idenitifying the fit for perennial forage options in a crop-livestock system: use of a whole-farm...

Identifying the fit for perennial forage options in a crop-livestock system: use of a whole-farm optimization model

Marta Monjardino,

R. Llewellyn and A. Bathgate

5th World Congress of Conservation Agriculture Brisbane, 26-29 September 2011

Background

• Major economic and environmental challenges in low rainfall zones of southern Australia;

• Forage shrubs may help fill the long feed gap in the Mallee and provide other benefits;

• But are they profitable? • Use of a bio-economic tool to help identify where in the

landscape and at what level of production/quality they might be profitable.

CSIRO. Identifying the fit for forage shrubs in a crop-livestock system: use of a whole-farm optimization model

Forage shrubs in the Mallee

• Old Man Saltbush (Atriplex nummularia) the most widely available commercial shrub species;

• Low % of farmers adopting shrubs and only <1% of farm area with shrub plantings due to relatively low quality/production;

• Opportunities to identify/develop new OMS and other shrub types, arrangements and mixes for higher performance;

• Whole-farm model needed as perennials will always be a niche land area, but have whole-farm impact via livestock, etc;

• Whole-farm considerations to help shape R&D strategies.


MIDAS

• Model of an Integrated Dryland Agricultural System;• Whole-farm optimization model;• Based on LP technique;• Deterministic model;• Annual equilibrium structure; • Interactions between enterprises;• Thousands of input parameters;• Detailed model output;• Software: EXCEL spreadsheets + LINDO algorithm;• Good coverage of southern Australia agro-ecological regions

with several model versions in 4 states.


Mallee MIDAS overview

• Typical 3000 ha crop/livestock farm;• Average annual rainfall: 250-350 mm (80% in winter);• Average summer max daily temp. >30ºC;• 7 LMUs with ≠ prod. potential in typical dune-swale land system;• Crops: wheat, barley, triticale, canola, lupins, range of legumes;• Options for fallow and cereal grazing;• Merino/crossbred sheep dominant livestock for wool and meat;• Grazing on annual (medic), perennial (lucerne), vol. pastures;• Woody perennial options: forage shrubs, tree alleys;

0

10

20

30

40

50

60

70

Rai

nfal

l (m

m) &

tem

pera

ture

('C

)

Rainfall

Temperature



• Over 200 crop-pasture rotations + inter-rotational effects;• Ten pasture growing periods/year;• Ten major feeding periods/year;• Five supplementary feeding options;• Over 80 sheep classes;• Different management options/class;• Different energy and intake volume/class;• Deferment of pasture grazing between growing periods, and

degeneration of feed over summer;



• Several grain, stubble and wool quality classes;• Soil N balance and fertilization options;• Chemical control of diseases, pests and weeds;• Groundwater recharge and surface water run-off;• Loss of top soil by erosion;• Machinery specifications;• Labour requirements;• Farm finance.


Validation

• Difficult validation of optimization models;• Extensive process of verification;• Expert assessment of input parameters and k.p.i. (e.g. whole-

farm profit, crop/pasture %, SR, rotations/LMU);• Comparison with actual farming practice;• Many issues analyzed with MIDAS/MUDAS over 3 decades, e.g.:

• New crops in rotation, e.g. lupins, canola;• Saltland pastures;• Trees and shrubs;• Soil management, e.g. deep ripping;• Impact of agric. policies, e.g. salinity tax, C price;• Livestock breeds, e.g. Awassi, Dorper;• Livestock management, e.g. time of lambing;• Impact of grain quality; • Machinery changes;• Conservation strategies, e.g. stubble retention.


Modelling shrub-based systems

• Biological traits • Productive life of the stand• Shrub density• Shrub growth rate/biomass production• Re-establishment period• Nutritive value and anti-nutritional effects• Proportion of understorey pasture

• Animal impact • Liveweight gains due to permanent feed on offer • Increased lambing rate from extra shade and shelter

• Environmental impact• Groundwater recharge• Top soil loss by erosion

• Costs• Establishment /maintenance of shrub stand


Land management units

LMU Main soil type Description W yield potential

Shrub potential

U/s medic pasture

potential

1234567

Sandy loamSandyCalc, stonyInterm. SoilsDeep sandsLo o/ clay (w/ ssc)Lo o/ clay (no ssc)

Reliable, ↑ yieldsSame, but fert req.↓ yld, wears mach.Med yieldsErosion, ↓ yields↓↓ yld in dry spring↓ yld in dry spring

2.01.80.41.60.80.61.4

100%70%50%90%50%65%90%

100%67%10%67%17%40%

>100%


Area of shrubs allocated to each LMU as they increase on the farm.


