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Sustainable sheep production in Mallee farming systems

Roy Latta

Future Farming Systems Research, DPI, Victoria, Walpeup Vic. 3507, Australia. Roy.Latta@dpi.vic.gov.au

Abstract

A one year grazing study comparing annual pastures with forage crops and lucerne supplements found there is an opportunity for the Mallee region of SE Australia to capture economic benefits through increasing stocking rates. Rotating ewes and lambs from an annual pasture onto a lucerne or forage crop pasture supported a 50% increased stocking rate compared to rotating onto an annual pasture. Grazing the forage crop and lucerne maintained similar weight profiles with less supplementary grain than animals on the annual pasture. However the annual pasture groundcover was reduced to approximately 20% irrespective of stocking rate and grazing period prior to crop stubbles becoming available for grazing. The results of study indicate the opportunity to double current stocking rates is viable but requires stock containment strategies to ensure the protection of the land resource.

Key Words

Annual pasture, lucerne, forage crops

Introduction

Studies by Robertson and Wimalasuriya (2004) have shown the potential for doubling stocking rates from the current Mallee regional average of <1 ewe/winter grazed hectare. Latta and Carter (1998) found that increasing stocking rates on annual medic pastures in a pasture crop rotation resulted in higher cereal grain yields and grain protein %. However, there is concern about the environmental impact of increased livestock numbers on soil stability and potential erosion. Maintaining >50% plant groundcover is recommended (Leys, 2002).

The study at Walpeup set out to establish production opportunities and land protection impacts of increasing stocking rates in the central Mallee region of south-eastern Australia. It utilises a regenerating annual medic pasture plus lucerne and forage supplements to ascertain the opportunities and benefits for mixed farming enterprises in low rainfall regions of SE Australia. This report covers the results from the first year of the investigation (2006).

Methods

Experimental site

The experiment was conducted at the Mallee Research Station, Walpeup, Victoria (35.8oS, 142oE, altitude 50m). The soil is calcareous earth (Gc1.22; Northcote, 1979) with pH 7.7 (H2O) at 0-0.1m.

Treatments

The treatments in Spring 2006 were:

  • 6 ewes and 6 lambs rotated on one 3 ha annual pasture paddock and one 3 ha pasture paddock with selective grass control applied;
  • 6 ewes and 6 lambs rotated on one 3 ha annual pasture paddock and one 1 ha sown forage crop paddock;
  • 6 ewes and 6 lambs rotated on one 3 ha annual pasture paddock and one 1 ha lucerne paddock.

Glyphosate at 0.3L/ha (450 g a.i./L) was applied to treatments 1, 2 and 3 annual pasture plots on 7 September to restrict the seed set of annual grasses. Selective grass control was applied to the second 3 ha treatment annual pasture paddock on 14 August (0.1 L/ha Verdict 520 g a.i./L) to control annual grasses.

On 11 August 2006 a group of 18 ewes were selected from a flock of 45 on the basis of having a mean weight 50 kg 3 kg and of having a single lamb. They were randomly allocated to the 3 annual pasture plots and provided a grain feed supplement until 29 August. On 29 August sheep and lambs were placed into the second component of their treatments; (1) selective grass controlled annual pasture until 15 October (2) sown forage crop until 1 October and (3) lucerne based pasture until 30 October when they were returned to their respective annual pasture plots (Table 1). Hand feeding was continued on treatment 1. All lambs were removed and sold at a mean 40 kg liveweight on 21 September (at approximately 16 weeks of age). Ewes continued to be maintained on their respective treatments, but not supplementary fed, until 22 November when crop stubbles became available following harvest.

