Presentation from the WCCA 2011 conference in Brisbane, Australia.

1. Feed gaps and the effect of cereal grazing in a dryland
farming system of the South Australian Mallee –
a crop-livestock model application
Katrien Descheemaeker, Andrew Moore
CSIRO Sustainable Agriculture Flagship
WCCA, Brisbane, 26-29 September 2011

2. Presentation overview
Introduction
Study region: South Australian Mallee
Objectives
Materials and Methods
AusFarm model
Typical farm for the Mallee
Results
Feed gaps
Effect of cereal grazing
Conclusions

3. Introduction
Study region
Mallee agro-ecological zone, south-eastern Australia
Mediterranean climate; 250-350 mm per year
High soil variability: dune (coarse soils) - swale (heavy soils) landscapes
Mixed farming: cereals (wheat, barley) + sheep & pastures (Medics)
SA Vic
Proportion of arable land cropped (%) 57 72
Proportion of arable land expected to be cropped in 10 years (%) 63 76
Farmers keeping sheep (%) 85 56
Farmers keeping >1000 head of sheep (%) 54 43
Farm area managed (arable ha) 2550 3090

4. Introduction
Constraints to farming
High spatial (soil quality) and temporal (climate) variability
Major feed gaps in bad years; feed supplementation limits farm profitability
Identifying solutions?
Integrated simulation models as R&D tool to
– Describe and understand farming systems, their components and interactions
– Identify gaps, bottlenecks
– Assess the potential effect of interventions

5. Introduction
Objectives
To use the AusFarm whole farm system model to simulate long term crop,
pasture and animal production for a typical farm in the SA Mallee,
To use the model as a tool to characterize the feedbase and feed gaps
throughout the year,
To use the model as a tool to assess the potential for cereal grazing to
overcome feed gaps

6. Materials and Methods
AusFarm: Crop-livestock farm system model
AusFarm
Manager
Apsim Grazplan
Apsim: Keating et al., 2003
Soil water Pasture dynamics www.apsim.info
Soil nutrients Livestock dynamics
Crop dynamics Grazplan: Freer et al., 1997;
Moore et al., 1997
www.grazplan.csiro.au
Multiple paddocks & rotations
Scripting language for farm management rules
Long term climate data ; year-to-year variability

7. Materials and Methods
Building a “typical” farm model
Regional expert panel
Questionnaire to capture land use, management rules, production
expectations
“Validation” of model outputs
– literature values
– iterative feedback process with expert panel
Feed gap analysis
Compare feed supply with feed demand
Feedbase and supplement intake
Effect of cereal grazing on the feedbase
Comparing baseline scenario with cereal grazing scenario

8. Long-term average
“Typical” farm for the dry end of the Mallee
Monthly rainfall
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
Rainfall: 252 m per year
1989
1988
1987
1986
1985
1984
1983
Location: Waikerie
1982
1981
1980
1979
1978
1977
1976
1975
1974
1973
1972
1971
1970
1969
1968
1967
1966
Results
1965
1964
1963
1962
1961
1960
Annual rainfall
1959
1958
1957
1956
1955
1954
1953
1952
1951
1950
0
100
600
500
400
300
200

9. Results
“Typical” farm for the dry end of the Mallee
Location: Waikerie
Rainfall: 252 m per year
Total area: 2000 ha
Soils: Dune (50%) and Swale (50%) soils
Land use: 1/3 pasture; 2/3 cereals
Rotation: Wheat / Barley / Pasture
Self replacing Merino flock of ~ 1600 animals
( ~ 0.8 animals per farm ha)
Animals graze medic pastures and stubble after
harvest
Supplements are fed to maintain body condition above
critical state

10. Results
Feed gaps
Pasture supply vs demand
Major feed gaps in summer and autumn
Lambing time MLA feed calculator

11. Results
Feed gaps
Feedbase: intake of various feed types

12. Results
Grazing cereals
10% of the “typical” farm
Comparison of 2 soil types: dune (100ha) and swale (100ha)
Early sowing: beginning of April
2 wheat varieties
• Dual purpose winter wheat variety (long vegetative growth
stage; Wedgetail)
• Spring wheat variety (conventionally used in the Mallee; Mace)
Grazing assumptions:
• Start: when biomass > 500 kg/ha and not plenty of pasture
• End: when biomass < 200 kg/ha, max of 3 weeks
• Dual-purpose variety: Zadoks growth stage < 30 (before stem
elongation)
Flat fertilizer rate: 30 kg N/ha

13. Results
Grazing cereals

14. Results
Grazing cereals
Lambing time

15. Results
Grazing cereals
Dual-purpose winter wheat: not suited to Mallee environment
-Season is too short
-High grain yield penalties compared to conventional variety
Spring variety: intended as forage to fill early winter feed gap
-Grain yields not much considered
-Suitable on poorer soils and with low inputs
Dual
purpose, winter
wheat Spring variety
Grazing days 27 34
Cereal forage intake (kg/ewe/yr) 32 41
Supplement intake (tonnes/farm/yr) 222 * 208 *
Yield penalty on dune soil (kg/ha) 476 618
Yield penalty on swale soil (kg/ha) 246 303
* Statistically significant decrease in supplement intake from
baseline scenario of 257 tonnes per year

16. Conclusions
AusFarm is a useful tool to understand mixed crop-livestock
systems
-Allows crop, pasture and animal models to “talk” to each
other
-Allows complex farm management rules to be captured
Feed gaps were diagnosed by
-Comparing feed supply with demand
-Assessing feedbase and supplement intake
In the Mallee, feed gaps
-occur over summer through to early winter
-are a major risk factor
Early sowing of cereals on part of the farm has potential to
-Produce good quality forage in May-June
-Reduce reliance on supplementary feeding

17. Thank you!