The agronomics of pulses, implications of new varieties and herbicide tolerance

Take home messages

• New varieties – two new ‘IMI’ tolerant lentil varieties will offer growers improved grain yield and yield stability across a range of environments.
• Herbicide tolerance - the first lentil to combine the IMI and metribuzin (MET) tolerances, GIA Metro, has been released. Whilst it is lower yielding than other varieties, agronomic herbicide tolerance trials have shown its metribuzin tolerance will allow alternative weed control strategies, particularly on sandy soils where metribuzin and other Group 5 products can cause crop damage risk even when applied post sowing pre emergent.
• Disease management – newer fungicide products provided profitable improvements in disease control under extreme conditions in 2022, particularly when combined with higher levels of varietal resistance.
• Soil constraints – deep ripping in combination with soil amendments provided yield gains of up to 180% in non-traditional areas for pulse production. Combining the agronomic response with new varieties with improved tolerance to soil toxicities, acidity, salinity, herbicides will contribute to expand areas for pulse production and improve yield stability.

Seasonal comments

From a research perspective, 2022 was the most challenging season I have experienced since the start of my career in pulses in 2000. ‘It was the year that just kept giving…and keeps giving into 2023…’. Almost all trial sites experienced good opening rainfall events, which resulted in even establishment and vigorous early growth for all pulses. The months of June and July were generally slightly below average and slight drought stress symptoms were noted in faba beans at drier locations. Then it all changed, at most sites more than 300mm of rain fell throughout August to October, followed by another 100mm or more during November at some sites. This meant that:

• several trials were abandoned due to waterlogging, particularly lentils
• disease management was incredibly difficult due to the high pressure and inability to apply timely fungicides due to trafficability
• maturity and harvest were delayed by at least 2–4 weeks compared to a ‘normal’ season. For example, this will be the first time lentil harvesting commenced at our Wimmera trial site in January (it’s normally finished by Christmas).

Due to the late season finish and delayed harvest, this report highlights some of the new pulse varieties and agronomic research completed in 2022, with more detailed results and grain yield available in the presentation.

Agronomic research highlights

Novel herbicide traits, weed management and new herbicides

The new lentil varieties combining IMI tolerance with metribuzin (GIA Metro) or residual clopyralid (GIA Sire) will improve weed control options in lentil, particularly in tight rotations. Trials in 2021 demonstrated improved vetch control when these traits were used with suitable herbicide packages. In 2022, trials at Ultima (central Mallee), with a background of the weed fumitory, and Kalkee (Wimmera), with a background of medic, investigated various options for control. Below, we focus on the metribuzin trait with GIA Metro.

Metribuzin tolerance

Similar to previous research, at Ultima in 2022, GIA Metro showed good visual tolerance to all metribuzin treatments, while PBA Hallmark XT showed significant crop damage in all post-emergent treatments (Table 1 and 2). Similarly, there was no difference observed in biomass or grain yield of GIA Metro from the herbicide treatments shown below. In contrast, PBA Hallmark showed a significant reduction in biomass and grain yield with post-emergent metribuzin treatments compared with no post-emergent application (Table 2) demonstrating the tolerance of the new variety Metro. Yield loss in PBA Hallmark was less than in other seasons which was reflective of the seasonal conditions where very high rainfall recorded from August to November, along with mild temperatures, meant there was adequate time to partially recover from the initial crop damage. In seasons with lower rainfall and less time for recovery, grain yield losses for PBA Hallmark XT from post-emergent metribuzin application can be much higher and result in complete failure, hence post emergent application of metribuzin to non-tolerant varieties is not permitted. It is important to note that, the population of fumitory in this trial was not high enough to create substantial crop competition and enable any meaningful observations on efficacy of control by metribuzin.

In the trial at Kalkee, similar trends in crop damage were observed (data not shown), however at the time of writing, grain yield was yet to be analysed.

Table 1: Application details of selected herbicide treatments applied in a trial near Ultima (central Mallee, Vic) to assess varietal tolerance and control fumitory in 2022. Application dates indicated in brackets.

1. Intercept® is the product registered for use in lentils
2. Metribuzin is registered for use in metribuzin tolerant lentils under permit ‘PER92810'

Table 2: Herbicide damage scores (26 July), biomass recorded (15 Nov) and grain yield (20 Dec) of GIA Metro and PBA Hallmark XT in response to selected herbicide treatments applied at Ultima (central Mallee, Vic) in 2022. Post-emergent treatments of metribuzin are highlighted.

