rt kilter finaltechoutcomes aotgr1-167 draft (44876) · project outline acceptance and release...

Sequestering Soil Carbon in an Irrigated Landscape turned Dry Ecological Grazing

Project Outcome

Project AOTGR1-167

Technical Report No. 9

February 2016

Version 1.0

Project Outline ACCEPTANCE AND RELEASE NOTICE

Role Name and Position title Signature Date

Project Director Shawn Butters, Director Kilter Rural

Project Manager David Heislers, Sustainability & Natural Resources Analyst Kilter Rural

26/02/16

Project Outline VERSION CONTROL REVISION HISTORY

Version Date revised

Main Revisions

V0.1 Nov 2015 Internal draft

V1.0 Feb 2016 Final

This document is a managed document and the Project Manager is responsible for its development and maintenance. For identification of substantive amendments each page contains a version number and a page number. Please refer to the Version Control Identification Table for sequence of version numbers.

This project is supported by the Action on the Ground Program funded by the Australian Governmen

Project Outcome AOTGR1-167

Contents

Acknowledgments Abbreviations Executive Summary 1

1. About this document 2

2. About the Project 3

2.1 Objectives 3

2.2 Background 3

3. Description of the landscape 11

3.1 Physical setting 11

3.2 Paddock histories 14

4. Trial paddock operations 16

4.1 Ancillary data collection 16

4.2 Grazing paddock management 20

4.3 Biodiversity paddock management 21

5. The sampling and analysis program 23

5.1 Method and protocols 23

5.2 Spring 2012 survey 24

5.3 Spring 2014 survey 25

5.4 Winter 2015 survey 26

6. Paddock soil carbon stocks 27

6.1 Data analysis 27

6.2 Baseline soil carbon stocks 27

6.3 Stock change 28

6.4 Discussion 30

7. Grazing loads and emissions 32

8. Conclusion 34

References 35


Acknowledgments

This project was supported by funding from the Australian Government through the Carbon Farming Initiative.

Kilter was the lead partner in this project. Sunraysia Environmental coordinated the sampling and analysis program. Bright Futures was the sheep grazier who also maintained grazing records and documented paddock observations during the project. The North Central CMA provided communications and extension support, including the online presence of the project. The University of Melbourne supported with technical advice and peer review.

In-kind support for this project included the provision of trial areas by VicSuper P/L.

This project was also supported input of members of the community who live within or near the project area. In particular they provided input into documenting the history of the trial paddocks.


Abbreviations

AOTG Action on the Ground

DAFF (Commonwealth) Department of Agriculture, Forestry and Fisheries

DAg (Commonwealth) Department of Agriculture

DoA Deed of Agreement

DSE Dry Sheep Equivalent

FFL Future Farming Landscapes

FOSC ‘5-on-7 Country’, a 1250 ha grazing block in the FFL project

GD Grazing Days (cumulative daily head of sheep grazed in paddock)

LSD Least Significant Difference (in statistics)

IC Inorganic Carbon

MDB Murray Darling Basin

OC Organic Carbon

PPA Pest Plants and Animals

TC Total Carbon (IC plus OC)

VES VicSuper Ecosystem Services P/L

1


Executive Summary

AOTGR1-167 was granted project status in Rd 1 of the Commonwealth Action on the Ground program in June 2012. The project area is 150km to the NNW of Bendigo – on the Lower Loddon and Avoca floodplains between Kerang and Lake Boga – where Kilter manages 9,000 ha of semi-contiguous rural property (around 40 individual farming properties).

The context of this project is an important one as it is reflective of the shift from historic broad scale flood irrigation in the southern Murray Darling Basin (MDB) to a more balanced agricultural landscape with modern efficient irrigation and renewed dryland agriculture where irrigation infrastructure has been retired. The project focused on the renewed dryland component, so demonstrating soil carbon impacts in land use change from flood irrigation to (i) low-impact controlled grazing, and (ii) protected biodiversity. The key premise of the project is that the return of permanent groundcover to the landscape should result in more perennial biomass, less cultivation; and therefore the gradual increase in organic carbon incorporated into the soil.

Nine trial paddocks were selected representing four treatment types; grazing or biodiversity and whether these had been actively revegetated or not. Each of the grazing treatment combinations had three replicates. The trial paddocks mostly vary between 30 and 60ha, on grey and brown cracking clays (Vertosols) on the lower and upper floodplain terraces of a riverine landscape. All paddocks have been previously flood irrigated during the 100 year irrigation history of the region.

In the timeframe of this project, especially in a circumstance of low net soil carbon accumulation rates in in a low soil carbon environment, it was not possible to demonstrate a statistically significant change in soil carbon levels under the tested land use scenarios. There were both upwards and downwards fluctuation in soil carbon stocks at the paddock level that were largely within the range of seasonal variations demonstrated in other comparable soil carbon studies. When all data are grouped soil the average total carbon (TC) stock fell slightly, but not statistically significantly, over the course of the 3 year project. This was against the project proposition of achieving a soil carbon stock increase of 6 Mg C/ha over the same period.

The pattern of both soil carbon distribution, magnitude and change appears complex and variable. The nuances in landscape position and the individual management histories of paddocks would be assumed to be strong drivers in the magnitude of soil carbon though these effects cannot be easily differentiated. Overlaying this is the impact of seasonal variation in climatic factors and its impact on plant biomass productivity that was strongly evident in data collected during the project.

This project revealed particular lessons in soil carbon measurement, from ensuring the suitability of sampling conditions (soil moisture) in collecting soil cores; to the question of adequately dealing with the inorganic carbon component of alkaline subsoils.

This project has demonstrated that a multi-decadal approach is likely required to statistically determine soil carbon changes in dry, semi-arid (<350 mm) environments. This will require significant discipline to maintaining appropriate paddock management practices and monitoring over long periods. Such commitment will be further tested in a drying climate with the anticipation of reduced effective rainfall for vegetation growth. Successfully entry of like projects into the carbon marketplace will require application of cost efficient, accurate and repeatable measurement methodologies to offset the low accumulation rates of soil carbon.

2


1. About this document

This document provides a final statement of outcomes for Project AOTGR1-167 and discussion of such. It heavily references (but not repeat verbatim) information from a range of supporting technical and extension documents published during the course of the project:

Technical Report series

TR1: Kilter, 2013. Monitoring and data Protocols. Tech Rpt no. 1 for AOTGR1-167.

TR2: Sunraysia Environmental, 2013. Soil, site and landform description. Tech Rpt no. 2 for AOTGR1-167.

TR3: Sunraysia Environmental, 2013. Spring 2012 soil carbon survey. Tech Rpt no. 3 for AOTGR1-167.

TR4: Kilter, 2013.Trial paddock histories. Tech Rpt no. 4 for AOTGR1-167.

TR5: Waddell G. and Just K., 2014. Baseline paddock vegetation survey. Tech Rpt no. 5 for AOTGR1-167.

TR6: Waddell G. and Just K., 2015. Trial paddock vegetation reassessment. Tech Rpt no. 6 for AOTGR1-167.

TR7: Sunraysia Environmental, 2015. Final soil carbon survey. Tech Rpt no. 7 for AOTGR1-167.

TR8: Kilter, 2016. Trial paddock management. Tech Rpt no. 8 for AOTGR1-167.

TR9: Kilter, 2016. Project outcome. Tech Rpt no. 9 for AOTGR1-167.

Technical Note series

TN1: Kilter, 2015. Baseline survey statistical implications. Tech Note no. 1 for AOTGR1-167.

