With legumes becoming more popular, research is underway to ensure they keep their place in farming systems

Frontier Farming Systems agronomist Michael Moodie has been running trials in South Australia’s Murray Mallee region to make sure legumes do not become a weak link in the farming system.

“We know that bringing legume crops into Mallee farming has improved the productivity and profitability of the system as a whole,” Mr Moodie says.

“A decade ago, productivity was declining with intensive cereal rotations, but in the past five to 10 years, legumes have become an important part of these farming systems.”

Production and area planted to legumes is up 50 per cent over the past decade.

Not only are there good economic reasons to consider legumes, but their nitrogen-fixing properties can also augment soil health. In boosting the diversity of growers’ cropping systems, legumes also have wider benefits.

Economic project

Mr Moodie is working as part of a GRDC investment, ‘Development and extension to close the economic yield gap and maximise farming systems benefits from grain legume production in South Australia’ (also referred to as the SA Grain Legume Project).

Led by the South Australian Research and Development Institute (SARDI), the project aims to address and close the 40 per cent yield gap between the current achieved legume yields and known water-limited yield potential through supporting growers with best-practice grain legume agronomy.

Trials and on-farm demonstrations are being undertaken at ‘hub’ sites at Hart, Tooligie and Loxton and ‘spoke’ sites at Cummins, Maitland, Millicent, Riverton, Tarlee, Pinnaroo, Mount Hope, Kimba, Bute, Coomandook and Melrose.

One of Mr Moodie’s priorities is to examine the challenges that are limiting legume production and to develop solutions.

At the project’s Loxton hub site, Mr Moodie is investigating poor legume performance on sandy soils, which is a major constraint for growers in terms of both productivity and profitability.

Deep ripping and nutrient amendments

Mr Moodie’s trials have shown that deep ripping – loosening the top 500 millimetres of the soil profile without inverting the soil – has shown promise on sandy soils.

In 2022, trials at Loxton found that deep ripping resulted in an impressive yield boost of 1.2 tonnes per hectare for both lentils and chickpeas on sandy soil compared to the control.

These trials also investigated whether crop response to deep ripping was enhanced by nutrient amendments. Six nutrient treatments were applied to lentils (GIA Lightning) and chickpeas (Genesis^™ 090) on deep sandy soil and loam soil.

Lentils were responsive to the application of starter fertiliser with a yield gain relative to the nil treatment control of 15 kilograms per 1kg of monoammonium phosphate (MAP) fertiliser applied, but chickpeas did not respond to the fertiliser treatments.

A lentil trial at Loxton in September 2022. Photo: Sarah Day

Soil amelioration

One of the 2022 trials investigated how lentils performed after soil amelioration on non-wetting sands at Pinnaroo.

Treatments included deep ripping (to 400mm), rotary spading (to 250mm with the aim of staying above the hostile clay subsoil), lime application (at 3t/ha), and combinations of these. Seeding with conventional wide row tynes was compared with narrow row disc seeding. The site was sown to PBA HighlandXT lentils on 28 April during a wet autumn following a drier-than-average summer.

Despite the narrow disc system resulting in a 20 per cent reduction in crop establishment and spading reducing early crop vigour through physical damage from sandblasting and pre-emergent herbicide damage, the soil amelioration approaches yielded 0.5t/ha more than the control. The narrow row disc seeder helped to preserve existing stubble and maintain minimum ground cover levels on fragile sandy soils.

Pre-emergent herbicide safety

Herbicide safety has been another focus, with pre-emergent herbicides a challenge for growers especially in lentils and vetch on sandy soils.

Trials at Loxton tested Group 5 herbicides metribuzin (750 grams/kg), diuron (900g/‌kg) and terbuthylazine (875g/kg), and Group 14 herbicide fomesafen (240g/L) at low and high label rates. Herbicides were applied in accordance with the label directions as either incorporated by sowing (IBS) or post-sowing pre-emergent (PSPE), tested with vetch (Timok) and lentils (GIA Lightning) sown on 4 May 2022.

For lentils, there was no grain yield penalty for any of the herbicides when applied IBS at the lower rates in this season. However, PSPE application of diuron at the lower rate and all other herbicides at the higher rates resulted in a yield penalty of between 25 and 50 per cent. Sowing depth did not affect lentil grain yield in the 2022 trials. For vetch, dry matter yield penalties were highest (35 to 40 per cent) where metribuzin, diuron and terbuthylazine were applied PSPE at the higher rate.

Time of sowing and seeding rate

The project also examined commercial lentil varieties suitable for low-rainfall areas.

“There’s a real fit for lentils in the low-rainfall zone,” Mr Moodie says. “We examined seeding rates and sowing time with the aim of improving harvestability, which is an issue for low-rainfall farmers.”

Production was at the extreme end of expectation in 2022, with no harvestability issues despite high biomass. GIA Thunder was the leading variety with an average grain yield of 4.2t/ha, but the good rainfall of the 2022 season made it hard to draw any concrete conclusions about the effect of time of sowing or seeding rate. Mr Moodie conducted further trials in 2023, with results pending.

Blight-tolerant chickpeas

Another 2022 trial tested the performance of a new Chickpea Breeding Australia (CBA) line of chickpeas with improved resistance to Ascochyta blight, compared with commercial varieties CBA Captain and Genesis^™ 090.

Each variety was grown with no fungicide applied (nil control) and regular fungicide applications to prevent the development of Ascochyta blight (full control).

Following planting on 26 May, all treatments remained free of Ascochyta blight until the end of September, before 200mm of rain fell in October and November. The very wet conditions resulted in spore showers that predominantly infected the chickpea pods.

Ascochyta blight infection during pod fill reduced the grain yield of Genesis^™ 090 and CBA Captain in nil control plots (no fungicide) by approximately 30 per cent. In the CBA chickpea line with enhanced Ascochyta blight tolerance, there was no significant difference in the grain yield of the full control or nil control treatments despite infection during pod fill.

Biggest benefits

Upcoming trials will focus on deep ripping, chickpea disease management and cost of production, and herbicide-tolerant lentil varieties. Mr Moodie notes that grower interest continues to increase, with legumes constituting 30 to 50 per cent of many growers’ farming systems.

“People are still trying to settle on the best mix,” he says. “There’s been some shifting over the last 5 to 10 years – farmers are continually adjusting their proportions of vetch, lentil, chickpea and field pea depending on factors such as price outlooks and seasonal conditions.” While the crop mix shifts depending on how each year plays out, Mr Moodie says that growers who chop and change too much after a few bad years will miss out when the good years come.

“You have to take the downs with the ups – you can’t chase your tail,” he says. “Legumes are more variable than cereal crops, but despite the downside risk there are seasons that bring incredible margins.

“High-value crops like lentils can return more than $1000 per hectare – but you have to be in it to win it.” 

More information: Michael Moodie, michael@frontierfarming.com.au; PIRSA Media, pirsa.media@sa.gov.au

See also: GRDC update paper – An integrated approach to effectively manage pulse diseases a South Australian perspective.