Table 1. Grazing period on each component of the 3 treatments in 2006

 

August

September

October

November

Treatment 1

Annual Pasture

Annual Pasture (GC*)

Annual Pasture

Treatment 2

Annual Pasture

Forage crop

Annual Pasture

Treatment 3

Annual Pasture

Lucerne

Annual Pasture

(GC*) Grass cleaned with selective chemical

Supplementary feeding

Ewes and lambs were hand fed from 11 to 28 August (treatments 2 and 3) or 22 September (treatment 1). A total rate of 5 kg/ewe/week of both grain and hay, with 20 and 8.5% analysed crude protein and 12.8 and 11 (MJ/kg DM) of metabolisable energy (Feedtest, VicDPI) respectively was fed in equal amounts 3 times a week, Monday, Wednesday and Friday.

Pasture establishment and measurements

The annual pasture was a regenerated annual medic based pasture. The 2006 lucerne pasture treatment was established in 2004 in a neighbouring paddock with cv. Hunterfield sown at 2 kg/ha. One hectare was selected and fenced within the 26 ha paddock. The 1 ha forage crop was sown to a mixture of oats cv. Wallaroo at 50 kg/ha and vetch cv. Morava at 25 kg/ha on 28 June in a fenced area outside the 12 ha of annual pasture but within the 24 ha paddock. Phosphorus (12 kg P/ha) and N (6 kg N/ha) were applied at sowing.

Five 0.2 m2 quadrats were harvested with blade shears to ground level each 4 – 6 weeks. Samples were sorted to remove any soil, dead or root material, dried at 60oC and weighed. Ground cover percentage, using the levy point technique (Levy and Madden 1933) were collected each 4 – 6 weeks at 50 random sites in each treatment.

Statistical analysis

Analysis of variance (ANOVA) using Genstat 5 (Genstat, 2002) was used for groundcover measurements with treatment x time as the treatment structure, replicate/time as the block structure. This took account of the correlation between measurements on successive occasions in the same field plot. Similar animal numbers on different sized treatments was analysed as 6 replicates of individual animals. Pasture measurements were presented as means of the 5 sub-plots assessed within the single replicate.

Results

Rainfall

In 2006, April and early May rainfall initiated annual pasture regeneration and the establishment of the forage crop. However, a total of 90-mm growing season rainfall in 2006 severely restricted pasture production (Table 1).

Table 2. Monthly, growing season (GSR), annual (2006) and long-term average rain (LTA) (mm)

J

F

M

A

M

J

J

A

S

O

N

D

GSR

Annual

2006

22

1

13

22

14

2

37

1

14

0

19

28

90

173

LTA

20

26

22

23

32

30

33

35

32

35

27

22

230

337

Biomass production

Table 3. Available annual pasture, forage crop and lucerne biomass (t DM/ha) in response to 2006 stocking rate treatments

   

1 Aug.

30 Aug.

25 Sept.

14 Nov.

Treatment 1

Annual Pasture

0.2

0.4

 

0.2

Treatment 1

Annual Pasture GC*

0.3

0.3

 

0.2

Treatment 2

Annual Pasture

0.3

0.4

 

0.3

Treatment 2

Forage crop

 

0.4

0.1

 

Treatment 3

Annual Pasture

0.3

0.5

 

0.4

Treatment 3

Lucerne

 

0.3

0.2

 

The available annual and lucerne pasture biomass in 2006 was maintained at or > 0.2 t DM/ha by rotating into the companion paddocks. The forage crop biomass was reduced to 0.1 t DM/ha.

Animal production

Individual ewe and lamb liveweights were similar irrespective of pasture treatments and associated stocking rates until the removal of the lambs in September. The cessation of handfeeding at that time resulted in the annual-lucerne pasture treatment maintaining higher ewe liveweight than the annual pasture treatment irrespective of the earlier removal of supplementary feeding.

Figure 1. Mean of individual liveweights (kg) of ewes (filled symbols) and lambs (open symbols) in response to treatments 1 ● ○, 2 ■ □ and 3 ▲ ∆ over the course of the 2006 study. LSD (P=0.05) shown by bar.

Groundcover

Figure 2. Groundcover (%) in response to treatments 1 (●) 2 (■) and 3 (▲) in 2006.

