Agronomy best practices with pulses - Victoria

Take home messages

• Higher than average grain yields were observed throughout Victoria (VIC), with highest on record being observed in some areas. Lentils and chickpeas often proved to be the most profitable crops on-farm with excellent grain prices.
• Similar to previous years, PBA Jumbo2 performed extremely well in 2016, highlighting its yield stability across both dry and wet seasons. It is a variety that reduces disease risks and benefits from sowing early to maximise yield potential. Potential net returns, based on yields in the Curyo trial in 2016, were approx. $2,500/ha.
• Similar to 2015, seeding rate of higher biomass new lentil varieties could be lowered from 120 to 80 plants/m², particularly those with disease resistance sown early. Lower seeding rates also helped minimise botrytis grey mould in susceptible varieties, reducing potential yield losses. Delayed sowing, such as in June, will still require the current recommended sowing rate of 120 plants/m².
• New faba bean lines will offer opportunities for growers in the Mallee with profitable yields (>140% of PBA Samira) produced in both dry (2015) and wet (2016) seasons.
• The virulence of the new isolate of ascochyta blight in chickpeas was assessed at Curyo and Rupanyup and confirmed to cause significant symptoms (including stem breakages) on all varieties and breeding lines. Grain yield loss in the most susceptible varieties and breeding lines was up to 100%, however the level of resistance in a number of kabulis including Genesis™090, means that the disease can be proactively managed with fungicides to produce profitable grain yields.

2016 Seasonal snapshot

• Pulse grain yields across all rainfall zones were higher than average in 2016, with record yields observed in some areas, particularly where waterlogging was not a major issue. Lentils were a highlight with yields exceeding 3t/ha in many areas of the Mallee and Wimmera and grain prices, remaining strong at approx. $600-$700/t, resulting in a highly profitable crop.
• Most crops were sown into a moist seed bed, except in the central and northern Mallee which were dry. Good rainfall throughout May and warm conditions ensured establishment and early growth were generally excellent. Annual and growing season rainfall was between 20% and 35% greater than long term averages at Southern Pulse Agronomy (SPA) research sites. More than 100mm was recorded during September at all sites and more than 50mm in October. At Curyo in the southern Mallee, there was 180mm rainfall between 1 September and 5 October. Waterlogging resulted in the loss of several field pea trials which were under more than 20cm of water. Waterlogging also impacted trials at the central Mallee (Ouyen) and Wimmera (Rupanyup) trial sites. There were no major heat or frost events that affected the trials, although cool conditions during the reproductive phase meant that flower and pod abortion occurred in beans and chickpeas. The warmer conditions early in the season also meant that large canopies were produced, conducive to disease. There were reports of a late light frost which may have impacted on lentil yields in parts of the Wimmera.
• Due to the extremely wet conditions, disease was a major issue in 2016, and difficult to control, due to fungicide shortages and lack of suitable spraying conditions. In lentils, a low level of ascochyta blight was noted earlier in the season. Botrytis grey mould became a major issue as the season progressed, with susceptible varieties showing significant crop damage despite attempts of control with fungicides. On review, waterlogging is likely to have caused greater yield loss than disease in lentils with crops on heavier poorly drained soils showing up to 70% yield loss. In comparison, it was estimated that yield losses of up to 1.5t/ha (50%) were experienced from disease. In chickpeas, the new isolate of ascochyta blight was seen early, but was generally well managed by growers throughout the season, resulting in little yield loss. In comparison at a trial site where disease was not controlled, it resulted in complete yield loss in susceptible varieties. In faba beans, chocolate spot was significant and is likely to have caused yield losses in crops where it was not adequately controlled. Further detailed discussion of disease issues in pulses is published in a related update paper.

Agronomic research highlights

Building on the success of previous lentil research by SPA and Pulse Breeding Australia (PBA), which focused on improving and understanding Group B herbicide tolerance in lentils, a SARDI pre-breeding project has developed Group B tolerant faba bean and Group C tolerant lentil germplasm. Previous agronomic field trials in SA and VIC in 2014-2015 confirmed faba bean germplasm lines with tolerance to a range of imidazolinone (Imi) chemistries. In 2016, a trial was held at Rupanyup with an advanced herbicide tolerant (HT) breeding line, the best HT germplasm line from the previous experiments, the faba bean variety Nura and the HT lentil variety PBA Hurricane XT. This trial again demonstrated the high level of Imi tolerance in the HT germplasm line and also in the advanced breeding line with only minimal crop damage and no significant yield loss recorded to a range of Group B herbicides (Table 1 and 2). Research will continue in coming seasons as the management package for a new high yielding and herbicide tolerant variety is developed.