*Denotes off label treatment – significant yield and biomass penalties were incurred

These trials continue to highlight the potential benefits that metribuzin tolerance could provide to lentils in the farming system, particularly in combination with IMI tolerance and as new varieties are developed with higher grain yields. The technology will have a fit on sandy soils, where the use of group 5(c) products applied post sowing pre-emergent can cause substantial crop damage, even at sub optimal application rates, and where there are specific weed problems that can be controlled with applications of metribuzin around sowing and/or in crop.

Sowing date and yield stability – faba bean and lentil

Several new faba bean varieties have been released or are due to be released with changes in agronomic traits such as flowering time and reproductive duration, disease resistance, and herbicide tolerance. Faba beans currently have limited uptake in drier Mallee regions. Early sowing, with early flowering varieties, combined with herbicide tolerance and agronomic practices, such as deep ripping, have the potential to open new opportunities. Similarly in lentil, varieties have been released, or are due to be released, with changes in agronomic traits such as plant architecture, biomass production, reproductive duration and timing, disease resistance, herbicide tolerance and pod retention. Changes in sowing date have the potential to maximise the benefits of these traits from a crop production and farming system perspective. There is interest in understanding the implications of later flowering with a reduced reproductive window, combined with lower vigour. In addition, the two new varieties GIA Sire and GIA Metro have unique growth habits that may require different planting densities to optimise grain yield.

Trials at Warne (central Mallee) and Kalkee (Wimmera in 2022) investigated phenological and yield responses to a range of sowing dates in faba bean and lentil. of the impact of plant densities on yield were also interrogated in lentils at Warne. All trials at both sites were severely impacted by waterlogging due to the very high rainfall in 2022. The Warne lentil trial was abandoned, with much of the trial waterlogged for around 6 weeks. Faba beans showed excellent tolerance to waterlogging with unanalysed grain yields ranging between 3.5t/ha and 5t/ha when sown 3 May, which was approximately 60% higher than the 2 June sown treatments (1.3t/ha and 2.5t/ha). Similar to 2021, AF14092 showed the highest grain yields of 5.06t/ha sown 3 May. At Kalkee, trials were more variable than Warne due to the combination of disease and waterlogging. Unanalysed faba bean grain yields ranged between 5.6t/ha and 8.0t/ha sown 14 April, 5.4t/ha and 7.6t/ha sown 23 May and 3.7t/ha and 5.3t/ha sown 28 June or 8 Aug with wide ranges between varieties demonstrating the importance of selecting phenology adapted to the right sowing opportunity. More information will be provided on varietal differences at the presentation. At both sites, disease was managed with a complete fungicide strategy (eight applications at Kalkee and three applications at Warne), aiming to minimise disease, as the aim of trials was to determine yield responses in the absence of disease. Despite the extreme disease (Botrytis grey mould) pressure, grain yield loss was minimised, which was highlighted at Kalkee where grain yields of 4–5t/ha were achieved with the susceptible variety PBA Bendoc. In contrast, many crops of this variety in the region close by struggled to achieve 2t/ha, with some crop failures.

In lentils at Kalkee, individual plot grain yields ranged from 0 to >6t/ha, highlighting the extreme variation due to waterlogging, disease and weed pressure. Generally, grain yields were highest when sown 23 May, with an average across all varieties sown of 3.3t/ha. When sown 14 April and 28 June, yields were 2.6t/ha and 2.7t/ha respectively, with yields from the late sown treatment (4 August) at 1.0t/ha. Detailed varietal responses will be discussed in the presentation following further analysis accounting for variation observed.

Disease management

In 2022, the importance of varietal resistance and a robust fungicide package (along with a little bit of luck) was highlighted.

Faba beans

Several trials in previous seasons have highlighted the benefits of newer fungicide products combined with using resistant varieties adapted to the cropping region (i.e., PBA Amberley in the high rainfall zone and PBA Samira in the medium to low rainfall zone). In 2022, trials in the high rainfall zone focused again on new chemistry and timing of application. Some key observations in the initial data were:

• waterlogging compounded disease severity, an observation which was corroborated by many growers, and resulted in considerable difficulties in timing of application for fungicides
• a spray strategy involving SDHI fungicides required fewer applications to provide similar or better level of disease control compared to conventional strategies with older chemistry. It also provided a longer window of coverage between applications, which is critical in high rainfall seasons where there are often limited opportunities for application.

