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Biological Supplement Trials

‘Formosa’ – Pasture

&

‘Oakdene’ - Cropping

Final Report

Produced by

Stephen Ives

November 2013

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Project Details Project Title: Biological Supplement Trials on Cropping and Pasture

Project Leader: Dr Stephen Ives

PO Box 287

Longford Tas 7301

Telephone: +61 (0) 4 0058 6163

Email: [email protected]

Collaborator: Tasmanian Institute of Agriculture

PO Box 46

Kings Meadows TAS 7249

Telephone: +61 (0) 3 6336 5372

Facsimile: +61 (0) 3 6336 5395

Mobile: +61 (0) 4 0791 2761

Partner - Cropping: Mr Bill Chilvers

Eskfield Farms Pty Ltd

PO Box 125

Evandale TAS 7212

Partner - Pasture: Mr Rob Henry

Woodrising Farms

767 Delmont Road

Cressy TAS 7302

NRM North: Adrian James Regional Landcare Facilitator/CFI Extension Officer Level 2 McKenzie Building 63-65 Cameron Street

Launceston TAS 7250

Funding Sources:

We acknowledge the funding support provided to undertake this research and extension

project by NRM North through the Australian Government.

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Contents 1 Introduction .....................................................................................................1

2 Methods ..........................................................................................................2 2.1 Formosa - Site .................................................................................................................................... 2 2.2 Formosa - Treatments ....................................................................................................................... 2 2.3 Formosa – Soil Sampling and Testing ................................................................................................ 4 2.4 Formosa – Pasture Yield and Biomass ............................................................................................... 5 2.5 Oakdene - Site ................................................................................................................................... 6 2.6 Oakdene - Treatments ....................................................................................................................... 6

2.6.1 Small Scale Biochar Trial........................................................................................................ 6 2.6.2 Large Scale Trial .................................................................................................................... 9

2.7 Oakdene – Soil Sampling and Testing .............................................................................................. 11 2.8 Oakdene – Crop Yield and Biomass ................................................................................................. 11

2.8.1 Small Scale Biochar Trial...................................................................................................... 11 2.8.2 Large Scale Trial .................................................................................................................. 11

3 Results ........................................................................................................... 13 3.1 Treatment Analysis .......................................................................................................................... 13 3.2 Formosa Pasture Trial ...................................................................................................................... 15

3.2.1 Soil pH and EC ...................................................................................................................... 15 3.2.2 Soil Carbon and Nitrogen .................................................................................................... 16 3.2.3 Pasture Biomass .................................................................................................................. 18

3.3 Oakdene Small Scale Biochar Cropping Trial ................................................................................... 18 3.3.1 Soil pH and EC ...................................................................................................................... 18 3.3.2 Soil Carbon and Nitrogen .................................................................................................... 20 3.3.3 Crop Growth ........................................................................................................................ 21

3.4 Oakdene Large Scale Cropping Trial ................................................................................................ 24 3.4.1 Soil pH and EC ...................................................................................................................... 24 3.4.2 Soil Carbon and Nitrogen .................................................................................................... 25 3.4.3 Crop Growth ........................................................................................................................ 28

4 Discussion ...................................................................................................... 29 4.1 Soil pH & EC ..................................................................................................................................... 29

4.1.1 Soil pH .................................................................................................................................. 29 4.1.2 Soil EC .................................................................................................................................. 30

4.2 Soil Carbon and Nitrogen................................................................................................................. 30 4.2.1 Soil total carbon .................................................................................................................. 30 4.2.2 Soil total nitrogen ................................................................................................................ 30

4.3 Plant growth .................................................................................................................................... 31

5 Conclusion ..................................................................................................... 32

6 References ..................................................................................................... 33

7 Budget and In Kind Contributions ................................................................... 34

Executive Summary Pasture and cropping trials were established at ‘Formosa’ and “Oakdene’ respectively to

determine the effects of biological (organic) and inorganic soil amendments on soil pH,

total nitrogen and total carbon in the top 10 cm of soil over a 2 – 3 year period. Applied

treatments included two different composts (both sites), inorganic fertiliser (both sites),

biologically enhanced manure digest liquid (Formosa), liquid poppy waste (Formosa),

solid poppy waste (Oakdene), cattle feedlot waste (Oakdene), biological supplement (a

bacterial formulation in a molasses solution - Oakdene), and biochar (small scale trial –

Oakdene).

