Initial results from amelioration of gravel soils at Dandaragan trial site

Aug 06,2024 Project Update Article, Soil Amelioration Project, 2024, Projects, RAD2406,

By Kate Parker, WMG Project Officer

The GRDC funded Soil Amelioration Project aims to explore key aspects of soil amelioration on variable soil types including:

Diagnosing paddock scale soil constraints.
Identifying the most appropriate amelioration method(s) for the constraints.
Determining the economic advantage (ROI for the paddock) behind these methods.

Established in June, the Dandaragan trial site’s main focus is on dealing with soil water repellence and determining the most appropriate method of amelioration for the gravel soils present. The soil amelioration treatments include a control strip, Plozza plow, novel deep ripper (‘Fanger plow’), Nufab rip/delve, and a double pass of the Nufab rip/delve.

**Figure 1.** Trial design for the Dandaragan gravel soil amelioration site.

Early Results

Soil Testing

Soil tests were conducted pre and post amelioration for each of the treatments. Initial tests indicated a soil water repellency (MED) score of 2 in the top 10cm and a pH level of 4.6 throughout the profile. This sites soil type is shallow sand atop gravel as indicated by a 0% gravel proportion in the top 10cm and a 60-65% gravel proportion in 10-30cm.

Post treatment and post-rain soil tests indicated a slight rise in pH, particularly in the top 10cm as expected from an application of lime earlier in the season. Gravel re-distribution throughout the profile was evident in the treated strips versus the control with the Nufab double pass treatment having the largest mixing effect on the different layers within the soil. This was also true for various nutrients and organic carbon percentages.

Plant Establishment

There was no significant differences across the treatments for plant establishment however a trend was observed that the Fanger treatment had the most uniform establishment.

In general, all treatments had higher levels of establishment than the control strip.

In field observations noted high numbers of weeds in the control strip in comparison to almost zero in ameliorated strips, weed counts will be conducted later in the season post-weed treatment to ascertain how the treatments and control perform under traditional farmer practice scenarios.

There will be a pop-up crop walk at the Dandaragan site on Wednesday, 7th August from 3:00pm for those interested in a first look and to begin the initial establishment of a soil amelioration farmer discussion group. See the flyer below for more details.