Case study: Serradella and biserrula in the eastern Wheatbelt
Craig and Anna-Lisa Newman, "Karradale", Lake Grace
Background
Craig and Anna-Lisa Newman run a mixed cropping and sheep enterprise on 9000ha in the shire of Lake Grace. On average they crop 65% of the farm and run sheep on 35%, most of which have established regenerating pastures. The sheep business consists of 5000 head MPM (Multi-Purpose Merinos) which are self-replacing; the surplus ewes are sold or feedlotted pending on the market, and wether lambs are finished in the feedlot and sold as prime lamb. The cropping program includes barley, oats and some wheat along with serradella and biserrula seed crops.
Getting started in serradella and biserrula – how and why
In 2013 during a strategic planning meeting, the Newmans identified a major flaw in their pasture systems: they were almost non-existent. Cropping paddocks in a ‘break year’ were only growing volunteer cereals and broadleaf weeds/ryegrass as the main feed source for the sheep. Sub-clovers and medics were patchy and inconsistent depending on the break of the season. Any greenery needed to be desiccated by September/October to prepare the paddock to return to crop in the following season, but the result was a feed gap until crop stubbles were available after harvest. The Newmans felt that they could overcome the feed gap to create benefits for the livestock enterprise, but also for the subsequent cropping year. Around this time, the Newmans also purchased a run-down property with areas of acidic gravels and deep sands.
In 2014, whilst actively looking for different options, the Newmans heard about serradella at a Regional Crop Update. They were drawn to some key characteristics of the pasture species: the robust nature of the seed to false breaks, the nutritional composition (high protein source), the biomass traits per mm of rainfall (more than clovers), the yield potential and harvesting ease. The ability to utilise the summer sowing window as a method of establishment was a realistic way to achieve their ambitious goal of establishing 6400ha of pastures in 5 years. High summer temperatures break down the hard-seed of French serradella to provide a seed bank ready to germinate at the break of the season. The Newmans kept in close contact with Dr Angelo Loi, DPIRD pasture specialist, during the early integration of the system to ensure that they followed the ‘Golden Rules’ and had success in every season.
Establishment and management: ‘The Golden Rules’
Management of the pasture in the first year required close attention to stocking rates, ensuring that pastures are well established, grazed to a careful level then stock removed by August. This was particularly important in a low rainfall zone to ensure enough biomass to either set a good seedbank or achieve seedbank plus harvest.
Anna-Lisa Newman advised that Angelo Loi’s summer sowing golden rules must be followed! These include:
- Select paddocks with low weed content (after single or multiple non-leguminous crops) and where the use of sulfonyl-urea based herbicides (group B) or clopyralid (group I) has been avoided.
- Use un-scarified hard seed or pods (germinability 5-10%) drilled into the soil at approximately 1cm deep.
- Sowing time is critical and should start as early as possible after the crop has been harvested and sown no later than early March.
- Sowing rates should range between 15-30kg/ha of pods of hard seed French serradella
- Inoculation must be carried out with dry granules. Inoculation may not be required for serradella in paddocks with a recent history of lupin production (including blue lupin pastures).
- Crop stubble should be minimised as much as possible prior to sowing to expose seed or pods to the high summer temperatures.
- Apply appropriate fertiliser at sowing depending on soil test results and recommendations.
- In the first year of establishment, red-legged earth mites need to be monitored and controlled as necessary.
- Apply a suitable grass selective herbicide as post-sowing pre-emergence or in mid to late winter.
- Winter grazing and/or manipulation with a broadleaf herbicide (Imazethapyr or Imazamox for serradella) may be essential for weed suppression.
- It is often recommended an application of Imazethapyr as a pre-emergence treatment before the break of the season.
The management strategies are no different to another legume crop like peas. The Newman’s mindset had to shift from “just a pasture” to treating it “like a crop” – which resulted in successful establishment and better management.
Benefits
The Newmans are now seeing the benefits of serradella and biserulla pastures flow into both their sheep and cropping enterprises. Ewes are maintained in good body condition, often due to the presence of green feed for up to 10 months of the year. Lambing rates have increased to 100% for the last three consecutive years and wool production has risen in kg/hd. Soil benefits include the accumulation of soil nitrogen; the Newmans are now testing this theory by growing high yielding crops without further nitrogen being applied.
Serradella and biserrula are hardy plant species. Biserrula is the ultimate survivor of early January/February rain and is able to hold on until further rain events in autumn. Both species have a tap root system which utilises water from lower in the profile, but biserrula is much more tolerant of heavy soil types and excels in much tougher conditions. Early season rainfall can be utilised and creates invaluable early feed in pasture paddocks. Additionally, the biserrula is competitive with weeds in an early break.
Both plant species can produce high amounts of biomass relative to rainfall, which is beneficial for both livestock and cropping systems. Increased biomass contributes to overall soil health, nitrogen levels and gives ground cover, which reduces erosion risk and creates a mulch layer on the soil to help mitigate summer temperatures. Serradella and biserrula in crop is palatable and nutritious however sheep will preferentially graze other weeds first which is advantageous. The Newmans manipulate the pastures for grasses usually once; however, when there is intense early competition and high weed numbers they use a two-spray strategy, similar to how a pea or lupin break crop would be used to manage grasses in crop.
Problems and learning opportunities
Pre-emergent broadleaf weed control is important; the Newmans have been caught out with late germinating radish on some of their newer farms, however the use of a weed-wiper has overcome the problem successfully.
Other problems include identifying and managing soil type variations in large paddocks – the Newmans have started sowing smaller patches to biserrula to replace serradella, and they have experienced other typical cropping-related problems such as blocked air-seeders, sowing too deep, missing aphid infestations (on biserrula) and minor Budworm damage (spraying too late).
Craig and Anna-Lisa are conscious of the risk of photosensitivity with any high protein pasture source but are not convinced that the condition should be only associated with biserrula. They have seen a small number of lambs with severe photosensitisation, but numbers have always been less than 1% of the flock. In most seasons they find that pasture germination often coincides with volunteer cereal regrowth (and other weeds) which provides carbohydrates and gives some balance to the high protein levels in the legumes. They offer hay during the autumn feed gap if needed and barley grain in lick feeders and have not seen any severe issues in their ewes to date.
Future plans
The Newmans plan to continue monitoring the legumes in the system and are looking to understand the interplay of nitrogen and potassium to ensure soil and crop nutrition are optimised. Anna-Lisa is particularly looking forward to seeing the full potential of these pasture species when an above average rainfall season occurs. At that time, they plan to capitalise on the opportunity and make hay or silage, and/or top up silos with pod and seed (which can store for many years).
They may also consider adding other serradella species with different strengths and characteristics into this base system, but for now they are focusing on learning how to manage the overall system better.
Further information is available on serradella and biserrula.
Acknowledgement
Some of the work conducted by DPIRD at the Newman's farm was funded by the Dryland Pasture Legume Systems project.