0 10 20 30 40 50 60

0

500

1000

1500

2000

LMU 7

LMU 6

LMU 5

LMU 4

LMU 3

LMU 2

LMU 1

Shrub %

Sh

rub

are

a (h

a)

Standard output

Crop area (% of farm)Pasture area (% of farm)Shrub area (% of farm)Stocking rate (DSM/ha of farm)Supplementary grain feed (kg/DSE/yr)Groundwater recharge (mm/ha/yr)Topsoil loss by erosion (m3/ha/yr) Profit ($/ha/yr)

56440

2.465

17490

129


Key model parameters

Parameters Std

Saltbush density (plants/ha)Saltbush nutritive value (MJ ME/kg DM)Saltbush biomass production (kg DM/plant)Saltbush anti-nutritional effects on intake (%)Saltbush establishment cost ($/plant)Price of wheat ($/t ASW)Price of wool (c/kg clean WMI)Price of prime lamb ($/kg DW)

1500713

0.4280900

4


Key model parameters - SA

Parameters Min Std Max

Saltbush density (plants/ha)Saltbush nutritive value (MJ ME/kg DM)Saltbush biomass production (kg DM/plant)Saltbush anti-nutritional effects on intake (%)Saltbush establishment cost ($/plant)Price of wheat ($/t ASW)Price of wool (c/kg clean WMI)Price of prime lamb ($/kg DW)

00.2180700

3

1500713

0.4280900

4

3000103

4801100

6


Change in whole-farm profit with increasing % saltbush shrubs.


0 10 20 30 40 50 60

0

200000

400000

600000

Shrub %

Wh

ole

-far

m p

rofi

t ($

/yea

r)

Change in whole-farm profit with increasing % saltbush shrubs.


0 10 20 30 40 50 60

0

200000

400000

600000

Shrub %

Wh

ole

-far

m p

rofi

t ($

/yea

r)

<10% shrub area => small decline in profit; >10% shrub area => sharp decline in profit

Impact of different saltbush plant density levels and establishment costs on whole-farm profit with higher % shrubs.


Impact of different saltbush biomass production and nutritive value levels on whole-farm profit as % shrubs increases on the farm.


0 10 20 30 40 50 60

0

200000

400000

600000

3 kg DM/plant

2 kg DM/plant

1 kg DM/plant

0.5 kg DM/plant

Shrub %

Wh

ole

-far

m p

rofi

t ($

/yea

r)

Impact of prime lamb price change on whole-farm profit for a range of shrub areas.


0 10 20 30 40 50 60

0

200

400

600

800

Deepflow

Erosion

Shrub %

Un

its/

/ha/

yr

Impact of wheat price change on whole-farm profit for a range of shrub areas.


0 10 20 30 40 50 60

0

200

400

600

800

Deepflow

Erosion

Shrub %

Un

its/

/ha/

yr

Changes in ground water recharge (mm/ha/yr) with an increasing shrub area on the farm.


0 10 20 30 40 50 60

0

200

400

600

800

Deepflow

Erosion

Shrub %

Un

its/

/ha/

yr

0 10 20 30 40 50

0

200

400

600

800

Shrub %

mm

//h

a/yr

Conclusions

1. At current production/quality levels, shrubs are marginally profitable at up to 10% of farm, i.e. shrubs in the Mallee can be introduced on small farm areas (≤ 10%) with minimal loss in profit.


Conclusions


2. Profitability of forage shrubs depends on opportunity cost of giving up other farm enterprises in the poorer farm soils;


Conclusions


2. Profitability of forage shrubs depends on opportunity cost of giving up other farm enterprises in the poorer farm soils;

3. The current profit shortfall may well be made up through:• R&D to improve increases in shrub quality/production, as well

as more effective shrub mixes/arrangements;• Lower shrub establishment costs;• Capturing of other benefits such as GHG emissions reduction

(C seq. and lower CH4 via bioactive compounds), animal health/performance, improved soil condition, biodiversity, labour management, and spread of farm risk.

• A change in market prices, e.g. lower grain and higher animal prod. prices.



Photo source: Enrich project

Contact UsPhone: 1300 363 400 or +61 3 9545 2176

Email: [email protected] Web: www.csiro.au

Thank you!

CSIRO Ecosystem SciencesDr. Marta Monjardino

Phone: 61 (0)8 8303 8413Email: [email protected]: www.csiro.au/ces

Acknowledgements Future Farm Industries CRCGRDC

idenitifying the fit for perennial forage options in a crop-livestock system: use of a whole-farm...

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croppasture rotations