Information

The effect of crop type, crop rotation, and tillage practice on runoff and soil loss on a Vertosol in central Queensland – Capella

Level 1 General description

Purpose:

A large scale catchment study was established to measure runoff and soil loss under wheat, sorghum and sunflower cropping and zero, reduced and conventional tillage practices.

Methods (brief)

Runoff and soil erosion were monitored over 12 years on 9 catchment areas, separated by broad-based contour banks. The experiment had 9 treatments – sorghum, sunflower and wheat each grown with varying tillage conditions.

Sallaway et al. (1988) developed techniques to estimate vertical projection of cover and stubble weight.

Sallaway et al. (1990) examined the response of runoff and peak runoff rate in terms of the interactive effects of the independent variables using multiple-regression analysis.

Murphy et al. (In Press) Runoff and sediment yields were also examined under single, double, and triple contour bank slope lengths for a zero-till CTF system.

Key findings (brief)

The study found that wheat cropping had lower average annual runoff and soil loss than sorghum and sunflower. Zero and reduced tillage retained more crop stubble and had less soil loss than conventional tillage. The zero tillage wheat treatment had the lowest average annual runoff and soil loss, and conventional sunflowers had the highest.

Sallaway et al. (1988) found that projected cover post-harvest is a function of crop species and seasonal effects as expressed in grain yield, and was in the order wheat (90.3), sorghum (58.5) and sunflower (43.1). Projected cover was linearly related to grain yield.

Sallaway et al. (1990) found that the main factor affecting runoff volume was total rainfall, whilst peak runoff rate was mainly determined by rainfall intensity. The other variables had smaller, interactive effects. The major effects of the management practices were soil water deficit on total runoff and surface cover on peak runoff rate.

Murphy et al. (In Press) Standard spaced slope lengths were more effective for reducing soil loss compared to double and triple spaced lengths.  Under conditions conducive to runoff, double and triple spaced slope lengths produced 60 and 57 % more until soil loss than single spaced slope length.

Table 1. Summary of Average Annual Runoff and Soil Erosion for Capella catchment study. Results presented for trial period annual average 1984-1989. Slope length was 130m and slope percentage was 2% (Freebairn and Cutajar, 2012).

Description of Management system

Management Class

Simulated

Description of Management system

LS1

Observed

EMC 1

 

gm/L

Normalised2 Soil loss

t/ha

Normalised3 EMC

gm/L

Runoff

Off-site sediment delivery

Runoff

Sediment loss

(mm)

(t/ha)

(mm)

(t/ha)

Winter zero tillage

B

 

21.2

0.33

Zero Tillage

(Bays 2 and 9)

0.3

 

18.7

1.42

7.6

4.7

25.3

Summer zero tillage

B

14.5

0.34

Winter reduced tillage

C

 

29.9

1.5

Reduced tillage

(Bays 3, 5 and 8)

0.3

23.1

1.92

8.3

6.4

27.7

Summer reduced tillage

C

 

18.1

1.2

Winter conventional tillage

D

38.5

5.6

Conventional tillage

(Bays 4, 6 and 7)

0.3

28.4

4

14.1

13.3

46.9

Summer conventional tillage

D

23.6

3.8

Opportunity Crop

A

13.8

0.33

-

0.3

-

-

-

-

-

1 Soil loss divided by runoff, primary sediment source, no allowance for deposition.

2 USLE factor used to correct normalised data to an LS =1

3 EMC normalised to an LS =1

Location

Catchments located near Capella in the Peak Downs Shire of the central highlands 23.06’S, 148.02’E.

Related studies

N/A

 

Level 2, Level 3, Level 4 and Level 5