TN2: Kilter, 2015. Final sampling repeat. Tech Note no. 2 for AOTGR1-167.

TN3: Kilter, 2016. Analysis of soil carbon change. Tech Note no. 2 for AOTGR1-167.

Fact Sheet series

FS1: Kilter, 2012. About the project. Fact Sheet no. 1. for AOTGR1-167.

FS2: Kilter, 2013. About the landscape. Fact Sheet no. 2. for AOTGR1-167.

FS3: Kilter, 2014. Environmental dryland grazing and carbon. Fact Sheet no. 3. for AOTGR1-167.

FS4: Kilter, 2015. Paddock vegetation and soil carbon. Fact Sheet no. 4. for AOTGR1-167.

FS5: Kilter, 2016. Final project results. Fact Sheet no. 5. for AOTGR1-167.

Peer Reviewed Paper

Kilter, 2016. Building soil carbon in semi-arid drylands for landscape resilience.

All documents are available for download from the project web page: http://www.nccma.vic.gov.au/Land/Dryland/BoostingSoilCarbonKilter/index.aspx

http://www.nccma.vic.gov.au/Land/Dryland/BoostingSoilCarbonKilter/index.aspx

3


2. About the project

2.1 Objectives

AOTGR1-167 titled Sequestering Soil Carbon in an Irrigated Landscape turned Dry Ecological Grazing was granted project status in Rd 1 of the Commonwealth Action on the Ground program in June 2012.

The project is argued to be significant because it is reflective of the shift from historic broad scale flood irrigation in the southern Murray Darling Basin (MDB) to a more balanced agricultural landscape with modern efficient irrigation and renewed dryland. This project focusses on the renewed dryland component, in this project being land use change from flood irrigation to low-impact grazing and protected biodiversity.

2.2 Background

2.2.1 Action on the Ground

AOTGR1-167 was funded through round one (2011–12) of the Carbon Farming Futures – Action on the Ground program, administered by the Australian Government Department of Agriculture (DAg) and formerly the Department of Agriculture, Fisheries and Forestry (DAFF). This program was rolled out under the Australian Government’s Carbon Farming Futures initiative under its Securing a Clean Energy Future plan released in July 2011.

4


2.2.2 Project structure

Key participants in the project and the relationships between them are identified in the organisational chart, Fig. 2.1.

Figure 2.1: Organisation chart for AOTGR1-167

Kilter was the grantee (contracted delivery partner) in the Deed of Agreement (DoA) with the Commonwealth. It project managed, reported, undertook or sub-contracted product development (technical and extension) in the project. The primary project partners to Kilter were Sunraysia Environmental (technical services, especially soils and landform mapping), NCCMA (project communications) and Bright Futures (grazier).

Sunraysia Environmental further sub-contracted soil sampling and laboratory services. These services were easily the largest single expense in the project. Kilter procured further services for native vegetation assessment.

Technical review in the project was undertaken by the University of Melbourne (Tom Baker and Chris Weston, School of Ecosystem and Forest Sciences).

5


2.2.3 Physical setting

AOTGR1-167 aimed to demonstrate the sequestration of carbon in soil through trialling a range of land management practices centred on the conversion from flood irrigated cropping to dryland grazing and protected biodiversity. The project area was 150km to the NNW of Bendigo – on the Lower Loddon and Avoca floodplains between Kerang and Lake Boga – where Kilter manages 9,000ha of semi-contiguous rural property (around 40 individual farming properties) on behalf of VicSuper.

Figure 2.2: Project area location (and inset)

The key premise of the project was that the return of permanent groundcover to the landscape – being managed for controlled grazing and protected biodiversity operation – would result in increased biomass and subsequently enhanced opportunity for decomposing plant matter, and therefore increased sequestration of carbon in the soil. The cessation of cultivation would also lead to improved retention of carbon in the soil. The assumption is that over time the former land use land (flood irrigated annual pasture and cropping) has degraded levels of carbon.

An ecological cell grazing joint venture (Kilter and Bright Futures) was introduced FFL and the project area in mid-2012. Its aim was to generate productive value off new dry ground, but in a way to maintain and build a diverse, native groundcover. This would involve short rotations of stock through paddocks and ultimately managing these rotations to support the regenerative capacity of native forage species. Active restoration of the vegetative cover (primarily grassy chenopods) has occurred on some grazing paddocks as well on some biodiversity lands (including paddocks in this project).

On the basis of historical soil surveys organic carbon content across the project landscape is typically less than 1.5% (of soil mass). However the cracking floodplain clays (vertosols) that define much of region’s soils are believed to offer good potential for soil carbon storage. This is in part because of slower rates of carbon depletion generally through clays; but also because of enhanced opportunity for vertical downwards migration of carbon to more protected, deeper parts of the soil profile by virtue of shrink–swell behaviour (ENRC, 2010).

6


The return of carbon to soil is typically a slow process, more so where vegetation production rates are low. Typically, carbon restoration rates of 0.02 to 0.2% per year have been observed in Victorian soils (ENRC, 2010). In the multi decadal timeframe longer term it is hoped that at least a 1% (by soil mass) increase soil carbon levels can be achieved in the project landscape. In the timeframe of this project it was hoped that a soil carbon increase of 0.1% could be achieved, this translating to an increase of 4 tC/ha in the top 30cm of soil (assuming typical soil bulk densities).

2.2.4 The trial paddocks

Nine trial paddocks were selected representing four treatment scenarios, these being grazing or biodiversity and whether these had been actively revegetated or not (Fig. 2.1, Table 2.1). Where possible three replicates were selected for each treatment, though this was only achieved for the grazing scenarios. The trial paddocks mostly vary between 30 and 60ha.

Figure 2.3: Relative location of trial paddocks, Project AOTGR1-167

7


Table 2.1: Trial paddock treatments

Paddock Treatment Types No. Replicates

1 Flood irrigation to ‘passively restored’ rotational grazing

Paddock recovered through rest and PPA control

3

2 Flood irrigation to ‘actively restored’ grazing

Paddock recovery assisted by direct seeding of native grasses and/or chenopods; as well as PPA control

This activity undertaken in 2010 or prior (two years before initial soil survey) with significant visual and/or measurable success

3

3 Flood irrigation to ‘passively restored’ biodiversity

Biodiversity value has recovered through stock exclusion and PPA control

2

4 Flood irrigation to ‘actively restored’ biodiversity

Paddock recovery assisted by direct seeding of native grasses and/or chenopods; as well as PPA control

This activity undertaken in 2010 or prior (two years before initial soil survey) with significant visual and/or measurable success

1

The core of this trial area on the ‘5-on-7’ grazing-biodiversity block (also denoted as FOSC) to the west of Lake Tutchewop, some 5–10km SE of Lake Boga. All (3) of the passively restored grazing paddocks lie on this block in addition to a passively restored biodiversity paddock.

All paddocks are located on variations of grey and brown cracking clays (vertosols) on the lower and upper floodplain terraces of a riverine landscape. All paddocks have been previously flood irrigated during the 100 year irrigation history of the region.

In addition to the nine trial paddocks, two reference areas were selected for the baseline survey. This was aimed to better understand what ‘end member’ soil carbon characteristics might be.

The Mystic Park Bushland Reserve, to characterise what soil carbon levels might be in a relatively natural undisturbed area

Paddock RFBJ2, to characterise what ‘base’ soil carbon levels might look like in a recent flood irrigation paddock (most trial paddocks have not been irrigated for a decade or longer)

More detailed setup characteristics of the trial paddocks are summarised in Table 2.2.

