Soil constraints that limit wheat yield in south-west Western Australia

Page last updated: Monday, 18 October 2021 - 9:09am

Please note: This content may be out of date and is currently under review.

Large areas of cropping land in Western Australia have soil with multiple constraints to crop yield. Treating one constraint, when there are several interacting constraints, may not give significant and profitable yield benefits. The Department of Primary Industries and Regional Development analysed existing regional-scale soil-landscape mapping to identify land where treating a single constraint is likely to result in a significant yield response.

The message

There are profitable treatments for many areas affected by 1 or 2 soil constraints to wheat production.

What we did

This analysis was developed from our land capability, most-limiting factor tables. It builds on earlier work that reported wheat yield constraints at a local government scale in an attempt to identify where investing in management of soil constraints is likely to be profitable. In this analysis, we included 17 known soil constraints that limit crop production.

The steps in the analysis were:

  1. create a productivity map
  2. identify duplex soils on productive land only
  3. group similar production constraints within the database
  4. prepare summaries of constraints for every land unit within each map unit
  5. summarise land units that have few (1–3) constraints, where amelioration is likely to result in significant yield increases.

What we found

Based on regional-scale information, the analysis estimated that:

  • most of the wheat-growing land in south-west WA has one or more soil constraints
  • about 1.6 million hectares (9% of the total area) are not suitable for cropping
  • about 2.2 million hectares (12% of the total area) are suitable for cropping but are subject to many (more than 3) constraints; soil amelioration is unlikely to significantly improve profitable yield gain
  • susceptibility of subsurface acidity extends over 12.6 million hectares (about 70% of the total area); about 7.6 million hectares of that area (42% of the total area) is estimated to have only 1 or 2 soil constraints, and treating the most-limiting constraint is likely to achieve a profitable yield gain
  • susceptibility of subsurface compaction extends over 13.2 million hectares (about 73% of the total area); about 5.7 million hectares of that area (about 32% of the total area) is estimated to have only 1 or 2 soil constraints, and treating the most-limiting constraint is likely to achieve a a profitable yield gain
  • water repellence, surface salinity, subsoil alkalinity, low soil water storage, topsoil acidity and physical crop-rooting depth each restrict yield over at least 1 million hectares.

What this means

There is potential for profitable yield increases from treating land where there are only 1 or 2 soil constraints to crop yield. More than half of the agricultural area fits into this category.

Land-use planners, local government, and landcare and grower groups can use this information at the local, regional and state scale to estimate where research, development and extension activities are likely to have the largest industry impact. The same procedure – assessing the soil constraints on a given area – can be used by farmers and other land managers to set priorities for soil constraint amelioration.

Acknowledgement

The data analysis and yield modelling in this report were undertaken for the Grains Research and Development Corporation and the Department of Agriculture and Food, Western Australia project: Subsoil constraints – understanding and management.

For more information

Download Identifying soil constraints that limit wheat yield in the south-west of Western Australia – RMTR 399 (PDF 5.7MB)

Contact information

Dennis van Gool
+61 (0)8 9368 3899