Tour Leader:  Dr Tony Weatherley, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne

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Itinerary

8:15am Meet at Gare 3 at the Melbourne Cricket Ground (MCG)
8:30am Depart via coach for the Western Treatment Plant
9:15am Arrive at the Western Treatment Plant for a tour and presentations
11:30am Morning tea and discussion of Melbourne’s Nitrogen Footprint
11:45am Depart Western Treatment Plant for White Elephant Reserve
12:30pm Arrive White Elephant Reserve, Glenmore
Lunch
2:00pm Depart Glenmore for Yaloak Estate
2:15pm Arrive Yaloak Estate
3:45pm Depart Yaloak Estate
5:00pm Arrive at the Melbourne Cricket Ground

Western Treatment Plant

STOP 1 – Western Treatment Plant

Background to the operation of the plant

The Western Treatment Plant (WTP) was established in 1897 to deal with Melbourne’s growing sewage problem.  Sewage was almost entirely processed at this site until around 1975 when the Eastern Treatment Plant was established at Bangholme. Today the WTP processes around half of Melbourne’s sewage according to strict outfall guidelines for nitrogen. Each year the WTP recycles about 40 billion litres of water. The plant operates in an increasingly urbanized environment and this is imposing additional restrictions on the operation of the ‘farm’. Although land filtration is no longer utilized on site, much of the area is still utilized for sheep and cattle grazing as part of the buffer required between the plant and the ever increasing urban sprawl to Melbourne’s west.

The plant utilizes a system of lagoons to treat sewage. The first lagoon is covered and employs anaerobic processes to break down the sewage. Methane is captured during the process and is harvested to create electricity. As the effluent moves through the plant over a period of around 35 days the nitrogen and phosphorus loads are reduced until the point at which the treated effluent can be discharged to Port Phillip Bay. Some of the treated water is utilized for irrigation of industrial land and parks.

The lagoon system also functions as an extensive wetland that is listed on the Ramsar convention. Most recently the efficiency of nutrient removal has posed problems for wetland function.

 

Click Here to download the paper Mainstream Deammonification at the Western Treatment Plant

Melbourne’s nitrogen footprint and the Western Treatment Plant

Xia (Emma) Liang, FVAS, The University of Melbourne

The following extract relates to methodologies for the determination of the nitrogen footprint of Australia. We shall use this information as a basis for discussion after the main tour of the waste treatment plant.

“For the food component of the N footprint, we estimated the reactive nitrogen (Nr) losses to the environment along the food production and consumption chain, starting with N fertilizer applied to cropland and ending with sewage treatment. The food N footprint has two parts: the food consumption N footprint and the associated food production N footprint. Food consumption was calculated by subtracting Australia’s food waste from food supply. The food consumption N was assumed to be completely excreted since adults generally do not accumulate N in their body.

The amount of N consumed as food in Australia (5 kg N capita-1 yr-1) is similar to other developed countries (5-6 kg N capita−1 yr−1) but higher than that in less-developed countries (Tanzania; 2 kg N capita−1 yr−1). However, Australia and most of the developed countries use advanced wastewater treatment to recycle or convert Nr to the non reactive form, N2, or recycling and reusing it in the form of sludge. This substantially diminishes the discharge of Nr from food consumption to the environment (e.g. the Nr removal factor is 60% in Australia, 79% in Austria, 78% in the Netherlands, and 67% in Germany).”

White Elephant Reserve

STOP 2 – White Elephant Reserve

Understanding an ancient landscape

The White Elephant Reserve resides within the Parwan Valley which itself is part of a complex region of down faulting on the edge of Port Phillip Bay. The area has an annual average rainfall of 530 mm. The White Elephant Reserve was acquired by the Victorian government in 1953 ostensibly to reduce siltation of the nearby Melton dam and to reduce soil erosion. This site provides an excellent opportunity to observe and understand the relationship between topography, vegetation, vermin, erosion and salinity.

The landscape, pre European settlement, has been described as a savannah woodland. At that point a delicate balance existed between the site hydrology and the vegetation. On removal of the native vegetation sheet and gully erosion developed and saline discharges appeared in the low points of the landscape. The figure below shows the landscape prior to remediation. We will discuss the processes at work in this landscape and the landscape management practices that have been put in place to stabilise it.

Yaloak Estate

STOP 3 – Yaloak Estate

Subsoil manuring to ameliorate dense sodic-clay subsoils

Peter Sale1, Renick Peries2, Jaikirat Gill1, Caixian Tang1

1 Department of Agricultural Sciences, La Trobe University

2.Victorian Department of Environment and Primary Industries, Geelong

Introduction

There are large areas of cropping land in south-east Australia with texture-contrast soils (mostly Sodosols (ASC)).  These occur where lighter textured (ie sandy-loam) topsoils overlie poorly structured high clay content subsoils. Frequently the clay subsoils are high in exchangeable sodium and are thus sodic. The physical constraints posed by these dense, sodic-clay subsoils restrict root penetration, thus crop yields are limited. The soils become severely water-logged in wet winters while a dry spring finish results in crops becoming water-stressed resulting in depressed yields.