10


Table 2.2: Characteristics of project trial paddocks

Paddock ID

Address Area (ha)

Land Use Treatment Characteristics of Treatment/Comment

FOSC2.1

Murray Valley Highway, Tresco

38 Grazing with passive restoration

First sheep introduced to paddock in Spring 2012. Rotational sheep grazing throughout year. Date, duration and number of stock in paddock determined by grazier under sustainable management principles.

FOSC3.2 Cook Road, Tresco 48 Grazing with passive restoration

First sheep introduced to paddock in May 2012. Rotational sheep grazing throughout year. Date, duration and number of stock in paddock to be determined by grazier under sustainable management principles.

FOSC4.2 Murray Valley Highway, Tresco

33 Grazing with passive restoration

As above, except sheep introduced to this paddock in July 2012.

FOSC7 Benjeroop–Tresco Road, Tresco

34 Protected biodiversity with passive restoration

Area fenced from stock in Autumn 2012. Passive restoration. Project trial area is outside registered BushTender zone.

FPAG10 Vains Road, Fish Point 2.3 Protected biodiversity with active restoration

Area fenced from stock over Summer 2008–09. Active restoration with air broadcast direct seeding took place in April 2010

GMCO7 Rob Roy Road, Fish Point

60 Grazing with active restoration

Mechanical air and manual broadcast seeding from the rear of a utility in the period April to June 2010. First sheep introduced to paddock in Spring 2012. Rotational sheep grazing through year. Date, duration and number of stock in paddock to be determined by grazier under sustainable management principles.

GMGP2.1 Winlaton Road, Fish Point


Paddock direct seeded April 2010 using a mixture of native and introduced species. First sheep entered paddock Winter 2012. Rotational sheep grazing through year. Date, duration and number of stock in paddock to be determined by grazier under sustainable management principles.

JCRO2 Three Chain Road, Tutchewop


Direct seeding carried out March 2010 (with Kilter seeder) and April 2010 (air broadcast method). First sheep introduced to paddock in August (Spring) 2012. Rotational sheep grazing through year. Date, duration and number of stock in paddock to be determined by grazier under sustainable management principles.

KCLO3 Flood Lane, Lake Charm

28 Protected biodiversity with passive restoration

Area fenced from stock in 2012. Passive restoration.

11


3. Description of the landscape

3.1 Physical Setting

Report TR2 documents in detail the regional physical and climatic context for the project.

3.1.1 Landform and Soils

The project area lies right at the overlap of a mature riverine landscape (of the lower Loddon and Avoca valleys) with the eastern margin of the Mallee dune country, the latter exhibited by the horticultural dune scape of Tresco. The current active floodplain is of very low gradient and generally less than 5 km wide. In the project area the Loddon River flows into the Little Murray River (near Fish Point), that is a regulated anabranch of the Murray River (the area lies within the Torrumbarry Irrigated District). The project area contains a number of fresh (now regulated and permanent) and salt lakes with well-developed single or multi-crested lunette systems on their eastern margins. Additional minor relief offered by a number of ‘sand rises’ that have windblown over the main underlying riverine morphology.

Detailed though incomplete soils mapping by the Victorian Department of Agriculture occurred across the project landscape in the1960s (Figure 3.1). Although not previously mapped in detail, two key classes of soils area are present. Uniform grey and brown cracking clays (or Vertosols) predominate, these characteristically shrinking (in summer) and swelling (in winter). This gives rise to seasonal vertical movement of soil particles in the profile, typically resulting in a ‘mulch’ of loose aggregates at the surface. The more elevated ground tends to be occupied by vertically contrasting red soils but with a clayey subsoil (Sodosols) and with local build-up of carbonate rich layers.

The soils of the trial sites primarily comprise the following mapped associations:

Della Clay. A grey, cracking clay which becomes yellowish or brownish, and slightly calcareous between 10 and 33 cm, the soil type of the almost level plains of the Black Box woodlands. This unit encompasses the FOSC grazing block. Most areas of Della clay are either saline or potentially saline.

Boga Clay Loam. A grey saline soil type occupying broad, shallow depressions and low plain in the mallee plain landscape unit which occurs extensively in the Mystic Park area. The original vegetation was predominantly mallee with Black Box a minor component.

Donnington Clay. Although the area was not originally mapped, the soils of the trial sites at or near Fish Point (NE of Lake Boga) are characteristic of this Donnington Clay association.

Low topographic grades, together with low permeability soils and floodplain silts across the region, result in both sluggish surface and groundwater drainage, predisposing the region to land salinisation risk. Salt is natural to this landscape, but human activity has altered the water balance to build excess concentrations of salt in the plant root zone.

The currently active floodplain (at least prior to human intervention) has likely the highest potential for soil carbon storage As the older, higher and drier floodplain terrace is stranded from moisture resources it is more quickly exhausted of carbon and nutrients.

12


Figure 3.1 Historical soils mapping of the Swan Hill area

13


3.1.2 Climate and Vegetation

The project area lies in northern Victoria and experiences a temperate, semi-arid climate. Summers are typically hot and dry under high pressure, occasionally punctuated by tropical airstreams with storm rainfall. Winters are cool and damp, being impacted by frontal systems of the westerly wind belt. Annual rainfall averages around 350mm/yr and with a slight winter-spring bias, though is highly variable.

Although now extensively cleared and modified, the remnant indigenous vegetation comprises variants of grassy box woodlands of the Murray Fans and Victorian Riverina bioregions. Only scattered remnant vegetation occurring on roadsides and within private blocks. Remnants largely occur on (i) the higher alluvial terraces of the Murray River and would originally have been dominated by Black Box woodlands (EVC Riverine Chenopod Woodland and Plains Woodland) and low chenopod shrublands (EVC Chenopod Grassland), with (ii) low lying areas closer to the river supporting River Red Gum forests (EVC Riverine Grassy Woodland). A series of rises occur throughout the area that are aeolian deposits from nearby lakes. These would probably once have supported Cypress-pine woodlands (EVC Semi-arid Chenopod Woodland) but all examples have long been cleared.

14


3.2 Paddock histories

Report TR4 documents in detail the land management histories of the trial paddocks.

3.2.1 General

The explorer Major Thomas Mitchell first passed through the landscape in 1836 and remarked on the abundance of grass but the absence of trees along the banks of the Little Murray River. He wrote of the Murray Pine he saw on the landscape undulations (the lunettes).

The black and grey cracking clays of the lower Loddon floodplain and lighter onlapping dune country were first developed for irrigation in the late 1890s. However soil salinisation processes were evident early, with the relatively shallow and naturally saline watertables quickly topped-up through accessions from irrigation. With production stifled by salinity and soil degradation the irrigation intensity steadily declined across the landscape during the course of the 1900s and became largely confined to early season watering of winter pastures (dairy) and crops. By 2000 the ‘millennium drought’ had hit and heralded a period of generational change in irrigation distribution and practice.

The Tutchewop Plains

The ‘5-On-7’ grazing and biodiversity block - incorporating 4 trial paddocks - sits on what was known as the Tutchewop Plains to the south and east of the Tresco horticultural ridge. The plains were heavily covered in grey box timber before being cleared for irrigation from the 1910s. Early agricultural production ranged from flood irrigated fodder crops to pastures for dairying, wool and fat lambs. Top quality Lucerne was also grown. However within a decade of development there were production impacts from soil salinity through excessive watering of the plains and adjacent horticultural ridge. Large areas of citrus died out at the base of the Tresco ridge with the impacts progressively extending outward onto the plain. Drought and plague rabbits made farming difficult for many years until the early 1950s. Top quality Lucerne was planted again during the 1960s following cessation in operation of many of the original dairy farms.

