Key points

• Modelling the impact of drought of modern-day lentil  varieties showed substantially greater yield loss since the turn of the century
• Retained standing stubble improved both plant-available water and lentil yield
• PBA Jumbo2 grown on narrow rows with stubble retention demonstrated that a synergistic interaction between plant architecture, row spacings and stubble retention can deliver significant yield improvements

Matching lentil agronomy with shoot architecture traits can improve plant-available water and yield.

The timing, lower intensity and shorter duration of rainfall has been identified as a major constraint in most seasons in Victoria’s lentil growing districts as the prevalence of drought has also increased over the past two decades.

Consequently, a better understanding of the agronomic and varietal impacts on soil water retention will allow growers to maximise the benefit of any rainfall received.

With GRDC investment, Agriculture Victoria researchers are investigating crop water use under different agronomic systems and with architecturally different varieties.

Modelling the impact of drought on modern-day lentil varieties using the Agricultural Production Systems sIMulator (APSIM) showed substantially greater yield loss since the turn of the century. The average per-decade yield loss due to drought prior to 2001 ranged from 10 to 25 per cent, but has risen to more than 35 per cent in the past two decades.

In an on-farm experiment at Nhill in the western Wimmera in 2021, the impact of row spacing, stubble retention and variety selection on crop water availability, biomass accumulation and grain yield was measured.

Results clearly demonstrated the benefit of retained standing stubble in improving plant-available water (Figure 1) and lentil yield.

Figure 1: Plant-available water to 160-centimetre depth at three timings (eight-node, 14-node and flowering) under lentil crops sown at Nhill, Victoria, in 2021. Lentils were sown into either standing or slashed stubble with either narrow (19.1cm) or wide (38.2cm) row spacing.

Source: Abeya Tefera.

Lentils were sown narrow or wide row onto retained narrow-row stubble. In general, the lentil row-spacing treatments had little effect on soil water; however, when stubble was retained, the narrow spacings (19.1 centimetres) produced a higher yield than the wide (38.2cm). This is likely because the retained stubble in the narrow-row spacings provided a more-effective trellis for the lentils, potentially improving light interception and reducing losses to shattering.

As expected, the higher-yielding variety PBA Jumbo2 consistently outperformed PBA Bolt.

The highest-performing treatment was PBA Jumbo2 grown on narrow rows with stubble retention. This suggests that a synergistic interaction between plant architecture, row spacings and stubble retention can deliver significant yield improvements. This treatment gave the sprawling PBA Jumbo2 maximum advantage, allowing it to produce a better stand.

Soil measurements found more plant-available water under PBA Jumbo2 in the early growth stages than under PBA Bolt. The sprawling habit of PBA Jumbo2 is thought to more-effectively shade the soil and prevent early season evaporation losses.

The 2021 season had a dry start that slowed early growth. However, this was followed by higher-than-average rainfall during July, September and October. This type of season would limit the impact of these treatments (row spacings/stubble retention), yet there were still significant differences.

A normal opening to the season would likely enhance the ability of PBA Jumbo2 to hinder soil-water evaporation through more-vigorous early growth, while drier months through the middle of the season would exacerbate the differences between agronomic treatments.

The impacts of water stress, including heat, frost and soil-related factors, will be further assessed on a large scale using crop growth models to identify opportunities to improve yield through interactions between agronomic practices and traits related to phenology and architecture.

This could be used as a decision-making tool by growers, breeders and agronomists to improve lentil productivity.

More information: Dr Garry Rosewarne, 0477 616 759, garry.rosewarne@agriculture.vic.gov.au