RiskWi$e Spring Cover Crop

Use of Spring-Sown Leguminous Cover Crops to Increase Available N

Key Messages

Investigating if spring-sown cover crops can mitigate on-farm nitrogen decision risks.
Seek to better understand the potential benefits of spring cover crops on soil health and the following cereal crop.
Confirm if spring cover crops are appropriate crop rotation for the Wickepin & local growing region.

Project Aim:

The Spring Cover Crop Project is a part of RiskWi$e, a National Risk Management Initiative. It is a 5-year initiative by GRDC and CSIRO that will run from 2023 to 2028. It seeks to understand and improve the risk-reward outcomes for Australian Grain Growers by supporting grower on-farm decision-making.

The cost of inputs, including nitrogen has increased. Finding alternative nitrogen sources, including those from legumes, is a key management choice that could reduce on-farm nitrogen decision risks. However, most legumes are sown over winter, and replace a cereal cash crop within the cropping system rotation.

The aim of this project is to investigate if spring-sown leguminous summer crops will result in higher winter crop yields and improved soil N compared to a fallow period over summer in the Wickepin area. This trial will provide our members with further understanding of how summer cover crops can benefit soil health and function and what the consequences may be for the growth and yields of subsequent winter crops.

Project Background:

Spring cover crops have been found to have positive effects on soil health including increasing organic carbon, reducing soil erosion, enhancing microbial activity and diversity, and mitigating nitrate leaching during fallow periods (McNee, 2022; Zhang et al., 2023). Spring and summer-sown cover crops are often found in parts of Australia that have a tropical climate with moderate to high summer rainfall due to most cover crop varieties favouring warm wet conditions.

Western Australia has a Mediterranean climate known for its cold, wet winters, and hot, dry summers. Out-of-season rainfall between November and March has increased in the medium to low-rainfall areas within the Wheatbelt of Western Australia (Scanlon & Doncon, 2020). While research in spring cover crops is extensive there is little research to quantify the benefits in Mediterranean climates similar to those found in Western Australia (McNee, 2022).

To fill this knowledge gap, the Facey Group undertook a 1-year project with Soil CRC whereby various legume and non-leguminous cover crops were sown in favourable conditions in the spring of 2021. There was minimal rainfall over the summer period, however, in April 2022, multiple species survived and continued to grow and produce biomass. In 2022 the winter crop was assessed for various soil parameters and crop yield. Initial results demonstrated that the spring-sown cover crops did not impact subsequent crop yield. The project also found an elevated soil N available at seeding in the plots that grew leguminous cover crops.