15


By the end of the first decade of the new millenium - at the end of crippling drought - the once generous water rights of the 5-on-7 block had been removed as part of an irrigation modernisation land buy-back scheme. Upon purchase by VicSuper, reconfiguration of the 5-on-7 country (FOSC) occurred in Autumn 2012 with fencing and establishment of a piped stock and domestic water supply. 24 grazing cells were established (varying in area between 30 and 50ha) with Merino wool lambs introduced onto the block in late May 2012.

The Winlaton District

The Winlaton District was part of the original Murrabit Station (circa 1850s) that occupied about 10,000ha of country between Lake Boga and east to the Loddon River. This area included the project trial paddocks at Fish Pt (FPAG10, GMGP, GMCO7) and JCRO2 further SE. The original station in fact ran Lincoln/Merino ewes and Southdown sheep.

Irrigation in the Winlaton area was introduced in the early 1890s; with the first land watered between Lake Tutchewop and the Loddon River (comprising what became known as the Winlaton Estate). Water was pumped from Lake Tutchewop – that at the time was a fresh, ephemeral wetland – to irrigate pastures, oats and barley. The landscape was sparsely timbered with Murray Pine, Hakea, Sandalwood, Cattle Bush and clumps of Box (Eucalyptus spp.) on lower ground. During floods, lakes, creeks and swamps would overflow and inundate farm land.

With building of levees, irrigation infrastructure and regulation of the lake system the Winlaton floodplain has become largely stranded from the river, with even large floods (such as 2011) struggling to break levees. Nevertheless the ‘Winlaton Depression’ carried’ water for the first time in 100 years with the flood of January 2011.

Similarly to the Tutchewop Plains drought and water scarcity from the mid-1990s has seen a dramatic change in agriculture at Winlaton, with a long tradition of dairying on irrigated annual pasture almost entirely disappearing from the landscape. Prior to the purchase of properties in the district by VicSuper (2006-09), agricultural activity on many these had stagnated.

16


4. Trial paddock operations

4.1 Ancillary data collection

A number of datasets were collected during the course of the project that provided at the very least provided important context or were of direct relevance to interpretation of the soil carbon data.

4.1.1 Grazing data

Through the life of the project joint venture grazier Bright Futures P/L contributed paddock grazing records for the project. This occurred on a regular 6-monthly basis and were compiled into an Excel spreadsheet to the calculation of grazing loads (including conversion to dry sheep equivalents, or DSE) and equivalent greenhouse gas emissions.

The grazier maintained a diary of grazing activity that comprised the nos. of ewes and/or lambs on any one paddock on and day of the year. This was translated into a spreadsheet from which a number of quantities were calculated. In the first instance a month quantity ‘Grazing Days’ (or GD) was calculated by adding the daily head of sheep on the paddock, this separately for ewes and weaned lambs.

To better reflect feed load on the paddocks GD was converted to ‘DSE Grazing Days’ (DSE GD) accounting for feed demand of the year round lambing cycle. This necessitated the attribution of a DSE rating (DPI, 1997) during the lambing cycle, this attributed on a monthly basis as indicated in Table 4.1. These ratings were determined by advice from the grazier. The annual cycle reflects that, on average, ewes were joined in mid-autumn with lambs born late winter. Lambs were generally weaned in the 2nd half of September.

Table 4.1: Monthly DSE attribution

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Ewes 1.5 1.5 1.5 1.5 1.8 1.8 13.0 13.0 13.0/2.0 1.5 1.5 1.5

Lambs 1.0 21.2 21.2 - - - - - 0.4 0.6 0.8 1.0

1 Ewes with lambs at foot

2 Ewe lambs

From GD DSE the calculation of equivalent CO2-e emissions could be calculated by applying a standard emission factor, 141 kg CO2-e per DSE (White & van Rees, 2011).

17


4.1.2 Climate data

The chief climate variable of interest is rainfall, not just in quantum but how it’s distributed over the year (so in one sense the effectiveness of rainfall). Figure 2.1 illustrates the significant variability from month to month for Lake Boga. As one measure, of the 42 months between Jan-12 and Jun-15, there were 6 (14%) that were either Decile 1 or 10. Though calendar year rainfall for the years 2012-14 was relatively consistent (85%, 91% and 91% of Mean), summer, autumn and winter seasonal totals widely fluctuating over the period. Of all seasons spring rainfall was the most consistent, but significantly below average in each year.

As discussed in Section 3.1 later rainfall variability has had significant implications for the project, from sampling efficacy to grazing management decisions (via vegetation growth and therefore feed availability).

Figure 4.1: Relative location of trial paddocks, Project AOTGR1-167

18


Table 4.2: Proportion of seasonal rainfall achieved

Year Summer Autumn Winter Spring Annual (Cal)

2012 113% 103% 82% 64% 85%

2013 48% 53% 140% 84% 91%

2014 99% 192% 67% 70% 91%

2015 59% 62% 104%

4.1.3 Vegetation data

Method

A baseline vegetation cover and diversity assessment was undertaken across all the trial sites, this was completed in Nov-13 and again in Nov-14 to obtain a sense of variability (same time of year was kept to maximise comparability). The results of this work is described in TR5 & 6, as well as summarised in FS4.

The vegetation of each paddock was sampled using between three and five semi-randomly located 10 x 10m quadrats (these sited to reflect the range of vegetation assemblage). Within each quadrat all vascular plant species were recorded and each lifeform (general vegetation form) assigned a cover value. Cover values were also assigned to bare ground, litter and soil crust. Each quadrat was qualitatively scored on a 1-5 scale on ‘pre-1750 vegetation intactness’ (the Frood Score). Reference photos were taken.

Figure 4.3: Vegetation survey in AOTGR1-167

Reference photo of quadrat 4, paddock FOSC2.1 Comparison of lifeforms evident in all quadrats FOSC2.1 between 2013 and 2014

General observations

Most paddocks were dominated by a high cover (vegetation and litter), they exhibit limited diversity of exotic annual grasses and herbs with scattered chenopod shrubs and occasional Black Box trees. Indigenous ground flora is typically sparse and restricted to species that have managed to re-colonize since the cessation of irrigation or that have been revegetated through direct-seeding. Some paddocks were observed to contain small isolated patches with higher coverage of native

19


grasses and herbs. All paddocks were observed to be in a stage of recovery following a prior history of flood irrigation whereby many of the original indigenous species would have been cleared. Using the Frood Vegetation Condition Score all quadrats in all paddocks excluding one scored Poor (4) or Very Poor (5).

Overall cover of vegetation in each paddock was generally between 50-70%, although some areas of paddocks are as low as 40%. Litter, which also contributes to the carbon cycle by increasing the overall cover of plant material present typically provided around 20-40% of cover (greater in 2014 than 2013).

There was considerable variation in the diversity of species within lifeforms, with the exotic herb and exotic tussock-grass lifeforms generally supporting the highest diversity of species (up to 5-10 per quadrat). The diversity of native lifeforms was highly variable, with the shrub, tussock-grass, prostrate shrub and herb lifeforms either being absent or supporting from one to five species. The exotic shrub, exotic geophyte, geophyte, scrambler/climber and sedge/rush lifeforms were absent from large parts of the study area, with only one to several species occurring in some sites.

