Agronomy best practices with pulses – Victoria

Take home messages

• Several new lentil varieties will offer growers improved grain yield and yield stability combined with a range of novel herbicide traits.
• Weed management and herbicide traits – several new traits in a range of pulse crops will offer alternative weed management strategies in the future.
• Frost in lentil — significant variation was observed across varieties, with PBA Hurricane XT^A showing the worst vegetative damage of released varieties and PBA Ace^A showing good tolerance. Generally, standing stubble treatments showed less damage than slashed stubble, and row spacing and sowing direction had little effect).  Increased vegetative damage resulted in reduced grain yields.
• Deep ripping in pulses, except lupin - grain yield benefits from deep ripping on deep Mallee sands of 100-210%, resulting gross margin gains of $312-$668/ha have been recorded.
• Faba beans in the high rainfall zone — the greatest grain yield achieved at Vite Vite North in 2021 was 9.2t/ha, with PBA Samira sown on April 16 at 28 plants/m2. Higher plant numbers increase biomass, but additionally contribute to faba bean grain yield potential by increasing the number of potential pods and seeds, in a similar manner to head number in cereal crops. Chocolate spot management was improved in 2021 with genetic resistance and fungicides, but yield benefits of improved chocolate spot management were not realised with reduced plant density.

Potential releases and new varieties

Two new imidazolinone (IMI) tolerant lentils (GIA2002L, GIA2003L), the first imidazolinone (IMI) tolerant lentil with improved tolerance to clopyralid soil residues from a prior crop (GIA1703L) and the first imidazolinone (IMI) tolerant lentil with metribuzin (MET) tolerance (GIA2004L) are potentially available in 2022.

A new high yielding ‘Blue’ field pea (PBA Noosa^A) and ‘Kaspa’ type (PBA Taylor^A) are available for production in 2022. In addition, field pea with improved tolerance to common in-crop and residual Group B herbicides is available (GIA2005P).

Varietal performance in agronomic trials

In lentils, all the potential new varieties were sown in trials at Curyo (southern Mallee), comparing sowing dates (Table 1), and Propodollah (west Wimmera), comparing soil types (Table 1). GIA2002L had the highest or equal highest grain yield in all trials, highlighting good potential yield stability. GIA2003L was consistently high yielding, but slightly less than GIA2002L. GIA1703L had excellent yields at Curyo, similar to 2020, and on the ripped sand at Propodollah, but was slightly lower on the duplex soil, it is hypothesised this was due to frost damage that occurred in this location adversely affecting this breeding line more than others. GIA2004L was relatively low yielding in trials this year, and results need to be treated with caution, as some terbuthylazine damage was observed and this breeding line has known increased sensitivity compared with other varieties.

Further details on trials including field peas, seasonal conditions and outcomes will be explored in the presentation.

Table 1: Grain yield (t/ha) of lentil varieties and breeding lines in 2021 grown in a sowing date trial at Curyo (southern Mallee) and in a soil type comparison trial at Propodollah (west Wimmera) comparing duplex soil (sandy loam topsoil and clay subsoil) with a sand that had been ripped in 2018.

Variety/Breeding Line	‘Curyo’ Sowing Date				‘Propodollah’ Soil Type
	Apr 29	Jun 01	Ave		Duplex Flat	Ripped Sand
GIA2002L	2.68	2.39	2.54		2.14	2.19
GIA2003	2.65	2.40	2.53		1.87	1.86
GIA1703L	2.64	2.29	2.47		1.61	1.90
CIPAL2121	2.57	2.35	2.46		2.07	2.10
GIA LeaderA	2.55	2.34	2.45		1.84	2.00
PBA Jumbo2A	2.38	2.49	2.44		1.87	2.08
PBA HighlandXTA	2.49	2.35	2.42		1.67	1.91
PBA AceA	2.49	2.32	2.41		2.12	1.46
CIPAL2122	2.36	2.35	2.36		1.75	2.01
GIA2001	2.50	2.21	2.36		1.75	1.70
PBA Hurricane XTA	2.48	2.23	2.36		1.66	1.24
PBA Hallmark XTA	2.48	2.03	2.26		1.43	1.82
PBA BoltA	2.48	2.01	2.25		1.75	1.52
PBA KelpieXTA	2.28	2.21	2.25		1.73	1.63
NipperA	2.46	2.02	2.24		1.24	1.37
GIA2004L	1.76	1.33	1.55		0.64*	0.20*
Ave	2.45	2.21	2.33		1.70	1.69
Lsd (P<0.05)	Sow Date = 0.12; Variety = 0.22; Sow Date x Variety = NS				0.42	0.61

