was variation noted between the GM results for T4 and T6 in individual years.

The wheat/fallow/wheat/fallow (T5) rotation had the lowest GM return on a hectare basis with a return of only $1,428/ha over the two years. Even though T5 had the lowest GM for $/ha, it had a much better GM return on a Megalitre basis with $216/ML.

Conclusion

Use of this data is useful to compare GM/ha for land use and water use across years. Outside the cotton effect, there is useful information and trends within this data. The T5 effect is of interest, as whilst it had the lowest GM/ha for land use, it was one of the best for GM for water use. This implies that if water is limited, growers need to seriously consider increasing the percentage of winter crops within their rotation and using summer fallows as a break. In contrast, if water is plentiful and of low cost, a more summer crop dominant rotation could be more profitable.

Growers need to fully understand the influence of commodity price, water cost and input costs on their overall farm profitability. This study aimed to help develop a realistic foundation for a decision support tool to be developed to account for variances in the fore mentioned price variables.

References

Napier T, Johnston D, Gaynor L, Podmore C, Singh P and Fisher R, ‘Crop sequencing for irrigated double cropping’, Southern NSW research results 2015, pp. 204–206.

Rollin M, Sykes J and Scott F, ‘Economic assessment for Correct Crop Sequencing for Irrigated Double Cropping’ Final report for ICC 2016, yet to be published, pp. 1–9.

Lush D, ‘The value of break crops in rotations’, Farmer’s Newsletter, No. 190 Autumn 2014, Irrigation Research and Extension Committee, pp. 32–33.

Acknowledgements

This research is a collaborative project between the GRDC, Department of Primary Industries and the Irrigated Cropping Council. 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 author would like to thank them for their continued support.

The support of Alan Boulton and Paul Morris for field work and data collection is gratefully acknowledged. The support of Fiona Scott and Rajinder Pal Singh for economic analysis is also gratefully acknowledged.

Contact details

Tony Napier
NSW Department of Primary Industries
Yanco Agricultural Institute, Private Mail Bag, Yanco NSW 2703
02 6951 2796
tony.napier@dpi.nsw.gov.au