The results showed a decrease in soil carbon and nitrogen under long term pasture in the

first eighteen months after application of compost concomitant with an increase in

pasture productivity. The increase in productivity may have been due to increased

nutrient release from an increase in activity of the soil fauna in response to the compost

applications. Although both soil carbon and nitrogen showed a subsequent increase up

until the end of the project, the results demonstrate that repeat application may be

necessary to maintain soil carbon over the longer term.

Annual cropping in the large scale trail showed mixed results with no clear distinction

between treatments within each year. This was despite the use of no-till techniques and

incorporation of amendments through ground disturbance with direct drill planting.

However, across the three years the compost from Woodrising Farms (WCP) showed

significantly higher soil carbon and nitrogen. The decline in the third year indicates that

similar to long term pasture, repeat applications may be necessary to maintain soil carbon

levels. This trial shows that applications may be required at least once every two years.

The addition of a carbon source to the soil in the form of biochar showed an increase in

both pH and nitrogen, nine months after application. However, this was short lived with

subsequent decreases over the following 2 years.

These series of trials has shown that a single application of organic amendments on both

cropping and long term pasture in an effort to increase soil carbon may not be effective in

the long term. However, the results have given an indication of the frequency that may be

required. Although longer term trials may provide the answers required to assist in

determining application frequency, fully characterising the amendments and their

behaviour in different soil types and environments for modelling may be a more cost

effective method.

Final report: Biological Supplement Trials

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1 Introduction Organic fertilisers or organic soil amendments such as animal manures, crop residues,

composts and sewage sludge have been used in agriculture since cultivation of crops

began. They supply plant nutrients and improve soil properties. In recent times, modern

society has regarded agricultural residues and bi-products of urbanisation and

industrialisation as waste products for disposal. Therefore, amendment availability and

logistical limitations have often determined application timing and rate for agriculture use

rather than the demand for nutrients and organic matter. However, the use of organic

soil amendments has gained momentum in productive agriculture with the recent

emphasis on soil health and carbon sequestration together with increasing cost of

inorganic fertilisers.

Inorganic fertilisers are manufactured to specific formulations, enabling the calculation of

reasonably accurate and balanced application rates to satisfy plant requirements.

Conversely, most waste products used for soil amendments have not been manufactured

for this purpose and contain many nutrients in an ‘organic’ form with unknown or

misunderstood degradation or release rates.

However, this misunderstanding provides an opportunity to investigate the use of specific

waste products in productive agriculture with a view to tailor make products to satisfy the

economic and environmental requirements of the end user. A number of products are

available in Tasmania produced in commercial quantities including composts, cattle

feedlot waste, anaerobically digested and lime amended biosolids and biologically

enhanced liquid from manure digestion. Biochar is also being extensively trialled

throughout Australia, although commercial quantities are not yet available in Tasmania at

a price to be competitive with other amendments.

The main objective of this project was to determine whether or not a selected number of

these products have the potential to increase soil carbon stocks and improve soil pH over

the short to long term in both cropping and long term pasture.

Fully replicated trials were established at two locations in the Northern Midlands of

Tasmania:

• Large scale (>1 ha plots) trial on long term pasture at ‘Formosa’, Cressy in December 2010

• Large scale (>1 ha plots) trial on annual cropping at ‘Oakdene’, Midlands Highway, Perth in May 2011.

• Small scale (15 m2 plots) trial on annual cropping at ‘Oakdene’, Midland Highway, Perth in May 2011.


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2 Methods

2.1 Formosa - Site

The site was located at ‘Formosa’, 1903 Cressy Road, Cressy, Tasmania. Property ID

6751390, Title Reference 148118/1, Grid Reference 55G 509100m E, 5380600m S,

Elevation 154m (South west corner of Paddock No. 5). Refer to

Figure 1.

