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 MooreCSIRO Sustainable Agriculture Flagship

WCCA, Brisbane, 26-29 September 2011

Presentation overview

IntroductionStudy region: South Australian MalleeObjectives

Materials and MethodsAusFarm modelTypical farm for the Mallee

ResultsFeed gapsEffect of cereal grazing

Conclusions

Study regionMallee agro-ecological zone, south-eastern Australia Mediterranean climate; 250-350 mm per yearHigh soil variability: dune (coarse soils) - swale (heavy soils) landscapesMixed farming: cereals (wheat, barley) + sheep & pastures (Medics)

SA VicProportion of arable land cropped (%) 57 72Proportion of arable land expected to be cropped in 10 years (%) 63 76Farmers keeping sheep (%) 85 56Farmers keeping >1000 head of sheep (%) 54 43Farm area managed (arable ha) 2550 3090

Introduction

Introduction

Constraints to farmingHigh 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

Introduction

ObjectivesTo 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

Materials and Methods

AusFarm: Crop-livestock farm system model

Multiple paddocks & rotationsScripting language for farm management rulesLong term climate data ; year-to-year variability

AusFarm

Apsim

Soil waterSoil nutrientsCrop dynamics

Grazplan

Pasture dynamicsLivestock dynamics

Manager

Apsim: Keating et al., 2003www.apsim.info

Grazplan: Freer et al., 1997; Moore et al., 1997www.grazplan.csiro.au

Building a “typical” farm modelRegional expert panelQuestionnaire to capture land use, management rules, production

expectations“Validation” of model outputs– literature values– iterative feedback process with expert panel

Feed gap analysisCompare feed supply with feed demandFeedbase and supplement intake

Effect of cereal grazing on the feedbaseComparing baseline scenario with cereal grazing scenario

Materials and Methods

“Typical” farm for the dry end of the MalleeLocation: WaikerieRainfall: 252 m per year

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Annual rainfall

Monthly rainfall

Long-term average

Results

“Typical” farm for the dry end of the MalleeLocation: WaikerieRainfall: 252 m per yearTotal area: 2000 haSoils: Dune (50%) and Swale (50%) soils Land use: 1/3 pasture; 2/3 cerealsRotation: Wheat / Barley / PastureSelf 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

Results

Feed gapsPasture supply vs demandMajor feed gaps in summer and autumn

Results

MLA feed calculatorLambing time

Feed gapsFeedbase: intake of various feed types

Results

Grazing cereals10% 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

Results

Grazing cereals

Results

Lambing time

Grazing cereals

Results

Dual purpose, winter wheat Spring variety

Grazing days 27 34Cereal forage intake (kg/ewe/yr) 32 41Supplement intake (tonnes/farm/yr) 222 * 208 *Yield penalty on dune soil (kg/ha) 476 618Yield penalty on swale soil (kg/ha) 246 303

* Statistically significant decrease in supplement intake from baseline scenario of 257 tonnes per year

Grazing cerealsDual-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

Results

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

Conclusions

Thank you!