Although the cereal–oilseed crop–legume rotation offers advantages in terms of disease control, microbial abundance and nutrient transformation, there is little incentive for growers in southern cropping systems to increase plant diversity by growing alternative winter crops. This project aims to investigate other options to increase plant diversity, such as summer cover cropping, intercropping or companion cropping, and to examine their impacts on soil function and winter crop yields.

• During 2019, nine crop treatments were established using a range of winter crops (including wheat, field peas for grain and brown manure, as well as a brown-manure mix) at Burramine, Victoria, as part of a larger, long-term project looking at increased plant species diversity in cropping systems.
• A number of plots from this trial were sown to summer crop mixes during January 2020 and this impacted on water availability (when canola was sown over the treatment plots during May 2020) and levels of some diseases in the soil. During 2020, canola and peola were sown over the treatments established during 2019.
• The use of a pulse in the rotation, or inclusion of a brown-manure crop, substantially increased mineral nitrogen (N) at sowing of the subsequent canola crop.
• There was no difference in biomass production or yield between the control and the pulse rotation treatments or the control and increased diversity treatments.
• Cover crops sown during 2021 were affected by poor summer rainfall