The practice of subsoil manuring and its effect on dense, sodic-clay subsoils

Subsoil manuring involves the incorporation of high rates of high-N organic material such as poultry litter (up to 20 t/ha fresh weight, with 20% moisture). The amendment is placed in rip-lines around 80 cm apart, into the upper layers of the clay subsoil at depths of around 30-40 cm. This requires a major mechanical intervention in the cropping soil and needs a large logistical effort.  The practice developed because it resulted in large yield increases. The first of these occurred in 2005 when the dryland wheat plots with subsoil manure yielded over 12 t/ha, while the commercial crop yielded around 7 t/ha.

Our research findings, and the results from other studies, suggest that the incorporation of the organic amendment in the clay subsoil increases microbial growth in the amended soil, as the soil microbes are provided with the organic substrate (Clark et al. 2007).

The net effect of the enhanced biological activity in the upper layers of the clay subsoil is a transformation of the clay matrix to a ‘topsoil-like consistency’. The photographs below (Figure 1) are of clay samples, 4 years and 4 months after 20t/ha of the organic amendment had been incorporated at 30-40 cm depth, at a site in Ballan in south west Victoria. The clay layer at this depth in the control plots was dense and hard.  In contrast, the 30-40 cm clay layer in the subsoil-manured plots was soft and friable and was made up of small aggregates (Figure 1).

The results in Figure 1 suggest that as long as there is active, continuing root growth in the amended clay layers, as would occur with continuous cropping, then the effect of subsoil manuring will be long-lasting. The repeated penetration and proliferation of crop roots into this amended clay layer, with each successive crop, might well ensure that aggregation of the clay continues to occur.

Agronomic results

Crop yields

Significant grain yield increases occurred when cereal crops were grown on subsoil-manured plots, compared to the commercial crop. This happened at field sites across the HRZ between 2005 and 2011 (Table 1). In fact, yield increases occurred at every site where a successful crop could be established in the paddock. The increases occurred with canola, on raised beds or on the flat, in south west Victoria (Ballan, Derrinallum, Penshurst, Winchelsea and Wickliffe) and in north east Victoria (Stewarton, Dookie), in wet years (Wickliffe in 2010 – decile 9) and in drought years (Ballan in 2006 – decile 1). The average increase in cereal yields from subsoil manuring over the 7 years was 57%.

The story was the same for the 2012 crop where the grain yield increases exceeded all expectations (Table 2).  This was the year of the ‘dry finish’ which suited subsoil manuring. The yield increases in the subsoil-manured crops in 2012 were around 2 t/ha of canola at one site, more than 4 t/ha of wheat at each of the 3 wheat sites, and 2.7 t/ha at the faba bean site.

Subsoil water

Comprehensive measurements of soil water in the soil profile has indicated that the ‘secret’ to the success of subsoil manuring is the increased availability of water in the subsoil for sustained grain-filling. The advantage of this increased available water has been borne out in the many dry springs experienced in the grain producing regions of southern Australia.

Figure 1. The appearance of the 30-40 cm subsoil clay soil, 4 years after the organic amendment had been incorporated in the layer (A), compared to the clay layer in the control soil (B).

Table 1.  Crop yields for commercial and subsoil-manured cereal crops, at sites across Victoria, 2005-11

 

 

Year

 

 

Site

 

 

Crop

 

Grain Yield (t/ha)

Commercial

crop

Subsoil

manured 1

Increase

in yield

Increase

(%)

2005 Ballan Wheat (1st crop) 7.6 12.5 5.3 70 %
2006 Ballan Wheat (2nd crop) 3.6 5.6 2.0 55 %
2009 Derrinallum Wheat (1st crop) 5.0 9.8 4.8 96 %
2009 Penshurst Wheat (1st crop) 4.8 7.6 2.8 58 %
2009 Winchelsea Barley (1st crop) 4.4 7.7 3.4 77 %
2010 Wickliffe Wheat (1st crop) 9.1 11.6 2.5 27 %
2011 Derrinallum Wheat (3rd crop) 5.0 7.4 2.4 48 %
2011 Stewarton Wheat (1st crop) 5.7 8.1 2.4 42 %
Av. for cereals 5.6 8.8 3.2 57 %
 

1 Subsoil manured plots received 20 t/ha (fresh weight) of an N-rich organic amendment (less than 20% moisture content) which was incorporated in rip-lines, 80 cm apart, at a depth of 30-40 cm in the subsoil.