¹Application time: Res — applied to mimic residual concentrations. PEb — applied at 4-5 node stage of crop growth.

In addition, a very high level of metribuzin tolerance (10-20 times) has been confirmed in lentil germplasm in field validation trials in VIC and SA from 2014-16. This material has now been ‘crossed’ with Group B tolerant lines with the aim of developing dual herbicide tolerant (Group B+C) varieties. Further agronomic research will continue in coming seasons with these novel lines and new herbicide tolerant kabuli and desi chickpea material, to ensure best practice agronomic packages are delivered to growers on release of new varieties.

Opportunities to optimise seeding rates and sowing dates in lentils

Higher yielding lentil varieties has been released, with improvements in agronomic traits including biomass production, lodging resistance, disease resistance, herbicide tolerance, maturity and pod retention. In addition, growers are sowing crops earlier to maximise yield potential and reduce risks of heat and terminal drought stress. Research in 2016, similar to 2015, focused on identifying potential advantages of lower seeding rates for these new varieties and its interaction with sowing date, without incurring yield penalties. Several new breeding lines were also compared at the traditional sowing rate of 120 plants/m².

The combination of high rainfall and large canopy development in lentils led to a moderate to severe outbreak of botrytis grey mould at both the Curyo and Rupanyup trial sites. No fungicides were applied to these trials to ensure a clear understanding of the relative resistance of varieties and breeding lines under high disease pressure. No disease was observed at the Ouyen trial site.

In seeding rate trials at Rupanyup, there was a significant interaction between plant density and botrytis grey mould intensity (Figure 1). When sown 13 May,  the moderately susceptible (MS) breeding line CIPAL1301 showed increasing levels of disease as plant density was increased. This correlated to decreasing yield with increased plant density, from 4.08t/ha at 40 plants/m² to 2.90t/ha at 200 plants/m². In comparison, PBA Jumbo2 had a smaller reduction in yield at the highest sowing rates from 4.36t/ha at 40 plants/m² to 3.96t/ha at 200 plants/m². When sown 15 June,  CIPAL1301, still showed increasing levels of disease as plant density was increased, but this did not correlate with grain yields, which were not significantly different across sowing rates. PBA Jumbo2 showed highest yields at the 160 plants/m² treatment. Similar trends across varieties and rates were observed at the Curyo site (data not shown).

Figure 1. Botrytis grey mould disease score (0 — no disease; 100 — dead) and grain yield of CIPAL1301 and PBA Jumbo2 sown at five seeding rates and two sowing dates at Rupanyup in 2016.

In the sowing date trials at Curyo, botrytis grey mould disease scores were generally higher in the plots sown 4 May compared with those sown 2 June (Figure 2A). PBA Jumbo2 showed no obvious symptoms of disease at either sowing date consistent with its resistance rating of ‘R’. PBA Blitz, PBA Greenfield and the breeding line CIPAL1422 also showed little or no disease consistent with their moderately resistant (‘MR’) rating for botrytis grey mould. The susceptible (S) variety PBA Bolt (rated ‘S’ for botrytis grey mould) and breeding line L5 were generally the worst affected.

Grain yields ranged between 1.75 and 4.04t/ha at Curyo, 1.82 and 3.32t/ha at Ouyen and 2.47 and 4.19t/ha at Rupanyup. Relative rankings of varieties varied between sowing dates and sites (Figure 1B, only Curyo and Ouyen shown for illustration). At Curyo, PBA Jumbo2 was the highest yielding variety sown 4 May (4.04t/ha) and 2 June (3.40t/ha), but at Ouyen, its yield was mid-range (2.63t/ha) and significantly less than the breeding line L5 (3.32t/ha). Conversely, L5 was the lowest yielding line at Curyo (1.75t/ha, 4 May and 2.37t/ha, 2 June) indicative of its susceptibility to botrytis grey mould. PBA Bolt also performed relatively poorly due to its susceptibility, with yields 50% and 22% less than PBA Jumbo2 at Curyo sown 4 May and 2 June, respectively. At Ouyen, it was notable that PBA Hurricane XT was the highest yielding of the released varieties, similar to PBA Ace and PBA Jumbo. This may indicate differential tolerance to soil types as the soil was significantly sandier than at Curyo and no group B chemicals had been used at that site for several years. It has been observed in industry that PBA Hurricane XT appears to perform better than other varieties over sand hills. Further work is planned to investigate potential adaptation. At Rupanyup, similar trends to Curyo for  botrytis grey mould and grain yields were observed (data not shown).