*Trial showed damage related to terbyne. The low yield of GIA2004L was a result of increased sensitivity to terbyne compared with other varieties.

Agronomic research highlights

Novel herbicide traits, weed management and new herbicides

In lentils, there are a number of potential new varietal releases combining tolerance to the imidazolinone herbicides with tolerance to metribuzin or soil residues of clopyralid. These will offer alternative weed management strategies within the farming system. In 2021, trials in the Wimmera and southern Mallee assessed potential herbicide strategies on vetch control in lentil and field pea varieties utilising novel herbicide resistance traits and any resulting impacts on grain yield. At the point of publication, data from trials is still being analysed, however early observations indicate that in the absence of herbicides, competition from vetch in lentil caused approximately 60% reduction in grain yield. In comparison, a conventional herbicide strategy reduced yield loss from vetch competition to 23%, while a strategy incorporating the use of imidazolinone chemistry over varieties and lines with the tolerance trait showed no yield loss from vetch competition. Despite improvements in relative grain yield, neither conventional nor imidazolinone based strategies completely prevented vetch seed set. Both potential herbicide management strategies utilising tolerance to metribuzin or soil residues of clopyralid showed improved control of vetch.

In faba beans, a new line AF14092, has shown improved tolerance to metribuzin applied post-sowing pre-emergent compared with PBA Samira^A in field trials near Horsham. This breeding line showed excellent grain yields throughout Victoria and could provide improved crop safety to metribuzin when applied post-sowing pre-emergent across a range of soil types.

There has been much interest in the new Group 14 herbicide Reflex (240g/L fomesafen) as an alternative to Group 5 herbicides to assist with pre-emergent broadleaf weed control in pulse crops. Observations so far indicate that label guidelines to maintain separation between herbicide treated soil and planted seed are critically important when used in lentils grown on sandy soils, such as in the Mallee. There is a high risk of movement of treated soil into the crop row on these soils which can occur through soil throw from excessive sowing speed, collapse of the furrow side wall, soil drift and erosion and rolling. Actions should be taken to mitigate these potential issues, especially in situations where the soil is soft and or has low ground cover such as on deep sandy dunes or where soil amelioration such as deep ripping has recently been completed.

Frost in lentil

In lentil trials at Propodollah in 2021, several major vegetative and reproductive frost events occurred. Crop chlorosis and necrosis (yellowing) in response to two vegetative frost events (26 August: -2.2OC and 27 August: -2.9OC) was recorded. Substantial variation was observed across varieties, with PBA Hurricane XT^A showing the worst damage of released varieties and PBA Ace^A showing good tolerance (Figure 1). Generally, standing stubble treatments resulted in less visually observed damage than slashed stubble (Figure 2) and row spacing and sowing direction had little effect (data not shown). Previously it has been suggested that the vegetive frost symptoms were not related to grain yield, however preliminary analysis from these trials have shown a significant correlation between observed crop damage and reduced grain yield.

In addition, there was a frost event during the reproductive phase events (11 October: -0.8OC and 12 October: -0.8OC) that caused significant flower and seed abortion. Detailed assessments of flower and pod loss showed that the relative effect across a range of varieties was similar (data not shown). While in some varieties flower and pod loss were higher, they respectively set more flowers and pods to compensate.



