Richard & Sharon Barrett

Deep ripping yellow sandplain to overcome compaction layer and optimising K rates according to production zones.

Paddock investigations revealed that:

• Yellow sandplain had a compacted layer 20cm below the soil surface.
• Yellow sandplain had a subsurface acidity problem with high aluminium levels.
• Parts of the paddock were limited by soil potash levels.

Two trials were designed to test the economics of ameliorating these constraints to production within each productivity zone.

• Deep ripping
• Potash application

• The deep ripping trial was ripped pre seeing to a depth of 45cm. There were 4 replications in the trial with control plots between the ripping plots.
• Calingiri wheat was sown on the 19th of June.

• Muriate of potash was spread post seeding at rates of 0, 70 and 120kg/Ha.
• The soil contained between 40 and 50ppm of potassium.

• The deep ripped plots (2.15T/Ha) yielded 28% more than the control plots (1.68T/Ha).

• This resulted in an increased return of $138/Ha.
• After the cost of ripping, an additional $100/ha was generated
•  The ripping response is likely to be from a combination of:

- improved water use.

- access to accumulated nutrients deeper in the soil profile.

- mineralisation of nitrogen due to the cultivation effect.

• There was little difference in grain quality between ripped and control plots.

This site will be monitored during 2003 to investigate the benefits to the following canola crop.

Applying 70kg/Ha was adequate to alleviate the MOP deficiency. Increasing MOP rate to 120kg/Ha did not economically increase grain yield.

The gross return per Ha after paying for and applying the potash was: 

$376 - 70kg MOP

$368 - 120kg MOP

$334 - O MOP

• Deep ripping to overcome subsoil compaction is extremely profitable even in a dry year.
• In a low yielding season (1.2-1.5T/Ha) applying potassium to soils with 40-50ppm an economical yield response ($42/Ha).