Boosting profit and reducing risk on mixed farms in low and medium rainfall areas with newly discovered legume pastures enabled by innovative management methods

Background

The uptake of new pasture legume varieties in the Victorian Mallee is currently low. Annual medic and vetch remain the dominant crop choices however, there are a range of new pasture varieties which have potential in low to medium rainfall environments. A number of these pasture legumes come from the Western Australian breeding program and have limited evaluation in the Mallee. They possess different maturities, growth habits and are generally suited to neutral to acidic soil types.

A significant obstacle to the adoption of new pastures legumes is the high cost of pasture seed and difficulty in establishment. A feature of some of the new pastures under investigation is their aerial seeded habit and retention of seed, allowing seed to be grower harvested and re-sown with standard cropping equipment. This is in comparison to traditional medic pastures which require costly vacuum harvesting equipment.

The majority of medic and vetch currently sown in the region is established in autumn. A number of the new pasture legumes contain hard seed characteristics that provides a viable pasture after many cropping phases. The capacity to employ alternative establishment methods such as twin (sown with crop before the pasture phase) and summer sowing has been a particularly effective strategy across regions of NSW and Western Australia under a range of growing conditions including extreme drought (Nutt et al. 2021). Hard seeded pasture legumes offer capacity to develop flexible crop-pasture rotation systems that exploit this characteristic. Summer sowing was developed to utilise the opportunity of being able to header harvest pasture legume seed easily on farm and then successfully establish a pasture without needing to further process the seed. This project is examining the potential of different pasture legume species to be established more efficiently, reduce establishment costs and improve productivity from greater water use efficiency.

Aims

The Dryland Legumes Pasture Systems (DLPS) project was undertaken to improve the quality of annual pastures on mixed farms receiving less than 450 mm annual rainfall in Western Australia, South Australia, Victoria and New South Wales. A multi-season trial was established at Piangil, Victoria and aimed to;

  1. Aid growers with the selection of new pastures in comparison to traditional medic and vetch crops
  2. Improve pasture establishment using novel sowing strategies
  3. Assess seedbank regeneration of new pasture legumes
  4. Evaluate the harvestability of pastures using standard harvesting equipment
  5. Quantify the farming system benefits of regenerating legume pasture systems

Method

A replicated trial was established at Piangil from 2018 to 2021. The trial included 3 main plots (establishment method) x 7 subplots (pasture variety) x 4 replicates. The three establishment methods were used;

  • Twin-sown, where ‘hard’ pasture seed/pod was sown with Compass barley seed on 28 June 2018 for pasture establishment in 2019
  • Summer-sown (7 February 2019), where ‘hard’ seed/pod was sown in summer and softens to establish on the autumn break
  • Autumn-sown (control treatment), where ‘soft’ germinable seed is sown on the break   (13 May 2019) of the season
Figure 1. Pasture establishment methods (Flohr et al. 2022).

Seven pasture species were evaluated in this trial, Annual Medic, Biserrula, Bladder clover, Gland clover, Rose clover, Serradella and Trigonella.

The seeding rate of the pasture legumes was calculated on the basis of providing each species and establishment method with 100 germinable seeds/m2 in autumn 2019 (Table 3). This took into account seed regeneration from twin sowing and ‘soft’ seed percentages. Any 2018 germination from the twin sowing which remained in 2019 was chemically removed. Two comparison treatments were also sown in 2019: Barley to represent a continuous cereal system and autumn sown vetch that was browned manured in spring.

In 2020 the entire trial was sown to Catapult wheat on 28 April by direct drilling into the existing pasture, barley and vetch plots. Basal fertiliser was applied as 62.5 kg/ha of DAP S Z with 43 kg/ha urea top dressed on all plots on 19 June 2020. All pasture species were allowed to regenerate in 2021.

Pasture species included in this trial

Results

2019 Pasture Establishment and Production

Twin and summer sowing strategies were useful tactics when compared to conventional autumn sowing for some varieties. For bladder clover, gland clover and rose clover similar establishment rates were achieved from either autumn or twin sowing. Interestingly summer sowing was best strategy for Serradella and Trigonella. Autumn sowing was the best timing for Biserrula and annual medic.

Several new pasture legumes produced similar dry matter compared to commonly grown annual medic under tough growing where the site received less than half its long-term seasonal rainfall. Rose clover and bladder clover dry matter production was comparable to annual medic (Table 2). Biserrula and Serradella produced the next highest dry matter followed by Trigonella and gland clover.  However, all regenerating pastures had lower production than the sown vetch treatment.  Vetch which was terminated in September, still produced 3.2 t/ha of biomass. Similarly, the continuous cereal treatment was highly productive in the first year and produced a grain yield of 2.8 t/ha.


Break effects in the 2020 Wheat Crop

2020 pre-sowing soil nitrogen (kg N/ha, 0-1 m) , wheat grain yield (t/ha) and protein content (%) in response to seven pasture legumes, vetch and wheat sown in autumn 2019 at Piangil, Victoria.

Soil available nitrogen at the beginning of 2020 was high for all pasture species. The continuous cereal treatment has the lowest soil available nitrogen at 22 kg N/ha, clearly showing the benefit of having break crops in the system. All other pasture treatments and vetch had soil available nitrogen levels which ranged between 102 and 116 kg N/ha. Wheat grain yield and protein results highlighted the longer-term benefits of pasture systems. The continuous cereal treatment had the lowest grain yield of 1.8 t/ha and 10.7% protein. This was expected due to the low starting soil nitrogen (22 kg N/ha) compared to all other treatments. For all pasture and vetch varieties there was little difference in grain yield ranging 2.6 – 2.8 t/ha.  Grain protein levels were consistent across the pasture and vetch treatments averaging 12.3%


Pasture regeneration 2021

Pasture regeneration was adequate (>200 plants/m2) for five of the seven pastures in year three. Rose clover, bladder clover, annual medic, biserrula and gland clover were all greater than 231 plants/m2. The lowest regeneration at Piangil was observed for Serradella and Trigonella. Seredella has shown a number of favourable characteristics across the first two seasons in terms of biomass production and benefits to the following wheat crop.