Figure 1. Frost damage (% crop yellowing), recorded 31 August, on lentil varieties and breeding lines grown at Propodollah (west Wimmera), from two vegetative frost events (26 August: -2.2OC and 27 Aug: -2.9OC).



Figure 2. The effect of stubble on frost damage (% crop yellowing), recorded 31 August, in lentil varieties grown in a trial comparing stubble, row space and row direction at Propodollah (west Wimmera) fromtwo vegetative frost events (26 August: -2.2OC and 27 August: -2.9OC).

Soil amelioration

Trials located on deep Mallee sands over the past three seasons have demonstrated substantial increases in the grain yields of pulse crops in response to soil amelioration practices such as deep ripping (Figure 3). Chickpea and faba bean were the most responsive pulse crops to deep ripping in summer prior to sowing, with an average yield increase of 210% across all trial sites. Deep ripping providing a mean yield benefit in lentils of 166%. Deep ripping doubled the mean grain yield of field peas and vetch in the first year following deep ripping. In contrast to the other grain legumes, deep ripping provided only a small yield benefit in lupin. Lupins also have the highest establishment risk in sand due to their requirement for shallow seed placement, therefore lupins should not be sown into deep ripped paddocks in the first season post-amelioration.

A gross margin analysis showed that the average yield response observed across the trial sites was highly profitable (Table 2). The average chickpea yield response to deep ripping was 1.1t/ha and this would have improved gross margin by approximately $667/ha, after accounting for an annualised cost of deep ripping of $40/ha. Field pea and faba beans responded to deep ripping treatments with a similar yield boost, which led to more than $360/ha profit. The average yield response to deep ripping of lentil and vetch was lower at 0.5t/ha, but this still led to approximately $300/ha gross margin. Lupin was the only pulse crop that did not gain an economic benefit from deep ripping in these trials. The profitability of the farming system is also likely to be improved with subsequent cereal crops benefiting from increased nitrogen supply from the improved pulse biomass production and legacy effects from the deep ripping operation.

While these trials have shown large productivity and profitability benefits, growers considering deep ripping must evaluate operational risks. For example, deep ripping before a pulse phase should be targeted to paddocks with high levels of residual stubble to ensure adequate ground cover is maintained and minimise erosion risk, while care also needs to be taken with pre-emergent herbicides to minimise risk of crop damage. Trafficability of heavy machinery is also an issue that needs to be managed post-ripping, with rolling with heavy steel drum rollers recommended to reconsolidate the surface and provide better flotation for the seeder and self-propelled sprayers.



Figure 3. Grain yield of pulse crops grown on deep Mallee sands for non-ripped and deep ripped treatments. Data is a collation of six Mallee trial sites conducted between 2019-2021. All deep ripping treatments used a Tilco A66 tines spaced at 56cm apart with a ripping depth of 400-500mm.

Table 2: Partial gross margin of the average deep ripping yield benefit for pulse crops grown on deep sands across six Mallee trial sites from 2019—2021. Prices used in the gross margins are the average January grain price from 2020—2022 for each pulse crop, with gross margins calculated using an annualised cost of ripping of forty dollars per hectare.

Crop	Average Yield Benefit (t/ha)	Average Grain Price ($/t)	Gross Margin Benefit ($/ha)
Lentil	0.5	703	312
Chickpea	1.1	643	668
Narrow Leaf Lupin	0.1	486	7
Field Pea	1.0	427	387
Vetch	0.7	533	333
Faba Bean	0.9	449	364

Pulse nitrogen value

The value of pulses in cropping rotations is well documented, with average yield benefits of wheat following a crop legume 1.2t/ha higher than wheat on wheat (Angus et al. 2015). In addition to providing a break option for managing cereal disease and weed control options, they provide N rich crop residues which gradually become available to the following crops.