The vegetation biomass is likely to vary throughout the year across the study area due to the dominance of exotic annuals. The paddocks would have the highest biomass during the peak growth stage in winter-early-spring, followed by a rapid drying and desiccation of vegetation over the summer period. Biomass is also likely to vary seasonally due to differing rainfall patterns and grazing regimes. The paddocks would likely have a more even biomass level throughout the seasons if they supported a higher cover of both winter active (C3) and summer active (C4) native perennials.

The cover and diversity of most lifeforms was generally lower in 2014 than 2013, put down to low rainfall in the preceding months. Many species would also have produced low amounts of seed in 2013 due to the below average rainfall throughout some of the winter and spring months. It is difficult to detect patterns in the species that appeared or disappeared within quadrats across the two years, however it was the annual herbs and grasses which tended to show the greatest transience. A notable exception to this pattern was the increase in exotic grass cover at all of the FOSC sites, which could possibly be explained by a positive response of this lifeform to high autumn rains in 2014. At several sites there was a marked increase in litter cover and corresponding decrease in bare ground. This is likely attributable to the vigorous growth of exotic annual grasses in 2013 and the exclusion of stock since that time, allowing grass to break down into litter.

4.1.4 Photopoints

All trial paddocks were visually captured with 6 monthly repeated photography over the duration of the project. This was from designated photopoints, or common points of capture. Many of the points selected are part of the ongoing FFL landscape monitoring program. Photopoints were reshot each November and May during the survey window. This visual documentation is presented fully in TR8, an example of such in Figure 4.4 for site FOSC4.2 below.

20


Figure 4.4: Photopoint illustrating year to year seasonal variability (trial paddock FOSC4.2)

May 2013 3 month lead-up rainfall: 31mm



4.2 Grazing paddock management

4.2.1 The grazing enterprise

During the time of the project Kilter Rural and Bright Futures were engaged in a joint venture wool and fat lamb enterprise within a time-controlled cell grazing model, in a broadly holistic approach. This was established in the first half of 2012 with breeding ewes introduced in the landscape by May. As at the end of July 2015 (month the final sampling) the flock had grown to 2720 ewes from 1280 ewes at the project start in July 2012.

Since its inception the grazing enterprise has been an adaptive one, with stocking rates and movements determined by observation paddock carrying capacity and plant response. The intent is to manage grazing movements to balance between the growth of winter (C3) and summer active (C4) native grasses and in the process contain the proliferation of annual exotics. Seasonal topping-up of feed (including for nutritional benefits) would be strategically enabled through stock access to post-crop stubble and lucerne, but also potentially for strategic weed control in agroforestry and biodiversity zones.

The enterprise is dually focused on incrementally lifting ecological values and paddock stocking rates over the next decade and sustainably maintaining these.

Figure 4.5: Grazing layout on the ‘5-on-7’ grazing-biodiversity block

Grazing cell layout and biolink (green) on the ‘5-on-7’ block, the core of Pj. AOTGR1-167

Sheep being rotationally grazed in the project area (2012)

21


4.2.2 Adaptive grazing management during the trial

The grazing enterprise operates on a true commercial basis embedded within a whole of landscape approach to generating sustainable commercial returns from the broader FFL investment. In this context there were several factors that influenced how the landscape was grazed during the course of the project that did influence grazing loads. Such factors included:

In 2013-14 the opportunity to graze new lucerne paddocks and corn stubbles became a valuable feed opportunity, so leaving grazing paddocks being understocked at times through this period

Grazing loads were strategically reduced during 2014 as a measure to build vegetative biomass to support grazing in an anticipated El Nino summer (that technically did not eventuate). As a consequence FOSC grazing paddocks were left ungrazed (apart from FOSC4.2) until into early 2015.

By April 2015 trial paddocks FOSC3.2 & 4.2 were removed from the active grazing prior owing to a planned transition into sub-surface drip irrigation development. A robust business case had been established to justify a shift away from grazing back into irrigation. Being a recent decision this change was immaterial to the AOTG project. Prior to the final sampling there was the removal of internal fences and filling of channels but otherwise no destructive ground disturbance.

4.3 Biodiversity paddock management

Three of the trial paddocks are protected for their biodiversity value. They are fully fenced to exclude stock or to manage stock if they were to be strategically grazed. During the course of the project the general characteristics of their management were:

All were managed for their weed burden (spot and boom spraying depending upon the nature of the infestation)

FOSC7 being a paddock with a BushBroker covenant was under a formal site management plan. In essence this specifies site access conditions (restricted) as well as a requirement to identify and manage weeds

FPAG10 was the only biodiversity paddock subject to any revegetation activity though this activity occurred several years prior to AOTGR1-167

22


Table 4.3: Paddock management summary

Trial Paddock Planned Treatment Treatment Outcome

FOSC2.1 Grazing with passive restoration 12,134 Grazing Days (58 days in paddock). Significant resting in 2014 owing to alternative feed opportunity. Paddock to be retired from grazing post project.

FOSC3.2 Grazing with passive restoration 15,280 Grazing Days (20 days in paddock). Significant resting in 2014 owing to alternative feed opportunity.

FOSC4.2 Grazing with passive restoration 15,350 Grazing Days (151 days in paddock). Significant resting in 2014 owing to alternative feed opportunity. Paddock to be retired from grazing post project.

FOSC7 Protected biodiversity with passive restoration Fully protected (fenced) over period. No stock. Strategic weed control undertaken (boxthorn).

FPAG10 Protected biodiversity with active restoration No stock. Native grass (Danthonia) sward impacted by over-spray from adjacent crop.

GMCO7 Grazing with active restoration 35,635 Grazing Days (183 days in paddock). Significant resting in 2014 owing to alternative feed opportunity.

GMGP2.1 Grazing with active restoration 3,542 Grazing Days (62 days in paddock). Low grazing density initially, then stock removed indefinitely owing to unviable fencing (deemed not commercial to maintain)

JCRO2 Grazing with active restoration 6,360 Grazing Days (23 days in paddock). Significant resting in 2014 owing to alternative feed opportunity.

KCLO3 Protected biodiversity with passive restoration Fully protected (fenced) over period. No stock. Strategic weed control undertaken (flat weeds).

23


5. The sampling and analysis program

Sampling for soil carbon analysis was undertaken in tranches as summarised in the following table.

Table 5.1: Completed schedule of AOTGR1-167 soil carbon survey

Date Scope

2012, November Baseline survey

9 trial paddocks and 2 additional reference sites (18 samples each paddock/site)

General soil analytes in addition to organic soil carbon and bulk density

2014, October

9 trial paddocks (18 samples each paddock)

Organic soil carbon and bulk density

2015, July

9 trial paddocks (18 samples each paddock)

Organic soil carbon and bulk density

There were significant variations from the original planned schedule.

1. The mid-term survey (planned either spring 2013 or autumn 2014) was abandoned in favour of adding statistical robustness (by increasing sampling intensity) to the final project sampling. The original intent of the mid-term sampling was to assess the impacts of seasonality (either between alternate seasons or from one year to the next) rather that for gross change in carbon stocks. Recognition of this adjustment was made in the Project Plan revision of October 2013. The case for consolidating the final sampling effort was further advanced in TN1 (2015) that summarised the statistical implications of the baseline survey analysis.

