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