Take Home Messages
- Two new barrel medic varieties, Penfield and Emperor, and the balansa clover variety, Enduromax, are performing well in the southern Mallee.
- Sown cereal pastures can be supplemented with additional protein through undersown legume pasture, legume hay or grain to meet the requirements for high livestock production.
- Greater diversity in sown pasture mixes provides nutritious feed at different times during the season and benefits soil health
Aim
To demonstrate the production and grazing value of new and existing legume pasture options sown alone or in pasture mixes with cereals, and the effect of fertiliser on performance.
Background
Regenerating legume pastures have declined during recent periods of drought, as cropping rotations have intensified, and improvements in genetics and agronomy have brought better success growing grain legumes. But not all paddocks or seasons are suitable for growing grain legumes and their presence is still low in rotations, increasing reliance on fertiliser nitrogen. There is clear evidence that without pasture rotations that can fix soil nitrogen (N) and help to re-build soil carbon, organic matter levels are steadily declining (Reeves, 2020).
Recent National Landcare Program (NLP) funded ‘Grazing Standing Crops’ projects have demonstrated the value of growing a cereal crop that is held as a fodder bank to be used later in the year for lambing and weaning lambs onto, or to finish lambs between three and six months of age. The standing crops are grazed from late stem elongationto grain fill, and can be a combination of a cereal with a pasture legume or grain supplement to supply higher quality protein feed needed for fast-growing lambs.
In 2022, new release medic varieties demonstrated improved performance and valuable feed quality. By mid-October, the new release medics produced 2t/ha more biomass than older medic varieties and recorded 4–10 per cent higher digestibility and 10 per cent more protein than cereals sown for fodder at that time of year (Frischke, 2023). The 2022 season had an exceptionally wet spring, and the new release medics needed field testing in another season.
Paddock Details
Location: Kinnabulla
Crop year rainfall (Nov–Oct): 276mm (decile 3)
GSR (Apr–Oct): 187mm (decile 3)
Soil type: Sandy clay loam
Paddock history: Lentil brown manure
Trial Details
Crop type/s: Medic, clover, vetch, barley, forage radish
Treatments: Refer to Table 1
Seeding equipment: Knife points, press wheels, 30cm row spacing
Sowing date: 2 June 2023
Trial Inputs
Fertiliser: Granulock Supreme Z + Flutriafol (400mL/100 kg) @ 60kg/ha at sowing
The demonstration was hand weeded and managed as per best practice for insects
Method
Single plots of legume pastures medic, clover and vetch, and mixes with barley and forage radish were sown as a demonstration. Peak biomass was measured, and feed tests conducted on a selection of pastures.
Results & Interpretation
Measured in late March from 0–120cm deep, plant available water was 157mm and soil nitrogen was 254kg/ha. Soil organic matter was 1 per cent.
The 2023 growing season at Kinnabulla began after opening rains of 37mm fell in the third week of April, joining surface moisture with deep moisture from the exceptionally wet spring in 2022. Conditions then turned dry until the third week of May when 11mm of rain was recorded. The trial was sown ahead of 24mm in the first week of June and established evenly. Growing season rainfall ended on a decile 3 and although conditions became dry at times, the combination of conserved soil moisture and just enough rain falling at critical times produced good biomass production and crop yields.
Biomass value
Peak biomass sampled on 15 September, when all pastures were flowering, measured 1.5–2.5t/ha for medics and clover, 1.5–2.8t/ha for vetches, 7.3–14.3t/ha for barley, and pasture mixes were 4.4–12.0t/ha, noting that plots were unreplicated (Table 1).
New medic varieties, Penfield and Emperor, were better able to use late August rains than the older variety, Cavalier. Penfield and Emperor produced the most biomass (>2t/ha) in the absence of powdery mildew, repeating results seen at Nullawil in 2022.
Enduromax clover grew similar biomass to Seraph medic, as did the high density legume (HDL) pasture blend.
In this demonstration, vetch performed lower than expected (biomass yields of vetch sown at the end of April at the Kinnabulla pulse trial site measured 3–6t/ha). Timok grew the most biomass which was 1.1t/ha more than the lowest biomass variety, Studenica.
