Irrigation discussion group

WHY THIS PROJECT WAS NEEDED

The Riverine Plains Irrigation Discussion Group was formed as part of a project led by the Irrigated Cropping Council (now the Irrigation Farmers Network) which aimed to link new and innovative research investments by the Grains Research and Development Corporation (GRDC) with local farmer-driven groups.

GRDC have invested in a suite of irrigation research projects across the southern irrigation zones, including projects looking to develop and validate soil amelioration and agronomic practices for irrigated grain crops as well as maximising the dollar return per megalitre of water. To tie these research projects more closely with farmer needs, farmer-driven irrigation discussion groups were established across the southern region to enable farmers to be more actively involved in the irrigated grains research process.

In short: The Riverine Plains Irrigation Discussion Group helped farmers engage with irrigation research and helped align research with farmer needs. It fostered learning, networking, and trial experimentation, ensuring the relevance of research outcomes to local farmers.

The Riverine Plains Irrigation Discussion Group has helped farmers learn from one-another, build new peer and industry networks, gain access to the latest research data and provided the opportunity to shape project trial work to ensure it is relevant and meeting local needs. The discussion group also provided an opportunity for farmers to experiment with new techniques, research methods and develop ideas through local focus paddock trials on a local property.

The irrigation discussion group met four times annually to discuss agronomy and soil trials in the region and the implications of the research results at a local level.

Project outcomes

Key messages from the focus farm trials undertaken as part of the project in 2021 were that:

In wet and cold conditions, grazing irrigated wheat and canola requires more intensive management, and a stock containment area would be helpful to remove stock from paddock if waterlogged conditions are predicted.
A more even grazing can be obtained by crash grazing a large mob of sheep on a small area, compared to a small mob of sheep on a large area.
Sow the variety suited to your environment early, with sufficient seeding rates to establish desired plant density in the vicinity of 150plants/m² wheat and 30 plants/m²
Remove stock prior to wheat GS31 (early stem elongation) and canola two weeks prior to stem elongation to preserve yield potential.
Monitor livestock growth rates and feed test grazing crops to identify any deficiencies or toxicities and provide additional roughage to compliment the grazing crop.

Key messages from the 2022 focus paddock trials were that:

In 2022, high rainfall (decile 10) significantly impacted on yield and disease of faba beans
Due to the season, faba beans were largely unprofitable, even though there is evidence they can be profitable in dry years.
Dry matter measurements indicated that the nitrogen fixed could save up to $413/ha the following year in nitrogen costs (based on January 2023 pricing).

Irrigated faba beans - 2022 season results

Background

A local GRDC and Field Applied Research (FAR) Australia research trial has shown that higher planting densities in irrigated faba beans are correlated to higher yields. Faba beans are not regularly grown in local irrigation systems, so in 2022, a demonstration was sown to test and discuss the results with the Riverine Plains Irrigation Discussion Group.

Aim

To demonstrate that higher seeding rates in irrigated beans provides higher yields and to compare the economics of irrigated beans to irrigated canola and wheat.

Method

The site was soil tested on the 17 May 2022 to provide background information for the site (Table 1). Treatments were decided in consultation with FAR Australia and the host farmer, to test two varieties and a range of plant populations (Table 2). Treatments were two seeder widths wide (24m) and 1000m long.

Yields were measured by the host farmer’s yield monitor.

A gross margin analysis was completed at the end of the season to compare the profitability of irrigated winter crops in the region. The analysis used actual grain prices, irrigated yields, irrigation water (Table 3) and the following input prices: MAP $1,300/t, Urea $1,500/t.

Irrigation type centre pivot

Table 1 Site description

Irrigation type	Centre Pivot
Rainfall (mm): Jan – March	258
Rainfall (mm): April – October	498
Sowing date	22 April 2022
Row spacing	165mm
Soil type	Clay loam
pH CaCl2 (0-10cm)	5.9
Soil Mineral N kg N/ha (0-30cm)	101.6
Soil Mineral N kg N/ha (30-60cm)	22.1
Total Mineral N kg N/ha (0-60cm)	123.7
Phosphorus (Colwell)	39
Potassium (Colwell)	240
Sulphur (KCl40)	10

Results

Dry matter samples were taken from three treatments at mid-pod fill on the 17 October 2022. At this stage, the plants were badly lodged, and chocolate spot disease was causing loss of green leaf. Visual inspection indicated that the conditions had greatly reduced the number of pods on the faba beans.

