Opportunities to improve the productivity and reliability of pulse crops grown on sandy soils in the SA Mallee

Opportunities to improve the productivity and reliability of pulse crops grown on sandy soils in the SA Mallee

Take home messages

  • In trials conducted near Loxton in 2022 and 2023, deep ripping sandy soil increased pulse yields by 30–80%.
  • Deep ripping only benefited pulse production on the deep sandy soil on the dune and there was no benefit from deep ripping the clay loam–loam soils located in the swales.
  • Lentils were responsive to high rates of phosphorus fertiliser inputs on soil types which soil testing identified as having low soil phosphorus levels.
  • The post-emergent application of 280g/ha of metribuzin to GIA Metro had no impact on grain yield in 2023 (PER92810).
  • GIA Thunder was 25% higher yielding than GIA Metro. In situations where there are substantial weed burdens, the yield difference between the two varieties may be less if post-emergent applications of metribuzin can improve weed control.

Background

Pulse crops are an increasingly important component of Mallee cropping sequences. As pulse production expands into non-traditional regions, such as the Mallee, challenges have been encountered related to growing pulses on sandy soils. Through the GRDC project ‘Development and extension to close the economic yield gap and maximise farming systems benefits from grain legume production in South Australia (SA)’, Frontier Farming Systems has been trialing strategies to improve the productivity and reliability of legume crops grown in low rainfall regions, such as the SA Mallee.

The productivity and reliability of pulses grown on the deep sandy soils within paddocks remains a major constraint to pulse production in the Mallee. Deep ripping has been shown to increase the growth and yield of pulse crops by up to 300% on these deep sandy soils. Trials through this project looked to explore which other soil types might benefit from deep ripping and if the benefits can be enhanced through additional nutrition inputs.

As lentils increase in frequency in Mallee rotations, broadleaf weeds are becoming an increasing issue. A new lentil variety, GIA Metro, combining metribuzin tolerance with the imidazolinone tolerance is now available. In addition, metribuzin is permitted for in-crop application specifically in such varieties via APVMA permit PER92810. The use of metribuzin individually and in combination with other registered herbicides in-crop could improve the control of problem weeds in lentils grown in tight rotations or on soil types where use of residual Group 5 products can cause substantial crop damage, even at suboptimal rates.

Method

Deep ripping and nutrition inputs

Separate trial sites were established near Loxton in 2022 and 2023. In 2022, trials compared nutritional treatments for lentil and chickpea grown with and without deep ripping. The trial was replicated on two soil types within the paddock: A deep sandy soil located on the top of a dune, and a loam soil located in the swale between sandy dunes. There were five nutrient treatments (Table 1), and deep ripping treatments were implemented to a depth of 50cm using Tilco straight shank tynes.

In 2023, a similar trial was repeated at a new site near Loxton, however only lentils were grown and there were six sub-trials, which transitioned across a 70m transect from the clay loam soil on the swale to the deep sandy soil located on the top of a dune. Nutrition and deep ripping treatments were the same as the 2022 trial (Table 1).

Table 1: Nutrition treatments applied to lentil (2022 and 2023) and chickpea (2022 only)t Loxton in 2022 and 2023.

Treatment no.

Treatment description

MAP (Banded)

SOA (banded)

Liquid inject

(in furrow)

Liquid foliar

1

Nil

Nil

 

b

2

MAP (Low)

25kg/ha

 

3

MAP (High)

50kg/ha

 

4

MAP (High) + SOA

50kg/ha

50kg/ha

5

MAP (High) + SOA + ZMC + Mo

50kg/ha

50kg/ha

Sipcam Multisol @ 8L/ha + Sipcam Amino Boss Moly @ 0.8L/ha

Sipcam Amino Boss ZMC @ 4L/ha + Sipcam Amino Boss Moly @ 0.8L/ha

Metribuzin tolerant lentils

A trial site at Loxton in 2023 compared the performance herbicide tolerant (HT) lentil varieties GIA Metro and GIA Thunder. The two varieties were grown with and without the following herbicides applied:

  • District practice (DP) (Group 5 herbicide Incorporated by  Sowing (IBS)
  • Intercept® (750mL/ha) applied post emergence (PE) at the 6-node growth stage.

Additionally, metribuzin (280g/ha) was also applied PE at the 6-node growth stage to GIA Metro only, as permitted under the APVMA permit PER92810.

Results and discussion

Deep ripping and nutrition inputs

The 2022 season was one of the wettest on record at Loxton with 480mm of rainfall received for the season, with the spring period being especially wet with 290mm falling in September–November. Despite an abundance of soil moisture, deep ripping had a large impact on the productivity of lentil and chickpea grown on the sand dune soil (Figures 1 and 2). The benefit from deep ripping was consistent across both crops, with an extra 1.2t/ha of grain grown. However, deep ripping was not beneficial to either crop on the loam soil. There were also benefits from nutrition treatments in lentils, however chickpeas were not responsive to any nutrient treatment on either soil type (Figure 2). There was a 0.7–0.8t/ha grain yield benefit in lentils in treatments where 50kg/ha MAP was applied, relative to no fertiliser. Across both soil types, the rate of return from MAP inputs was 15kg of grain for each kilogram of fertiliser applied. Soil phosphorus (P) was low on both soils, with Colwell P levels of 11mg/kg and 13mg/kg measured for the loam and sandy soils, respectively. Therefore, benefits from the application of P were predicted from the soil tests. The application of trace elements did not influence the productivity of lentils and chickpea.

Lentil grain yield response in 2022 to deep ripping and nutrition inputs on the sandy soil type (left) and loamy soil type (right). Error bars represent the 95% confidence interval.

Figure 1. Lentil grain yield response in 2022 to deep ripping and nutrition inputs on the sandy soil type (left) and loamy soil type (right). Error bars represent the 95% confidence interval.