Although not measured, it is unlikely the legumes would have nodulated and fixed soil nitrogen in 2023 given the high starting soil nitrogen resulting from nitrogen mineralisation after the exceptional 2022 spring and favourable 2023 season break conditions.
Grain barley variety, RGT Planet grew exceptional amounts of biomass, producing twice as much as forage barley Kraken by mid-September. However, in practice, Kraken should be grazed once or twice during the season before being locked up. It responds well to early grazing to promote its tillering characteristic and will grow back with greater bulk than if left ungrazed. Kraken had slightly better quality than RGT Planet barley (Table 2) and being an awnless variety offers better ‘mouth-feel’ for grazing livestock.
As expected, the total biomass of pasture mixes including cereals were lower than the cereal growing alone.
Nutrient value
Digestibility ranged from 65.4–73.1 per cent, which is suitable for moderate livestock production rates. Generally, pure legume or legume mixes had higher digestibility than cereals alone in September.
Crude protein was also highest for legume pastures exceeding 20 per cent protein, as well as the RGT Planet/Morava blend. Several blends raised the protein content higher than cereals alone. All pastures were testing >9.5MJ ME/kg DM at flowering – providing useful levels of energy for maintenance of dry ewes, ewes in early pregnancy or young lambs, but not for production feeding. Pastures testing above 10.8MJ ME/kg DM would support fast-growing lambs.
Acid detergent fibre (ADF) and neutral detergent fibre (NDF) levels were increasing, but still met targets used for high quality hay of ADF <30–32 per cent and NDF <55 per cent.
Fertiliser effect
Two plots of several pastures were sown, both with and without fertiliser. As occurred in 2022, there was a useful fertiliser response in biomass (Table 3).
Commercial Practice and On Farm Profitability
Two new barrel medic varieties, Penfield and Emperor, performed well again in a season with several dry periods. Barrel medics are well suited to the Mallee as they are adapted to a wide range of soil types and are the most drought and grazing tolerant of the medics.
New variety, Enduromax clover grew similar biomass to Seraph medic, showing potential as a new balansa clover option for low to medium rainfall areas.
It is likely that the medic and clover varieties would have continued to grow and use rains that fell after mid-September had they kept growing.
Establishment of a mix of hard-seeded varieties with a diverse suite of traits, for example plant maturity, SU tolerance, insect and powdery mildew resistance, will improve a pasture’s ability to regenerate and persist.
Growing mixes of legumes with cereals and brassicas supplies valuable feed at different times during the growing season (Frischke, 2023). In mixes, legumes and brassicas compete with the cereal, producing lower biomass than cereal alone, but higher biomass than either legumes or the brassica alone. Sheep will tend to eat cereals first, then the brassica and legumes later in spring, as plants grow through the season. Feed testing will identify nutrient deficiencies and guide whether supplements are needed to support production of different livestock classes.
Although changes to soil health weren’t measured in this demonstration, pasture mixes with legumes will help to build soil nitrogen, and reduce soil and plant-borne disease loads with lower densities of each species. Nitrogen fixed under vetch treatments and changes to plant available soil nitrogen at sowing is being measured at the Kinnabulla pulse site in the GRDC ‘Vetch end use and how it affects the cropping rotation’ project (see page 171).
References
Frischke A., 2023, 2022 BCG Season Research Results, ‘Managing standing crops for production, livestock nutrition and soil cover’ pp 124–130, <https://www.bcg.org.au/research-article/managing-standing-crops-for-production-livestock-nutrition-and-soil-cover-2022/>.
Reeves, T., 2020, GRDC Update Papers, ‘Is sustainable intensification of cropping systems achievable?’, <https://grdc.com.au/resources-and-publications/grdc-update-papers/tab-content/grdc-update-papers/2020/02/is-sustainable-intensification-of-cropping-systems-achievable>
Acknowledgements
This demonstration was supported by the Australian Government Future Drought Fund – Drought Resilience Adoption and Innovation Drought Hub, North-West node. Special thanks to Millie Moore of S&W Seed Company for providing pasture seed.