2. A full rerun of the October 2014 sampling was undertaken in July 2015. This was due to recognition of significant quality issues in the 2014 data. It was apparent that the dryness of the soil profile in the survey period had resulted in partial disintegration of soil cores during sampling that impacted on the BD measurement and potentially compromising soil OC measurement (refer section 5.3). The resampling and associated time extension for the project was agreed by the Commonwealth.

5.1 Methods and protocols

The soil sampling undertaken in this project were largely consistent with the standards derived by the Soil Carbon Research Programme (SCaRP). The basic standards of ScaRP were adapted to the specific need of AOTG soil carbon projects and set out in sections 9 and 10 of TR1 (2013). These sections cover:

1. In-paddock Sampling Site Selection

2. In-paddock Navigation

3. Soil Coring Method

4. Sample Extraction and Bagging

5. Sample Storage and Transport

24


A departure from the strict SCaRP protocol was that the Dumas furnace method was applied to the untreated samples (ie. samples not pre-treated to remove inorganic carbonate). This as the laboratory’s furnace utilises small foils whereby a sample into compressed into a ball, not lending to the routine addition of reagents/pre-treatments such as acid treatments. Standard practice of the laboratory is for off-line determination of inorganic carbon (IC), with total organic carbon (OC) determined by difference. This solution would potentially allow comparison of OC data (albeit indirectly measured), but also total carbon (TC). An advantage of having directly measured TC data is that it is not impacted by incomplete or ‘over’ dissolution IC (the latter being potentially inflated by acid soluble forms of OC). As this project is essentially about demonstrating change in soil carbon (and this would be reflected in TC) it was felt that this compromise was a reasonable one. It recognises the balance in efficiency and cost economy in soil sampling on the one hand and sufficient technical rigour on the other.

5.2 Spring 2012 surveySelection

The spring 2012 baseline survey was undertaken over a 3 day period in late October. Conditions proved perfect for sampling with ground conditions dry enough for uninhibited site access, yet the soil sufficiently moist for cores to remain intact allowing straight forward extraction. Rainfall in the 3 months leading-up to sampling was about 80% of the long term average.

Eleven paddocks encompassing 4 land-use treatments and 2 reference sites were sampled, with 18 (15 in reference sites) semi-randomised samples taken per paddock. Sampling was completed successfully in relation to the defined technical protocols.

The outcomes of the spring 2012 baseline survey are detailed in TR3 (2013). Results are summarised in section 6.

Figure 5.1: Soil carbon sampling in October 2012

Soil coring in action, October 2012. Splitting of the cores and bagging of samples

25


5.2.1 Statistical implications of baseline survey

TN1 examined statistics of the 2012 sampling results in order to optimise design of the final soil carbon sampling. A key question is whether the final paddock sampling can be optimised to be able to discern a statistically significant change in SOC stock over a 2.5 to 3 year period. Assuming paddocks are resampled at the same intensity the calculation of the statistical term Least Significant Difference (LSD) showed the project’s proposition (of an increase of 6 Mg/ha C over the project life) would likely not be demonstrated statistically.

The sensitivity of this result was further tested with a range of sampling strategies, such as doubling the sampling intensity. The conclusion was that there were only marginal differences in the LSDs arising from the alternatives examined, and no alternative was adequate to statistically discern the project’s proposition change in SOC density. It was then therefore concluded that there was no good reason (especially on cost-benefit terms) to adjust the sampling design to be different from that of the baseline survey.

5.3 Spring 2014 survey

The intended second and final sampling for the project was undertaken over the period 21-23

October 2014. As for the 2012 survey surface ground conditions were excellent for surveying. However upon analysis of the laboratory results it was clear that soil carbon stocks were on average markedly less than in 2012. Closer inspection of the data showed that much of the difference could be explained by the lower bulk density (BD) of the 2014 samples. While not foreseen or recognised as a problem during the sampling, it subsequently became apparent that the dryness of the soil profile to depth had resulted in substantial disintegration of soil cores during sampling. This resulted in re-sorting and loss of soil bulk across the sample depth intervals. Moreover, this would also likely have affected the distribution of soil C concentrations. Figure 5.2 illustrates the contrast in core condition between the 2012 and 2014 surveys. The sampling issue is explored in detail in TN2 (2015).

Figure 5.2: Comparison of soil cores, October 2012 and 2014

Example 2012 core. Note its degree of intactness Example 2014 core. Note the disintegration of the core, largely attributable to the dry soil condition

26


Rainfall in the 3 months leading-up to sampling was about 45% of the long term average, and October itself was a Decile 1 rainfall month. Spring heat was also significantly above average, and together with the rainfall deficiency, clearly supports the occurrence of a very dry soil profile.

5.4 Winter 2015 survey

The rerun of the final sampling survey took place in the last week of July 2015. July was chosen for several reasons, to facilitate final delivery of the project within timeframe (ruling out October) but also because of the impending El Nino summer and therefore the high likelihood of low soil moisture conditions. As it happened the record dry and hot October 2015 would have rendered effective sampling impossible. Near average rainfall (95%) and significantly cooler than average temperatures in the 3 months leading-up to the July survey gave confidence that soil moisture levels would be adequate for core collection – and they were.

The sample effective sampling strategy (including sampling intensity) was adopted for this survey as for 2012, with 18 sites sampling sites per trial paddock. The reference paddocks were not resampled.

The outcomes of the winter 2015 survey are detailed in TR7 (2016).

27


6. Paddock soil carbon stocks

6.1 Data analysis

The results as follows are generally discussed in terms of Total Carbon (TC) stocks in mega grams (Mg) per hectare over the quoted depth interval. Mg/ha is the convention in soil carbon science, but is equivalent to the unity in common usage tonnes (t) per hectare/ha. Carbon stock is a linear function of the (i) concentration by mass and (ii) the bulk density of the sample (over the given depth) that are directly measured laboratory parameters.

Initially an attempt was made to analyse and compare the Organic Carbon (OC), the more conventional measure of soil carbon in usage. However, as discussed in TN3 there were significant data inconsistencies identified in the 10-30cm interval, possibly related to the laboratory treatment of Inorganic Carbon (IC) in this interval. This ultimately led to the use of TC as a more robust soil carbon measure. There was the added confidence in adopting TC as it was measured directly and by a single laboratory process, whereas OC was calculated by difference between independent TC measurements.

Even in the TC data there is some question to the robustness of the 10-30cm subsoil data. There were numerous large changes in the data identified from the 2015 sampling, up to a halving or doubling of the baseline (2012) stocks. These changes do not seem plausible especially given the that subsoil ought be less sensitive to change than the topsoil (0-10cm). This led to a particular focus on the TC 0-10cm data.

Table 6.1: Completed schedule of AOTGR1-167 soil carbon survey

Comparison of the 2012 and 2015 TC stocks for the 9 trial paddocks in the 0-10cm interval. Note the relative small and consistent (in magnitude) stock changes. This dataset was the main basis for conclusion in the project

Comparison of the 2012 and 2015 TC stocks for the 9 trial paddocks in the 10-30cm interval. Note the relatively large and erratic stock changes, that brought into question the robustness of this data

Trial

6.2 Baseline soil carbon stocks

Average baseline (2012) TC stocks across all sampling was 21 Mg C/ha over the 0-10 interval (equivalent to 45% of the 46 Mg C/ha averaged over the full 30 cm sampling depth). There was wide variation from paddock to paddock with TC stocks ranging from13 to 32 Mg C/ha (0-10cm). Generally the lowest TC (<18 Mg C/ha) was observed on the 5-on-7 block trial paddocks on the western side of the Murray Valley Highway. TC stocks >20 Mg C/ha (0-10cm) were generally

28


evident in paddocks closer to the river east of the highway. This tendency in spatial distribution was much more muted in the 10-30cm interval.

