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
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
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 implementsCR – Conventional wheel traffic, deep RippedCT – Controlled TrafficCTR – Controlled Traffic deep Ripped
Ripping – 300 mm deep, once only at establishment of trial
Randomised split-plot design; each plot 0.1 hectares
A “moderate” compact layer below tilled depthSome root deflection
Tillage, seeding (DD) and spraying
Experimental John Shearer Gantry
Harvesting
Modified MF585 harvester
Controlled Traffic treatments CT and CTR
Tractor(s) and (identical) trailed implements and harvester
Conventionally wheeled treatments C and CR
(just imagine)
• 12 to 22% greater yields from CT in 5 out of 6 years.• No significant difference from deep ripping (surprise)
NS
“Better” soil structure if you don’t drive on it. (seems obvious) Why?
C CTWheat
Which structure is “better”? Deep ripping doesn’t necessarily “improve” soil structure, especially if you don’t stop driving on it. Why?
C
CTRCR
CT
1
1.1
1.2
1.3
1.4
1.5
1.6
1991 1992 1993 1994
Bulk
den
sity
(gcm
-3)
C tilled layerCT tilled layerC below tilled layerCT below tilled layer
0
2
4
6
8
10
0 5 10 15 20
Dept
h (c
m)
Visible porosity (%)
C
CT
What type of root growth is “better”?
Did CT reduce root disease? Why?
Faster growth?
C CT
Soil penetration resistance
Soil blocks and pinboards
Barley
Bean
Was this reflected in yields/morphology? Why?
0
20
40
60
80
100
0 0.5 1 1.5 2
Cum
mul
ative
%
Aggregate size (mm)
C 1992CT 1992
C 1994
CT 1994
0
20
40
60
80
100
0 10 20 30
Cum
mul
ative
in
filtra
tion
(mm
)
Time (min)
RainfallInfiltration CInfiltration CT
More stable aggregates > 2mm Greater infiltration
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?
Thank you
Beans and concrete