The impact on crop performance from trafficking in low rainfall zones has been found to be far less dramatic than in those of different soil types and climates.
The interim results come two years into a five-year research project, funded by the Grains Research and Development Corporation, called ‘Application of controlled traffic farming (CTF) in the low rainfall zone’.
The project’s four research sites (in Victoria, South Australia and NSW) show an impact on crop performance from trafficking on the soil, with a five to 30 per cent difference measured in severe traffic conditions.
At this point in the project the differences measured are not as large or as constant as found in the self-mulching clays of Queensland or the sandy soils of Western Australia.
The question now for researchers is, why? It is hoped this will be answered from two more years of measurements off the research sites and through activities to be undertaken by the five farmer groups who are partners of the project.
During the 2015 and 2016 seasons the Farming System Group Partners undertook various activities connected to CTF, such as the investigation of the effect of wheel tracks on crop yield in farmer paddocks of three of the FSGP in 2016.
Crop cuts on and off wheel tracks were taken just before harvest, weighed and the results indicated that in the majority of cases yields were higher in non-trafficked areas compared to on wheel tracks. However, this was not always the case, raising the questions:
■Are the yield differences a result of wheel crushing of plants or is it the compaction effect?
■Why are some yields on wheel track better than off wheel track?
It is hoped the FSGP will be able to undertake sampling again this season.
A paddock near Swan Hill was included, as part of a project ‘CTF Effects on Soil Emissions’, to collect data on greenhouse gas emissions and denitrification loss.
The data showed that trafficked areas in a barley crop lost twice the amount of greenhouse gas emissions (690kg/ha carbon dioxide equivalent) and denitrification loss (more than 25kg/ha N) than the non-wheeled areas.
Emissions are highly variable, so we can be more confident of the ratio of losses from beds and wheeled soil than the absolute values, but they are in reasonable alignment with other tests in Victoria.