Figure 4 shows pulse crops, on average, fix between 21(lupin) and 35 (vetch) kg of crop N per tonne of dry matter produced, which equates to $31-$52/t dry matter (based on a urea price of $AU675/t). The total amount of nitrogen fixed by the crop is largely driven by dry matter production and generally farming practices which optimise pulse biomass production will also optimise N-fixation. For example, a 4t lentil crop on average would fix 100kg N/ha compared to an 8t bean crop which would fix in the order of 200kg/ha.

There is significant variation around the average N-fixation values, indicating considerable room for improvement overall. Research continues to improve inoculation and agronomic practices in order to optimise N-fixation in cropping systems.



Figure 4. The average crop nitrogen (shoots + roots) per tonne of dry matter (shoots at mid pod fill) for each of six pulse species was estimated using around 1700 data points (n) from field trials conducted in the southern region between 2015-2020 (Farquharson and Ballard, 2022 unpublished). The standard deviation for each of the species is shown. The mean value of nitrogen was calculated based on the 12-month average (2021) urea price of $AU675/t. The contribution of N in roots was estimated using root factors from Unkovich et al. (2010).

Faba beans in high rainfall zone

Grain yields of early-sown faba beans were limited by plant density, not biomass

The highest grain yield from faba bean trials at Vite Vite in 2021, was 9.20t/ha in PBA Samira^A sown 16 April at 28 plants/m2. In a sowing date trial comparing a range of varieties, biomass was not related to grain yield in earlier sown treatments (April 16 & 30), but highly correlated at the late sown treatments (May 21; Fig 5). In a related trial investigating the interaction between plant density and sowing date, grain yield of PBA Samira increased as plant density was increased from 7 to 28 plants/m2 for both sowing date of April 16 or April 30. It is therefore hypothesised that the yield potential of early-sown faba beans was limited by plant number, not biomass.



Figure 5. The relationship of biomass to grain yield of eight faba bean varieties sown on three sowing dates at Vite Vite North, Victoria.

Lower plant density did not reduce chocolate spot severity

Chocolate spot management was improved in 2021 by use of genetic resistance (+25% grain yield from S to MRMS, no fungicides) and fungicides (+50% grain yield from nil to complete control). A reduction in plant density reduced chocolate spot symptoms, but also resulted in 30% lower grain yield (Figure 6).

Grain yield benefits of higher plant densities are usually realised when disease is kept under control and/or when the advent of disease occurs in late spring. For instance, in 2021, chocolate spot infection began in late September, around the time of pod emergence, but in 2020 infection began in early August (unusually early). In 2020, grain yield was unaffected by plant density treatments. This would suggest that when chocolate spot is not controlled, benefits to having higher plant density are realised if disease incursions begin in mid-spring (as in 2021, Figure 6), but not realised if disease incursions begin in early spring (as in 2020).



Figure 6. The relationship between grain yield and plant density of PBA Amberley and PBA Bendoc managed with (complete DM) and without fungicides (no DM) at Vite Vite, Victoria in 2021. Significant differences indicated with letters. Percentage reduction in grain yield due to lower plant density in bold.

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 author 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 the thank the input of various pulse breeders from Grains Innovation Australia, Agriculture Victoria and Adelaide University. Thanks to the 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.

References

Angus JF, Kirkegaard JA, Hunt JR, Ryan MH, Ohlander L, Peoples MB (2015) Break crops and rotations for wheat. Crop and Pasture Science 66(6), 523-552.

Unkovich MJ, Baldock J, Peoples MB (2010) Prospects and problems of simple linear models for estimating symbiotic N2 fixation by crop and pasture legumes. Plant and Soil 329(1-2), 75-89.

2022 Victorian Crop Sowing Guide (2021)

Contact details

Jason Brand
Agriculture Victoria
Grains Innovation Park, 110 Natimuk Road, Horsham VIC 3400
0409 357 076
jason.brand@agriculture.vic.gov.au
@JasonBrand