Interestingly the reference area of the Mystic Park State Forest, used as a proxy for ‘natural’ soil carbon levels in the general project landscape, averaged only 15 Mg C/ha (0-10cm), no better that the historically irrigated trial paddocks on the 5-on-7 block. The other reference paddock at Benjeroop (RFBJ2), representing the case of very recent flood irrigation, was significantly denuded of TC compared to the other riverside paddocks with a mean of 15 Mg/ha C (0-10cm). This supports the contention of (albeit does not prove) soil carbon loss under practices associated with flood irrigation. Soil carbon levels in this paddock may have influenced by several months of inundation in relation to the record lower Loddon flood January 2011.

6.3 Stock change

Analysis following the Jul-15 sampling showed that TC changed by an average of -0.73 Mg C /Ha (0-10cm interval) when considering all paddock data together. This is equivalent to a reduction of 3.5% on the baseline data. The paddock by paddock variation was -4.2 to + 3.7 Mg C/ha (0-10cm). These variations are within seasonal variations reported elsewhere, but, importantly in the majority of instances are statistically insignificant either on an individual paddock or aggregated basis.

This statistical insignificance can be appreciated by observing the relative comparability in the magnitude of the TC changes with the standard deviation of the data (Table 6.2). Further, the Least Significant Difference (LSD, and assuming a p-value of 0.05) on all the TC 0-10cm data was determined to be 2.97 Mg C/ha. Nearly all measured change at the aggregated or paddock level TC 0-10cm data was less than this value so confirming statistical insignificance.

The only appropriate case of aggregating to the land-use scenario level could be considered for the passive restored grazing category, where there were 3 paddocks within relative proximity and similar land use histories. In this instance the average change was a statistically insignificant -1.51 Mg TC/ha (-9.6% change) in the 0-10cm interval.

Though there is some question as to the reliability of the OC data (discussed above) a change of +0.07 tC/ha (+0.4%) was seen in the 0-10cm interval, a similarly statistically insignificant result.

As indicated above stocks and change reported in the 10-30cm interval are dubious. At the paddock level there were changes (gains and losses) of between 10 and 20 Mg C/ha (as TC) observed in 4 of the 9 trial paddocks, amounting to as much as a half or doubling of baseline levels.

29


Table 6.2: Total Carbon (TC) stocks

Paddock Treatment Interval (cm)

2012 Stock (Mg C/ha)

Std Dev

Coef of Var


Std Dev

Coef of Var

Stock Change (Mg C/ha)

% Change

FOSC2.1

Passive grazing

0-10 15.31 4.3 28% 15.05 3.9 26% -0.26 -1.7%

10-30 20.81 6.0 29% 31.20 11.6 37% 10.39 49.9%

0-30 36.12 7.0 19% 46.25 10.8 23% 10.13 28%

FOSC3.2

Passive grazing

0-10 18.34 5.2 28% 14.13 2.6 19% -4.21 -23.0%

10-30 24.90 8.7 35% 26.72 6.9 26% 1.82 7.3%

0-30 43.24 11.1 26% 40.85 6.3 15% -2.39 -5.5%

FOSC4.2

Passive grazing

0-10 13.59 2.2 16% 13.54 3.7 27% -0.06 -0.4%

10-30 12.90 3.1 24% 23.76 13.4 56% 10.86 84.2%

0-30 26.49 4.4 17% 37.30 14.1 38% 10.80 40.8%

FOSC7

Passive biodiversity

0-10 15.96 3.3 21% 16.07 3.5 22% 0.10 0.6%

10-30 26.03 8.4 32% 31.63 8.0 25% 5.60 21.5%

0-30 41.99 7.9 19% 47.70 7.8 16% 5.71 13.6%

FPAG10

Active biodiversity

0-10 29.85 7.2 24% 27.64 4.1 15% -2.21 -7.4%

10-30 44.33 6.9 16% 29.23 6.7 23% -15.11 -34.1%

0-30 74.18 11.1 15% 56.87 8.4 15% -17.31 -23.3%

GMCO7

Active grazing

0-10 23.51 6.4 27% 25.35 6.6 26% 1.85 7.9%

10-30 20.59 3.7 18% 19.32 4.6 24% -1.27 -6.2%

0-30 44.10 7.8 18% 44.67 9.4 21% 0.58 1.3%

GMGP2.1

Active grazing

0-10 28.34 5.8 21% 31.99 6.0 19% 3.65 12.9%

10-30 25.67 4.4 17% 27.14 5.7 21% 1.48 5.7%

0-30 54.01 8.2 15% 59.13 8.1 14% 5.13 9.5%

JCRO2

Active grazing

0-10 17.79 3.6 20% 15.67 2.9 19% -2.13 -12.0%

10-30 31.58 6.7 21% 13.84 3.2 23% -17.74 -56.2%

0-30 49.37 8.8 18% 29.51 5.0 17% -19.87 -40.2

KLCO3


0-10 25.60 5.6 22% 22.31 4.0 18% -3.29 -12.8%

10-30 21.48 3.4 16% 19.26 4.5 23% -2.23 -10.4%

0-30 47.08 7.2 15% 41.57 6.7 16% -5.52 -11.7%

All trial paddocks

0-10 20.92 7.5 36% 20.19 7.7 38% -0.73 -3.5%

10-30 25.37 10.2 40% 24.68 9.6 39% -0.69 -2.7%

0-30 46.29 14.9 32% 44.87 12.3 27% -1.42 -3.1%

Passive grazing paddocks

0-10 15.75 4.5 28% 14.24 3.4 24% -1.51 -9.6%

10-30 19.54 8.0 41% 27.23 11.2 41% 7.69 39.4%

0-30 35.29 10.5 30% 41.46 11.3 27% 6.18 17.5%

Mystic Park

Reference paddock

0-10 14.72 3.3 23% n/a n/a

10-30 23.72 9.0 38% n/a n/a

0-30 38.44 10.9 28% n/a n/a

Benjeroop Reference paddock

0-10 15.20 3.5 23% n/a n/a

10-30 14.92 6.9 47% n/a n/a

0-30 30.12 8.0 27% n/a n/a

30


Table 6.3: Organic Carbon (OC) stocks, 0-10cm interval

Paddock Treatment Interval (cm)


Std Dev

Coef of Var


Std Dev

Coef of Var

Stock Change (Mg C/ha)

% Change

FOSC2.1

Passive grazing

0-10 13.42 5.9 44% 14.03 4.9 35% 0.61 4.5%

FOSC3.2

Passive grazing

0-10 15.77 6.9 44% 12.63 5.0 40% -3.14 -19.9%

FOSC4.2

Passive grazing

0-10 11.08 4.9 44% 11.02 4.3 39% -0.06 -0.6%

FOSC7


0-10 11.86 6.2 52% 14.34 5.3 37% 2.48 20.9%

FPAG10

Active biodiversity

0-10 29.85 7.2 24% 27.64 4.1 15% -2.21 -7.4%

GMCO7

Active grazing

0-10 22.56 6.5 29% 25.35 6.6 26% 2.79 12.4%

GMGP2.1

Active grazing

0-10 28.34 5.8 21% 31.99 6.0 19% 3.65 12.9%

JCRO2

Active grazing

0-10 15.64 3.8 24% 15.48 3.5 23% -0.16 -1.0%

KLCO3


0-10 25.60 5.6 22% 22.31 4.0 18% -3.29 -12.8%

All trial paddocks

0-10 19.35 8.6 45% 19.42 8.6 44% 0.07 0.4%

Passive grazing paddocks

0-10 13.43 6.2 46% 12.56 4.8 38% -0.86 6.4%

Mystic Park

Reference paddock

0-10 13.72 4.7 34% n/a n/a

Benjeroop Reference paddock

0-10 14.97 3.3 22% n/a n/a

6.4 Discussion

In the timeframe of this project, and especially in a circumstance of low accumulation rates in an inherently low soil carbon environment, it was not possible to demonstrate a statistically significant increase in soil carbon levels under the tested land use change scenarios between 2012 and 2015. This conclusion held for both individual paddocks, where paddocks could be reasonably grouped with like land-use and fully aggregated data.

