Soil compaction is a hidden and continuing constraint to cotton productivity due to increasing size and weight of equipment and is estimated to be in the order of >$30M in lost revenue. Growers recognise compaction is an issue and address this by adopting pseudo-controlled traffic farming systems, however the incompatibility of equipment used by different crops restrict options for a fully matched CTF system. Identifying the extent of compaction is problematic: penetrometers measure soil strength which is dependent on soil moisture making interpretation difficult.

The project will engage with the cotton industry using discussion around soil pits in each cotton region to determine the extent of soil compaction as a constraint or cost to productivity with respect to water, nitrogen and energy use efficiency and subsequent yield and fibre quality. A recent survey of a limited number of growers suggested that 35 % of growers need to be able better identify soil compaction and have access to new strategies to “avoid” compaction, while the remaining 65 % would like novel strategies to ameliorate compaction and understand which strategies were more effective than others. These results indicate that the cotton industry appreciates that soil compaction is an issue and are looking for strategies to minimise the effect in the first instance and to determine which remediation practices are the most effective.

Soil compaction is seen as a negative in farming systems, perhaps we need to reassess the issue. Agricultural industries need to utilise soil compaction for benefit; as in a fully matched controlled traffic farming (CTF). Soil compaction is a constraint to productivity when it is allowed to occur in a random fashion, for example a non CTF system. This enables soil between traffic lanes to be managed optimally for water and nutrients and for crop growth. There is opportunity to manage or minimise the effect of soil compaction in cotton systems as growers tend to be land “rich”, providing an opportunity to ameliorate the effect of a wet pick by increasing the time between cotton in any one area.

The project plans to determine how growers currently identify soil compaction and the extent of the problem and to identify current strategies for minimising compaction in the first instance and then determine what growers are implementing to ameliorate/mitigate the effect of compaction. A key component in this is, how do growers decide which strategy to adopt and what is the criteria of success or otherwise of the outcome? By minimising compaction in the first instance the necessity for amelioration is minimised, which will reduce the cost of production. This should translate into greater water and fertiliser use efficiency and less greenhouse gas emissions. The industry will be able to optimise resource use to maximise productivity per ML of limited water. A key component of the project will be understanding how soil constraints are prioritised within the farming and management system.