Evidence that there was an increase in the volume of deep subsoil water extracted from the subsoil layer in the subsoil-manured plots is provided in Table 3.  The extraction occurred after crop flowering, which is a crucial stage of crop development, and explains why the large yields occurred on subsoil manured plots in 2012. In practically every case where large grain yield responses occurred in 2012, there was also a significant increase in the volume of soil water that was extracted from the 50-100 cm deep subsoil layer (Tables 2, 3).

Conclusions

Subsoil manuring is a new farm practice that improves the physical fertility of dense, sodic-clay subsoils, which occur across large cropping areas in south eastern Australia. We suggest that the improvement in the structure of the dense sodic-clay results from microbial-induced aggregation of the clay. This improves the porosity of the clay which in turn encourages root penetration and root activity. Crops are then able to extract previously-unavailable subsoil water.  The net effect is a marked increase in the ‘bucket size’ of the soil profile.

Table 2.  Summary of crop yields for commercial and subsoil-manured crops, at sites across Victoria in 2012

 

Year

 

Site

 

Crop and crop no.

following intervention

 

Grain Yield (t/ha)

Commercial

crop

Subsoil

manured 1

 

Increase

in yield

Increase

(%)

2012 Penshurst Canola (4th crop) 2.3 4.3 2.0 87 %
2012 Derrinallum Wheat (4th crop) 6.3 10.4 4.1 65 %
2012 Stewarton Wheat (2nd crop) 4.9 9.4 4.5 92 %
2012 Dookie Wheat (2nd crop) 5.3 9.4 4.1 77 %
2012 Wickliffe Faba beans (3rd crop) 4.4 7.7 3.4 77 %
 

 1 Subsoil manured plots received 20 t/ha (fresh weight) of an N-rich organic amendment (less than 20% moisture content) which was incorporated in rip-lines, 80 cm apart, at a depth of 30-40 cm in the subsoil.

The practice resulted in large, consistent and continuing crop yield increases at sites across the Victorian HRZ. These responses meant that subsoil manuring with 20 t/ha of poultry litter, or with the half rate of 10 t/ha, was profitable and financially feasible, with net benefits above alternative uses of land and capital. The intervention resulted in a reasonably prompt return to positive net cash flow. These findings are quite illuminating, given the earlier view that any attempt to modify the properties of subsoils would be exorbitantly expensive and unlikely to be profitable or financially feasible.

The costs of subsoil manuring with 20 t/ha of poultry litter, are estimated to be very high in excess of $1200/ha for the farms in this analysis. However the large increases in grain yield, occurring each year over the four year period, plus savings on fertiliser use, meant that there were large economic and financial benefits from this practice. There is now an urgent need for industry research to determine whether processed crop residues, or other farm sources of plant material, could be used as alternative subsoil amendments to lower subsoil manuring costs and to reduce the reliance on animal manures.

The analysis shows that the farmers at these two grain farms were likely to be substantially better off, as a result of investing in subsoil manuring in their paddocks in 2009. These results will increase the interest in subsoil manuring in the HRZ. The extent to which the costs can be contained, and the logistics streamlined, will determine the degree to which the practice will be adopted.

References

Clark GJ, Dodgshun N, Sale PWG, Tang C (2007) Changes in chemical and biological properties of a sodic clay subsoil with addition of organic amendments. Soil Biology and Biochemistry 39, 2806–2817

Gill JS, Sale PWG, Peries RR, Tang C (2009) Changes in physical properties and crop root growth in dense sodic subsoil following incorporation of organic amendments. Field Crops Research 114, 137-146

Kirkegaard JA, Lilley JM, Howe GN, Graham JM (2007) Impact of sub soil wateruse on wheat yield. Australian Journal of Agricultural Research 58, 303–315

Passioura JB (1976) Physiology of grain yield in wheat growing on stored water. Australian Journal of Plant Physiology 3, 559–565

SAFETY

All visitors to the Western Treatment Plant must wear the following essential clothing while on site:

  • Long pants / trousers.
  • Flat, enclosed footwear. Sandals or thongs are not permitted on-site. Shoes with heels are not recommended. Long sleeves are advisable.

Failure to comply with the above clothing requirements can result in exclusion of participants from exiting the bus on tour.

Visitors should also bring:

  • Clothing appropriate to protect against weather including sunscreen, hat and raincoat or rain jacket (as required).

Accessibility

Tours of the Western Treatment Plant are suitable for those with a walking disability (i.e. requiring a wheelchair, walking frame or similar aid).

Emergencies

Melbourne Water Education Officers will evacuate the group in an emergency.

In an emergency, visitors should adhere to the instructions given by designated fire wardens (identified by yellow hard hats and high visibility vests).

Public liability cover

Melbourne Water has the appropriate public liability cover.