The highest yielding treatment was four, the Paddock Amberley site (26 plants/m²), which yielded 0.98t/ha. The second highest yielding treatment was one, Bendoc (25 plants/m²) and the lowest yielding treatment was two, Bendoc (29 plants/m²), as shown in Table 2.

Due to waterlogging and disease conditions, the case study paddock of faba beans yielded approximately 1t/ha, dramatically reducing the gross margin to a loss of $349/ ha. As these results were not representative of all faba bean crops in the region, farmers were interested in the economics of faba beans in a situation where they were less waterlogged. As such, and in consultation with farmers, the economic analysis was based on actual prices, yields achieved in the region on irrigated paddocks (no irrigation water was applied in 2022), as shown in Table 3. The yields achieved were about 25% below the target set at the beginning of the year, due to waterlogging. The analysis showed that faba beans were significantly less profitable in 2022 compared to canola, due to lower yields and poorer prices (Table 3).

Table 2 Treatments

Treatment	Seeding rate (kg/ha)*	Plant population (plants/m²)	Dry matter at mid-pod fill (t DM/ha)	Grain yield (t/ha)	Estimated nitrogen fixation kg N/ha**
Control: Bendoc 22 plants/m²	150	21	11.9	0.68	190.4
1: Bendoc 25 plants/m²	170	25	#	0.71	#
2: Bendoc 29 plants/m²	200	29	8.4	0.26	134.4
3: Amberley 25 plants/m²	235	40	10.8	0.64	172.8
4: Paddock Amberley	170	26	#	0.98	#

*Seeding rates were calculated based on Bendoc 300 grain weight 148g, Amberley 300 grain weight 215g. #These plots were not measured. **Based on 16 kg N/t of above-ground DM (Glover et al, 2013).

Table 3 Economic parameters

Crop type	Actual price $/T	Actual yield (in the region) (t/ha)	Irrigation water applied (mm/ha)	Gross margin ($/ha)
Wheat	$350	5.2	0	$800
Canola	$700	2.8	0	$976
Faba beans	$300	3.0	0	$458

Observations and comments

The purpose of the demonstration was to show that higher planting densities for irrigated faba beans produce higher yields. However, the demonstration was affected by excessive rainfall, waterlogging and disease, which meant that the crop could not reach its potential.

In the 2022 scenario of high disease pressure, the highest seeding rates had the most disease pressure, and were lower yielding. The narrow row spacing of the paddock also provided conditions that favoured the spread of disease, as the large crop and narrow row spacing did not allow much airflow through the canopy.

The Amberley variety did appear to perform better than Bendoc, which may be due to its higher disease resistance. However, Amberley is a long season variety compared to Bendoc and not really suited to the Riverine Plains region, particularly when the region experiences a hot, dry spring.

If yields of 5.5t/ha plus can be achieved in irrigated faba beans, the returns are similar to irrigated wheat, however lower than canola. Historically, high gross margins of irrigated faba beans have been demonstrated over several years in the irrigated cropping trials at Kerang (Pers.comm D Jones, 2022) however there is very low adoption by growers. The results of this demonstration have shown that disease can be devastating in faba beans for both yield and gross margin, which explains the reluctance of growers to adopt them in irrigated cropping systems. If the faba beans can fix 190 kg N/ha, this is equivalent to 413 kg urea per hectare. Based on urea prices as of January 2023 of $1,000/t this represents a financial benefit in the following years of $413/ha. If this benefit can be realised by the following crops, it may provide farmers with more incentive to grow beans.

A lower risk option of incorporating a nitrogen fixing legume is to sow a high-density legume pasture option. This option has more flexibility as it can be made into hay or grazed by livestock. The ability to terminate the pasture early, by making hay or brown manuring, also makes it an effective option to then double crop with maize in an irrigated cropping system.

Acknowledgements

Riverine Plains would like to thank the Trevethan family who hosted this trial and provided the economic analysis. Riverine Plains would also like to thank Seednet for supplying some of the Amberley seed for the trial.