WAARC: Innovative management approaches to maximise the use of legume crops in redirecting the reliance on fertiliser N in WA cropping systems

Key Messages

  • Supplying sufficient and timely nitrogen is key to ensuring high crop productivity, yields and grain protein levels. This new project is led by the WA Agricultural Research Collaboration (WAARC) with co-investment from GRDC.

PROJECT BACKGROUND

Overall, the N-ABLE Project will investigate biological nitrogen fixation from legumes through numerous field studies that include legume companion cropping and summer active legumes.

 The Stirlings to Coast Farmers component of the project is two-fold and will:

  • Pilot the effectiveness of a summer legume cover crop in the HRZ of the Albany port zone, in place of a summer chemical fallow, to supply following winter grain crops with residual soil nitrogen that will justify cutting nitrogen fertiliser rates without compromising productivity outcomes.
  • Pilot the effectiveness of seeding a hard-seeded legume with a winter cereal with the theory that the hard-seeded legume will germinate later in the growing season (September – October) causing minimal impact to the winter cereal crop, but then going on to produce nitrogen over the summer for the following winter crop.

METHOD

Summer Active Legumes

In the summers of 2023/24, one small plot trial site will be established with at least 6 summer treatments this will include summer active legume species, and non-legume (Millet) and chemical fallow controls with three replications. In the winter of 2024 and 2025, a cereal crop will be established over these plots with at least two rates of fertiliser N. Irrigation will be organised if sufficient rainfall is not received to allow sowing. The small plot treatments will include:

  • Faba Bean
  • Soybean
  • Lablab
  • Pigeon Pea
  • Field Pea
  • Pearl Millet
  • Chemical Fallow (farmer practice control)

 The treatments will be seeded, inoculated and managed in line with best practice agronomy for each species selected with the aim of maximising biomass production and nitrogen fixation. The treatments will be laid out in a randomised complete block design with three replicates to minimise spatial and environmental error and ensure a robust data set can be collected.

Each species will be terminated at either of the following: peak biomass (early to mid-flowering), prior to seed set, or at the time of the autumn knockdown spray if the previous two criteria are yet to be met. Termination will be conducted on an individual species basis, as each species will differ in growth rates, growth stage triggers, and seasonal response. The species will be monitored by SCF for growth stages and terminated (by chemical spray) by SCF.

Each year the following measurements will be completed to better understand the contribution of nitrogen (N) from the legume CC to the following winter cereal crops (to develop a comprehensive N budget).

  • Full trial site soil characterisation (one core per treatment block), Predicta B, Soil tests to 30cm (prior to seeding each cover crop, prior to seeding each winter crop).
  • Deep N soil coring to at least 100cm, 3 soil intervals (prior to seeding each cover crop, prior to seeding each winter crop, at harvest of winter crop.  
  • Legume crop establishment measurements (2 weeks after seeding or rainfall event) and weed counts (prior to chemical termination).
  • Nodulation score/assessment (Prior to chemical termination).
  • legume biomass assessment and tissue and N15 test (prior to chemical termination).
  • winter crop tissue test H100.
  • winter crop harvest biomass and tissue test yield and grain protein
  • Drone Monitoring and data analysis – Biomass/NDVI and canopy cover – enhance results and provide an improved visual resource for extension of information to growers.

 

Acknowledgements

This project is led by the WA Agricultural Research Collaboration (WAARC) with
co-investment from GRDC.

To find out more

Reach out to project lead Anne Wilson;  anne.wilson@scfarmers.org.au