However, in year three its persistence through the cropping phase was low which would be a problem for growers who want to maintain a seedbank. Dry matter regeneration was highest for Biserrula and rose clover across four sampling dates).  At various sampling times other pastures were also high yielding, for example, in September annual medic dry matter was higher than the other pasture options. Later in the season bladder clover and Serradella maintained similar biomass compared to Biserulla and rose clover.


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Acknowledgements

This virtual field day has been developed as part of the Mallee Sustainable Farming (MSF) project:
“Facilitating enhanced knowledge sharing of Mallee sustainable farming practices”
This project is supported by the Mallee Catchment Management Authority with funding from the Australian Government.

This project was supported by funding from the Australian Government Department of Agriculture, Water & Environment as part of its Rural R&D for Profit program, the Grains Research and Development Corporation, Meat and Livestock Australia and Australian Wool Innovation. The research partners include the South Australian Research and Development Institute, Murdoch University, the Commonwealth Scientific and Industrial Research Organisation, the WA Department of Primary Industries and Regional Development, the NSW Department of Primary Industries and Charles Sturt University, as well as grower groups.

Demonstration of French Serradella on soils in the Mallee

Background

Local research projects have found that French Serradella has the potential to provide a fodder option on Mallee sandy soils where lupins are normally grown. The potential benefits that serradella in the Mallee include:
• Adaptation to deep infertile, coarse textured soils
• Deep rooting and produces an extended green feed period compared to most annual legumes
• Potential for seed collection and cleaning with on-farm equipment
• Tolerance to pH (4.0< pHCa <7.5)
• Good tolerance to redlegged earth mite and aphids
• Very palatable to stock and high nutritive value
• No major anti-nutritional properties

There is also potential for Serradella to be established using novel methods aimed at reducing the cost of pasture establishment and improving productivity from greater water use efficiency. The methods are:
• Twin sowing where hard seed/pod is sown with the crop before the pasture phase. Little or no pasture is expected to establish in the crop phase. Hard seed “softens” over the summer period and germinates to produce a viable pasture in the following autumn.
• Summer sowing is where hard seed/pod is sown in the summer prior to the pasture phase where the hard seed “softens” and germinate to produce a viable pasture in autumn.

Demonstration Sites

A one hectare French Serradella demonstrations site was dry sown on the 1st of March at Ouyen. This site was was sown to lupin in 2019 and cereal in 2020. Treatment strips were 100 m long and ran from the near peak of an east west sand dune to the neighbouring flat. The site was intersected into 3 zones described as hill, mid-slope and flat. A block of Volga vetch was sown alongside to provide a comparative assessment of current local practice. The 0-10 cm soil pH (CaCl2) was less than 7 only on the hill location at Ouyen, increasing to more than 8 on the flat.

There was no measurable rain from seeding in March until late May. Rainfall was approximately 100 mm for the period from the end of May through to the end of September. A further 60 mm in October/November resulted in a total GSR of near 160 mm at both sites.

Serradella produced an extra 1 to 1.5 tonne biomass than vetch on the hill while vetch produced an extra 1 to 1.5 tonne of biomass to serradella on the midslope and flat (Figure 1).

Figure 1 Total serradella and vetch biomass (tDM/ha) in the 3 soil zones, at 3 sampling times at Ouyen.

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Recommendations

The demonstration sites show that serradella could provide a dual purpose (hay, grain, grazing) alternative to vetch on neutral to acidic deep sandy Mallee soils. These soil types are where lupins are commonly grown. Serradella can also provide operational benefits over vetch such as summer sowing and lower seeding rates.

To successfully establish a French serradella phase pasture we recommend:

  • Sowing in February early March. The time of seeding is necessary to continue the rate of seed softening of the shallow sown seedpods.
  • Sowing on-farm produced seedpod at 5 to 20 kg/ha. The seeding rate is based on the small seedpod size (10 kg/ha = ~250 seedpods/m2).  A soft seeded cultivar such as Eliza requires sowing at 5 kg/ha while 20 kg/ha is required for a hard-seeded cultivar such as Margurita pod.
  • Serradella and lupin share the same rhizobia species for inoculation(Group G/S rhizobia).  A history of lupin in the paddock reduces the the risk of inadequate nodulation and the need for inoculation, particularly where summer sowing of pod is used to establish the pasture.
  • Chemical weed control options include post-seeding pre-emergent Spinnaker (not Simazine) and/or post-emergent Broadstrike and grass selective herbicides plus a spring insecticide for Heliothis control.

Acknowledgements

This virtual field day has been developed as part of the Mallee Sustainable Farming (MSF) project:
“Facilitating enhanced knowledge sharing of Mallee sustainable farming practices”
This project is supported by the Mallee Catchment Management Authority with funding from the Australian Government.

This project was supported by funding from the Australian Government Department of Agriculture, Water & Environment as part of its Rural R&D for Profit program, the Grains Research and Development Corporation, Meat and Livestock Australia and Australian Wool Innovation. The research partners include the South Australian Research and Development Institute, Murdoch University, the Commonwealth Scientific and Industrial Research Organisation, the WA Department of Primary Industries and Regional Development, the NSW Department of Primary Industries and Charles Sturt University, as well as grower groups.