All 3 stocking rate treatments had comparable groundcover percentages throughout study. The groundcover declined from 60% in July to near 30% in September when the sheep were rotated to their companion paddocks. The return of the ewes to the treatments resulted in groundcover being reduced to around 20% in November irrespective of total grazing time (Table 2).

Discussion

In 2006, an attempt was made to evaluate options to maintain livestock numbers in mixed systems with reducing available winter grazing areas as documented by Ewing and Flugge (2004). A forage crop and a lucerne pasture to provide increased biomass production were considered feasible options for the Mallee region based on the survey of Robertson and Wimalasuriya (2004). The drought conditions of 2006 resulted in 1 ewe and lamb/winter grazed ha being the base stocking rate treatment and the recommended lactating ewe grain and hay feed supplement was required. The forage crop and lucerne allowed a 1.5 ewe and lamb/winter grazed ha stocking rate with a slightly reduced period of supplementary feeding. These treatments resulted in a similar outcome in terms of lamb liveweight gain/meat production from all treatments.

A merino ewe prime lamb enterprise is a diversification option for the Mallee. Even in the drought of 2006, 60 kg of lamb/ha with an extra cost of $15-20/ha supplementary feeding compares more than favourably with the negative cropping returns of that year as a result of wheat yields <0.5 t/ha, plus there is the benefit of the legume pasture break crop.

The study has delivered important outcomes for both economic and environmental consideration. Significant increases in district stocking rates (based on survey data from Robertson and Wimalasuriya, 2004) were shown to be achievable. There are however more considerations than just maximising the animal production from the growing season. According to Leys et al. (2002), 50% groundcover with associated ground “roughness” is required to stabilise Mallee sandy loams. The 2006 drought conditions meant sheep were fed in containment areas from crop seeding in May until 18 August when they were placed onto annual pasture treatments. Sheep were rotated at the end of August onto their respective annual pasture, forage or lucerne paddock. The duration of the grazing period on the second paddock varied from 4 weeks to 8 weeks before they were returned to their original annual pasture paddocks where they remained until the 22 November. Irrespective of the time spent on those annual pasture paddocks ground cover of all treatments was near to 20% at the time of the animals’ removal and transfer to crop stubbles.

Sustaining a viable livestock industry in the region is reliant on achieving the best utilisation of the remaining pasture areas to ensure industry diversification and risk management strategies. A key component of the strategy is the widespread use of stock containment areas to protect the groundcover during the critical autumn and late spring/early summer periods when up to 80% of the farm, the cropping area, is not available to livestock.

Acknowledgements

I acknowledge technical support from Ron Sly and Cassey Weston, and funding support from Grain and Graze Mallee project and Victorian DPI.

References

Ewing MA and Flugge F (2004) The benefits and challenges of crop-livestock integration in Australian agriculture. New directions for a diverse planet: Proceedings of the 4th International Crop Science Congress Brisbane, Australia, 26 Sep – 1 Oct 2004 www.cropscience.org.au

Genstat (2002) ‘Release 6.1 Reference manual.’ (Lawes Agricultural Trust: Rothamstead, UK).

Latta RA and Carter ED (1998) Increasing production of an annual medic-wheat rotation by grazing and grass removal with herbicides in the Victorian Mallee. Australian Journal of Experimental Agriculture. 38: 211-217.

Levy EB and Madden EA (1933) The point method of pasture analysis. New Zealand Journal of Agriculture. 20: 267-279.

Leys JF, Semple WS, Raupach MR, Findlater P and Hamilton GJ (2002) Measurement of size distributions of dry soil aggregates. In “Soil physical measurement and interpretation for land evaluation”. Australian soil and land survey handbook series: Vol.5.

Robertson SM and Wimalasuriya RK (2004) Limitations to pasture and sheep enterprises and options for improvement in the Victorian Mallee. Australian Journal of Experimental Agriculture. 44: 841-849.

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