Controlled traffic farming (CTF) improved soil structure and increased crop yields compared to conventional wheel traffic (C) methods on a Red Chromosol soil in South Australia over 6 years. Yields were 12-22% greater with CTF in 5 of the 6 years. Deep ripping had no effect on yields. CTF resulted in better soil structure with increased stable soil aggregates over 2mm and greater water infiltration rates compared to C. CTF also showed signs of improved root growth but the impacts on root morphology and response to diseases or stresses were not fully explained. The results were similar to those found on a Black Vertosol, indicating the benefits of CTF can apply across soil types.

1. Soil and yield improvements from Controlled Traffic
Farming on a Red Chromosol were similar to CTF on
a swelling Black Vertosol.
Tim Ellis
CSIRO, Brisbane (previously University of Adelaide)
Soroush Sedaghatpour, Cliff Hignett, Hugh Cameron, John Thomas, Jeff
Tullberg, Terry Riley and 1 x 106 students

2. Controlled Traffic field research conducted at
Roseworthy South Australia, 1989 to 1994
Funded by: Key Centre for Dryland Agriculture and
Landuse Systems; John Shearer LTD; Grains Research
Council; and Grains Research and Development
Corporation
Site - Roseworthy South Australia
Climate - Mediterranean-type– rainfall 440 mm/yr
Soil – generally Red Chromosol – some variation

3. Aim: shattering of compact layer and exclusion of wheel
traffic
(expectation): this should improve soil structure, root growth and crop yield
C – Conventional wheel traffic; tractors and trailed
implements
CR – Conventional wheel traffic, deep Ripped
CT – Controlled Traffic
CTR – Controlled Traffic deep Ripped
Ripping – 300 mm deep, once only at establishment of trial
Randomised split-plot design; each plot 0.1 hectares

4. A “moderate” compact layer
below tilled depth
Some root deflection

5. Controlled Traffic treatments CT and CTR
Tillage, seeding (DD) and Harvesting
spraying
Modified MF585 harvester
Experimental John Shearer
Gantry

6. Conventionally wheeled treatments C and CR
(just imagine)
Tractor(s) and (identical) trailed implements and
harvester

7. NS
• 12 to 22% greater yields from CT in 5 out of 6 years.
• No significant difference from deep ripping (surprise)

8. C Wheat
CT
“Better” soil structure if you don’t drive on it.
(seems obvious) Why?

9. C CT
CR CTR
Which structure is “better”? Deep ripping doesn’t necessarily “improve” soil
structure, especially if you don’t stop driving on it. Why?

11. Visible porosity (%)
1.6 0 5 10 15 20
Bulk density (gcm-3)
1.5 0
1.4 2
1.3 Depth (cm) 4
C tilled layer
1.2 CT tilled layer 6 C
1.1 C below tilled layer
8 CT
CT below tilled layer
1
10
1991 1992 1993 1994

12. C CT
Did CT reduce root
disease? Why?
Faster growth?
What type of root growth is “better”?

13. Soil penetration resistance

14. Barley
Soil blocks and
pinboards
Bean

15. Was this reflected in yields/morphology?
Why?

16. 100 100
Rainfall
Cummulative %
infiltration (mm)
80 CT 1994
80
Cummulative
C 1994
Infiltration C
60 60
CT 1992 Infiltration CT
C 1992
40 40
20 20
0 0
0 0.5 1 1.5 2 0 10 20 30
Aggregate size (mm) Time (min)
More stable aggregates > 2mm Greater infiltration

17. Conclusions/questions
•Simply removing the wheel traffic (CT) improved yields by
12 to 22%
•Deep ripping did not improve yields
•“Better” soil structure from CT – why? What at the
physical and ecological processes?
•“Better root growth from CT – but what is “better”?
•More stable soil aggregates; better infiltration
•Similar results to a swelling Black Vertosol
Bonus conclusions/questions
•Twice as many earthworms in CT compared to C
•Easier overall field operations and timeliness
•Improved efficacy of direct drilling
•Need to measure effects at system scale?

18. Thank you
Beans and concrete