Vetch

Botrytis grey mould has been a major issue in vetch, particularly in early sown crops and higher rainfall conditions, causing reduction in biomass production and hay quality. In addition, there are no varieties with high levels of resistance. In 2022, a small disease management trial was sown early (14 April) to compare the impact of canopy closure applications of carbendazim and Miravis® Star on disease development, biomass production and hay quality in four varieties (Studenica, Timok, Morava and Benetas) differing in growth patterns. In short, Miravis Star showed reduced disease intensity at 7 weeks after application compared with carbendazim (Table 3 and Figure 2) and resulted in improved biomass at the flat pod stage. This was particularly notable in the earlier variety, Studenica, where cuts were taken in early September and disease was just beginning to spread again in the Miravis Star treatment.

Due to the high rainfall, the disease epidemic progressed so that visual scores in the carbendazim treatments were similar to the ‘Nil’ on 2 September, while Miravis Star were about 40% lower than the ‘Nil’. At the end of September, all treatments had similar disease scores (data not shown). The progression of disease potentially explains why the relative biomass increase in other varieties was lower than observed in Studenica.

Figure 2. Botrytis grey mould symptoms in StudenicaA vetch 17 August 2022 following canopy closure fungicide sprays of carbendazim (applied 23 June 2022).

Table 3: Botrytis grey mould score (recorded 19 August) and biomass at early flat pod of vetch varieties in response to canopy closure fungicide application of carbendazim or Miravis Star compared with nil and complete control fungicide strategies at Kalkee in 2022.

1. Carbendazim (500mL/ha) and Miravis Star® (750mL/ha) were applied at canopy closure for each variety (23 June for StudenicaA, TimokA and MoravaA, 29 June for BenetasA). The nil treatment was unsprayed and the complete treatment had fungicides applied regularly to eliminate disease starting 10 June.

Soil constraints

Surface acidity, heavy alkaline clay subsoils and sandy soils are all constraints to pulse production in the newer pulse production area north of Nhill in the west Wimmera. Following work in 2021, it was identified that there is an opportunity to ameliorate these soils, particularly with deep ripping and the addition of an organic ameliorant to help overcome these constraints. A trial comparing lentil, chickpea and faba bean was sown near Yanac on a sandy soil with a heavy clay at 40cm. Ripping treatments (to 40cm) with and without the addition of composted cow manure (10t/ha) were applied. Similarly, in the expanding North Central area where sodic, acidic and saline soils constrain pulse growth, a trial was implemented at Mitiamo to investigate the effect of deep ripping, in combination with gypsum and other novel amendments applied at depth, on growth and yield of chickpea, lentil, vetch and field pea.

At Yanac, similar to previous observations on sandy soils, deep ripping prior to sowing lentil (cv. GIA Thunder) increased grain yield by 80% from 1.22t/ha in the unripped treatment to 2.20t/ha. The addition of cow manure as an amendment at depth, resulted in a further increase in yield, to 2.46t/ha. In faba bean (cv. PBA Samira), grain yield was increased by 44% from 3.33t/ha to 4.84t/ha by deep ripping, and to 5.27t/ha with the addition of cow manure. Ripping and amendment with the cow manure also resulted in a increase in nodulation and biomass (data not shown).

Unfortunately, the trial at Mitiamo was severely waterlogged and could not be harvested, however some key in season observations indicate potential for further investigation. Notably, biomass appeared to be improved with ripping and the addition of gypsum. Additionally, following the flooding event, the same treatments were observed to have survived longer before dying highlighting potential for the ripping plus gypsum to aid recovery in years of short duration temporal waterlogging stress.

Both these trials highlight further opportunities to expand pulse production as we overcome major soil constraints. In addition to the ripping and amendment research, the agronomy program is also working closely with breeding groups on identifying new varieties with improvements in tolerance to boron, soil acidity and adaptation to sandy soils. Combining these new traits with the improved agronomic management should continue to increase yield and yield stability of pulses.

Acknowledgements

The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and funding from GRDC, the authors would like to thank them for their continued support. This research was co-funded and delivered by Agriculture Victoria (DJP2105-006RTX) in partnership with SFS, BCG, Frontier Farming and FAR. We wish to thank the various pulse breeders from Grains Innovation Australia, Agriculture Victoria, NSWDPI and Adelaide University for their input. Thanks to technical staff for maintaining trials and collecting and entering data. Finally, we express gratitude to all our grower collaborators for the use of land and agronomists for invaluable support.

Useful resources

Brand J, Mawalagedera S, Manson J, Moodie M, Farquason L (2022) Agronomy best practices with pulses – Victoria. 2022 GRDC Updates, Bendigo.

2023 Victorian and Tasmanian Crop Sowing Guide

Contact details

Jason Brand
Agriculture Victoria
Grains Innovation Park, 110 Natimuk Road, Horsham VIC 3401
0409 357 076
jason.brand@agriculture.vic.gov.au
@JasonBrand