Chickpea grain yield response in 2022 to deep ripping and nutrition inputs on the sandy soil type (left) and loamy soil type (right). Error bars represent the 95% confidence interval.

Figure 2. Chickpea grain yield response in 2022 to deep ripping and nutrition inputs on the sandy soil type (left) and loamy soil type (right). Error bars represent the 95% confidence interval.

Deep ripping at the 2023 site again improved the grain yield of lentils (Figure 3), but only on the sandiest soils located on mid-slope and top of the sandy dune. These soil types had a soil texture with more than 80% sand in the top 60cm of soil. Lentil yields were very low (<0.5t/ha), however deep ripping increased grain yield by 0.1–0.2t/ha, which represented a 30–80% improvement.

Grain yield of lentils with and without deep ripping grown across soil types transitioning from a clay loam soil in the swale to a deep sandy soil on top of a dune in a Mallee paddock near Loxton in 2023. Error bars represent the Lsd at each landscape position (p<0.05).

Figure 3. Grain yield of lentils with and without deep ripping grown across soil types transitioning from a clay loam soil in the swale to a deep sandy soil on top of a dune in a Mallee paddock near Loxton in 2023. Error bars represent the Lsd at each landscape position (p<0.05).

There was a grain yield response in lentil to the application of MAP at landscape Position 3 (Table 2), with lentil having the highest yield in all treatments where 50kg/ha of MAP applied. The response to P inputs on this soil type was again predicted through soil tests collected prior to sowing, which recommended that 40–60kg MAP/ha was required to maximise lentil yield at this location. Pre-sowing soil testing showed that P responses were less likely on the other soil types. There was no significant benefit from the application of SOA or trace elements to lentils at the site in 2023.

Table 2: Effect of nutrition treatments on lentil grain yield (t/ha) across the six landscape positions.

Treatment

Landscape position (1 = swale, 6 = dune)

1

2

3

4

5

6

Nil

0.70

0.69

0.58

0.26

0.19

0.21

MAP 25kg/ha

0.65

0.76

0.61

0.28

0.19

0.21

MAP 50kg/ha

0.76

0.81

0.66

0.29

0.20

0.23

MAP 50kg/ha + SOA 50kg/ha

0.74

0.75

0.70

0.31

0.22

0.23

MAP 50kg/ha + SOA 50kg/ha + Trace Elements

0.78

0.75

0.66

0.28

0.20

0.20

P value

0.47

0.29

0.03

0.68

0.83

0.70

Lsd (p<0.05)

n.s.

n.s.

0.08

n.s.

n.s.

n.s.

Metribuzin tolerant lentils

GIA Thunder was 25% higher yielding than GIA Metro at Loxton in 2023. Where herbicide treatments were consistent across both varieties, the grain yield of GIA Thunder was 0.65t/ha, while the grain yield of GIA Metro was 0.49t/ha (Table 3).

The post-emergent application of 280g/ha of metribuzin did not affect the grain yield of GIA Metro. However, other herbicide treatments had a negative effect on the grain yield of GIA Metro, but not GIA Thunder. The IBS application of simazine and diuron reduced the grain yield of GIA Metro by 12%, relative to the nil treatment with no herbicide applied. The post-emergent application of Intercept also had a negative effect on the productivity of GIA Metro, with an 18% reduction in grain yield.

Rainfall during April provided for early emergence of broadleaf weeds, which were controlled with knockdown herbicides prior to sowing. Therefore, weed levels were low and did not affect grain yield. In situations where there are substantial weed burdens, the yield difference between the two varieties may be less when post-emergent applications of metribuzin can improve weed control.

Table 3: Grain yield (t/ha) for GIA Thunder and GIA Metro lentils with different herbicide treatments applied. Lsd (p<0.05) = 0.18t/ha.

Herbicide treatment

Variety

Group 5 Herbicide

Group 2 Herbicide

GIA Thunder

GIA Metro

Nil

Nil

0.67

0.59

Nil

Intercept (750mL/ha) PE

0.70

0.46

DP (IBS)

Nil

0.63

0.48

DP (IBS)

Intercept (750mL/ha) PE

0.61

0.45

DP (IBS)

Nil

N/A

0.59

DP (IBS)

Intercept (750mL/ha) PE

N/A

0.49

Conclusion

Deep ripping provides substantial yield benefits to pulse crops grown on sandy soils. In trials conducted near Loxton in 2022 and 2023, a yield increase of 30–80% was measured across two contrasting production seasons. However, deep ripping only benefited pulse production on the deep sandy soil on the dune, as there was no benefit of deep ripping the clay loam–loam soils located in the swale.

Lentils were responsive to high rates of phosphorus fertiliser supplied as MAP on some soil types. However, soil testing across both seasons identified low soil P levels at the locations where responses to MAP inputs were measured. At these trial sites, there was no significant benefit from the application of SOA or trace elements to lentils, while in chickpeas there was no benefit from any nutrition treatment, including from the application of MAP.

Dual metribuzin + imidazoline tolerant lentils are a promising management option for Mallee pulse growers to consider. At Loxton, the post-emergent application of 280 g/ha of Metribuzin to GIA Metro had no impact on grain yield. However, in a situation where weeds did not limit production, GIA Thunder, which only has imidazolinone tolerance, was 25% higher yielding than GIA Metro. In situations where there are substantial weed burdens, the yield difference between the two varieties may be less when post-emergent applications of metribuzin can improve weed control.

Acknowledgements

The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the authors would like to thank them for their continued support.

Contact details

Michael Moodie
7B Byrne Court, Mildura VIC 3500
0448 612 892
michael@frontierfarming.com.au
@Moodie_ag

GRDC Project Code: UOA2105-013RTX,