The pattern of soil carbon distribution, its magnitude and change appears complex and variable. The nuances in landscape position and the individual management histories of paddocks would be assumed to be strong drivers in the magnitude of soil carbon though these effects cannot be easily differentiated. This complexity is exemplified in one of the two additional reference areas sampled. Though an obvious area of natural (though modified) remnant vegetation and therefore presumed reasonably intact natural levels of soil carbon, the average TC stock in the Mystic Park State Forest was no more than the historically irrigated paddocks on the 5-on-7 block to the north.

Given the general statistical insignificance of the soil carbon changes in individual trial paddocks as well as the aggregated data (as exemplified in the 0-10 cm TC and OC data) there is little knowledge that can be drawn yet from impacts from change to dry land-uses. It is possible that sequestration of soil carbon over the project period was inhibited by drier than average conditions over the 36 months to Jul-15 (there was a 12% deficit from average rainfall over the period).

31


Seasonal variability of environmental conditions was significant during the course of the project that would tend to mask any underlying long term change. This variability, largely reflected in rainfall patterns, was very evident in the paddock photo records that are fully documented in TR8. The photo record example in Fig. 4.4 illustrates the strong contrast in plant biomass in the May-12, 13 and 14. Seasonal variation was also reflected in the vegetation lifeform and diversity surveys of 2013 and 2014 (TR 6), characterised by a significant decrease in plant diversity as well as a significant increase of litter coverage (less bare ground) over successive years.

32


7. Grazing loads and emissions

As indicated in 4.2.2 paddock grazing was managed conservatively during the period of the project, reflecting:

Feed constraints at time of grazing

Assessment of feed production potential in the season(s) ahead, taking account of seasonal climate predictions etc

Opportunistic feed opportunities (stubble and Lucerne) on neighboring cropping country

The table and chart below indicate the grazing loads for each grazed paddock between the first and last soil samplings. Grazing loads are expressed, over the period between samplings, as:

(i) The number of days the paddock was grazed (ii) ‘Grazing Days’ or GD (cumulative daily head of stock in the paddock) (iii) ‘DSE Grazing Days’ or DSE GD (GD calibrated to dry sheep equivalent rating) (iv) DSE per paddock hectare

An aspect explored by this project was the quantity of CO2-e emissions attached to the grazing operations that, in the case of the generation of carbon credits, would offset the carbon actually sequestered in soil. Sheep CO2-e emissions (per paddock hectare) were calculated assuming an emissions factor of 141 kg CO2-e/ha (taken from White & van Rees, 2011) for each DSE. This is converted to kg C/ha (dividing by 3.6, the CO2:C molecular weight ratio) in order to compare directly to with the quantum of carbon sequestered in the soil.

This analysis shows that emissions for the paddocks only varied between 0.01 and 0.12 Mg C/ha during the course of the project, this an order of magnitude less than the proposition in the project for a sequestration rate of 2.0 Mg C/ha/yr in the top 30cm of soil. This analysis shows that emissions from a low intensity grazing enterprise (ie. that is in sympathy with carrying capacity and pasture regeneration needs) should not outweigh a conservative sequestration goal. Of course over this project we have not seen a statistically significant soil carbon increase, and that the actual rates of soil carbon sequestration remain to be proven.

33


Table 7.1: Sheep activity and estimated emissions by paddock (for period Nov12-Jul15)

FOSC2.1 FOSC3.2 FOSC4.1 GMCO7 GMGP2 JCRO2

Area 38 48 33 60 42 40

Actual days grazed 58 20 151 183 62 23

Grazing Days (GD) 12,134 15,280 15,350 35,635 3,542 6,360

DSE GD 19,280 27,645 29,954 65,157 5,313 9,720

DSE GD/ha 507 576 908 1,085 127 243

Cumulative DSE/ha 1.39 1.58 2.49 2.98 0.35 0.67

tC02-e emissions/ha 0.20 0.22 0.28 0.42 0.05 0.09

Equiv. tC/ha 0.05 0.06 0.06 0.12 0.01 0.03

Notes: 1 DSE/yr = 141 kg CO2-e/yr

Tri

Figure 7.1: Paddock grazing activity reflected as ‘Grazing Days’ and CO2-e emissions

34


8. Conclusion

In the timeframe of this project, especially in a circumstance of low net soil carbon accumulation rates in in a low soil carbon environment, it was not possible to demonstrate a statistically significant change in soil carbon levels under the tested land use scenarios. This result was obtained not withstanding that there were several technical challenges overcome during the course of the project.

This project has demonstrated that a long term, multi-decadal approach is likely required to build statistically measurable soil carbon stocks in the dry (but climatically variable) inlands of Australia. A decade or more may be necessary to resolve a statistically significant outcome where there is low sequestration rates associated with environments of limited vegetation growth rates.

Despite this there is a need to profitably manage reclaimed dryland areas to support farm incomes. At a minimum these areas need to be managed to control vermin and weeds. More imaginatively they can be managed to build biological, physical and therefore financial resilience across the greater farm. Building carbon in dryland soils should contribute to this farm resilience, and also lead to opportunities for greater production off these areas.

To build carbon in semi-arid soils will require a strong enduring discipline to appropriate paddock management and monitoring to validate change. Though there is some direct financial incentive for this by developing products for the carbon market, there is currently a challenge in generating sufficient revenue to cover the significant transaction costs of carbon measurement (and other) in limiting physical environments.

35


References

Baldock J., 2015. Soil organic carbon: approaches to measuring stocks. Presentation at the National Carbon Farming Expo, Albury, July 2015.\

Carson J., 2014. How much carbon can soil store? Fact Sheet for soilquality.org.au. Healthy Soils for Sustainable Farms programme, of the Australian Government’s Natural Heritage Trust.

DPI, 1997. Dry Sheep Equivalents for comparing different classes of livestock. Agriculture Notes. Victorian Department of Primary Industries

ENRC, 2010. Inquiry into Soil Carbon Sequestration in Victoria. Parliament of Victoria. Paper No. 362, Session 2006-10.

White B. & van Rees H., 2011. Greenhouse gas emissions from farms in the Victorian Wimmera‐Mallee. Report for the Birchip Cropping Group.

http://www.carbonfarmersofaustralia.com.au/CarbonConference2015/key-speakers.html

http://www.soilquality.org.au/factsheets/how-much-carbon-can-soil-store

http://www.agronomy.com.au/download/dseratings.pdf

http://www.parliament.vic.gov.au/images/stories/committees/enrc/20100902.enrc.scsv.FINREP.pdf

rt kilter finaltechoutcomes aotgr1-167 draft (44876) · project outline acceptance and release...

Documents