Results have highlighted the yield stability of a number of lentils, particularly PBA Jumbo2, which similar to previous seasons performed extremely well in 2016, highlighting its yield stability in both dry and wet conditions. It is a variety that reduces disease risks and benefits from sowing early to maximise yield potential. Potential net returns, based on yields in the Curyo trial in 2016, were approx. $2,500/ha. Other varieties, with lower disease resistance ratings may benefit from delayed sowing where fungicide management of disease can be difficult.

Disease management is critical to maximise yield and quality, particularly varieties with resistance ratings less than ‘R’. Applying the appropriate preventative fungicide early and just prior to canopy closure reduces disease pressure and losses. It is estimated that in the susceptible variety, botrytis grey mould resulted in a yield loss of 1-1.5t/ha ($650-$975/ha).

Similar to 2015, lowering the seeding rate of lentils from 120 plants/m² to 80 plants /m² is viable, particularly with early sowing and the use of varieties such as PBA Jumbo2, but significant yield reductions have been observed in drier seasons below 80 plants/m² and with delayed sowing. It is important that lower seeding rates are only utilised in paddocks where minimal weed competition is expected.

Figure 2. Botrytis grey mould disease score (0 — no disease; 100 — dead) (A) and grain yield (B) of lentil varieties and breeding lines sown at two sowing dates at Curyo and one date at Ouyen (grain yield only as no disease present) in 2016. All named varieties are PBR varieties.

Faba beans in the Mallee

The performance of several new faba bean lines identified for improvements in drought resistance was again excellent at Curyo in 2016 (Table 3). All of the ‘AF12-‘series lines had higher grain yields than PBA Samira (4.12t/ha), except AF12038, with AF12025 (5.75t/ha) achieving 140% of PBA Samira.   AF12025 was also the highest yielding line in the drought conditions of 2015. In addition, the beans were the best of the pulses in tolerating waterlogging at Curyo and displayed very high biomass, meaning nitrogen (N) fixation was likely to be extremely high (estimated to be 200-300kg/ha).

A sowing rate experiment compared AF012025 and PBA Samira at densities ranging from 5-30 plants/m². Consistent with recommendations, 20 plants/m² was the optimum density to maximise grain yield in beans (Figure 3).

Similar trials were sown at Ouyen and Rokewood, but unfortunately at Ouyen there were issues with equipment, resulting in variable establishment and missing rows, meaning trials could not be analysed. Despite all the issues, it was estimated that beans had grain yield between 2-3t/ha. Data from Rokewood was being analysed at the time of paper submission.

Figure 3. Average grain yield (t/ha) of faba beans at various plant densities at Curyo in 2016.

Ascochyta blight in chickpeas

At Curyo in late July, a significant outbreak of ascochyta blight was observed in all chickpea trials (Table 4). Symptom assessment indicated that this isolate of ascochyta was the same as observed in 2015, having virulence on resistant lines such as Genesis™090 and PBA Slasher. Stem breakages were observed in all varieties and breeding lines, with symptoms scores ranging from 4.8 for CICA1454 to 9.0 for PBA Striker and Howzat (plots dead). Genesis™090 was moderately susceptible with a score of 6.3. It was also noted that most of the susceptible to very susceptible varieties and breeding lines were a desi seed type, while the most resistant varieties and breeding lines were a kabuli type (Table 4). Despite the high levels of disease observed, several varieties and breeding lines were able to partially recover during November and December to produce adequate grain yield (Table 4). Disease scores were generally well correlated with the relative yield loss observed. The yields in the fortnightly fungicide treatments were lower than could be expected given the rainfall, ranging from 2.06t/ha for Neelam to 0.99t/ha for Genesis™Kalkee. This is likely to be related to the excessive biomass that was produced prior to flowering, waterlogging and ongoing cold conditions during the reproductive phase, which meant many flowers and pods were aborted. The desi varieties were generally higher yielding than the kabulis.

In the ‘nil’ fungicide treatment, grain yields ranged from 1.48t/ha for CICA1454 to zero for Howzat and PBA Striker. All desi varieties and breeding lines suffered yield losses greater than 70%, except c3 at 25%. Conversely, many kabulis showed no statistically significant loss, although for all varieties and breeding lines, except Genesis™Kalkee and CICA1454, yields were less in the ‘nil’ treatment compared with ‘fortnight fungicide’. The results highlight the ability of chickpeas to recover from disease, once conditions dry out. In addition, the disease reduced leaf area and biomass and delayed pod set, thus resulting in yields similar to the fortnightly treatment for some varieties and breeding lines. Further assessment is ongoing to understand the impact of ascochyta blight on seed quality.

A similar trial was conducted at Rupanyup and with analysed data available at the updates.