Figure 1 Biological Supplement Pasture Trial Site, ‘Formosa’, Cressy, Tasmania

2.2 Formosa - Treatments

The treatments selected for this site were Biological enhanced manure digest liquid, two

different compost products, inorganic fertiliser and liquid poppy waste. Refer to Table 1.

This paddock was a long term pasture with a mixed sward of Brome, Ryegrass, Sub and

White Clover and weed grasses winter grass and barley grass. All treatments were applied

in year 1 in the week 22nd to 24th December 2010 (Figure 2 and Figure 3).

The treatments were set out in a randomised complete block with 4 replicates.


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Table 1 Large scale plot trial for organic and inorganic treatments

Description Code Rate / ha Plot Size Replicates

Biologically enhanced

manure digest liquid MDL 200 L 29 m x 320 m 4

Renew Compost RCP 15 m3 29 m x 320 m 4

WRF Compost WCP 15 m3 29 m x 320 m 4

Inorganic fertiliser

(DAP) INF 250 kg 29 m x 320 m 4

Unamended control CTL N/A 29 m x 320 m 4

Liquid Poppy Waste LPW 200 L 29 m x 320 m 4

Figure 2 Spreading ‘Woodrising Compost’ at Formosa in December 2010


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Figure 3 Applying Manure Digest Liquid at Formosa in December 2010

Spreading of the dry flowable treatments was a straight forward process using a loader

and fertiliser spreading truck. However, one of the liquid amendments presented some

challenges. The biologically enhanced manure digest liquid contained particles that

remained in suspension and kept blocking the filters on the spray jets. Ultimately the

filters were removed and the application was successful. Although this product is no

longer available due to changes in waste water treatment and distribution processes in

Tasmania, management of problems may be helpful for similar products in the future.

2.3 Formosa – Soil Sampling and Testing

Twenty soil cores to a depth of 10 cm were taken from each plot before application of any

treatments, mixed in a composite sample and sub-sampled for analysis. Further sampling

of individual plots was undertaken in March and October 2012, and March and November

2013.

Cores were taken in a straight line transect along each plot. Samples were stored in cooler

boxes out of direct sunlight while out in the field, and then transferred to aluminium trays

for drying at 40 ˚C for at least 48 hours or until dry. Samples were then ground and sieved


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to pass through a 2 mm sieve and sent to Agvita Analysis Laboratory in East Devonport,

Tasmania for analysis of pH (water), electrical conductivity, Total Carbon and Total

Nitrogen.

2.4 Formosa – Pasture Yield and Biomass

There are distinct limitations in monitoring pasture growth in a 30 ha paddock that is

continuously grazed. Due to available feed in other areas of the farm, animals were

locked out of the paddock for 4 weeks in March and October of year 1. A 2.5 m wide strip

was slashed across each plot to a height of 50 mm. After 4 weeks, a mower was used to

cut a strip 2 m long across each plot, clippings collected, dried at 56 ˚C and weighed for

biomass production. The sampling protocol changed in years 2 and 3 because low feed

availability meant that the trial paddock was required for continuous grazing. The new

protocol adopted was the use of 50 cm x 50 cm galvanised steel mesh grazing exclusion

cages placed on a mowed strip for a set period, with the new growth cut, dried and

weighed for biomass production (Figure 4). Although the cages were pinned to the

ground with long metal pegs, grazing cattle were able to dislodge them and prevent

pasture growth being measured in both the October 2012 and the May 2013 sampling

period.

Figure 4 Galvanised grazing exclusion cages used at the ‘Formosa’ trial site


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2.5 Oakdene - Site

The site was located at ‘Oakdene’, Midland Highway, Perth, Tasmania. Property ID

1723518, Title Reference 105209/1, Grid Reference 55G 519900m E, 5389200m S,

Elevation 174m (east corner). Refer to

Figure 5.

Figure 5 Biological Supplement Cropping Trial Site, ‘Oakdene’, Perth, Tasmania

2.6 Oakdene - Treatments

Due to the high cost of purchasing enough biochar for large scale use (~ $2500 /tonne),

two trials were established at the site; a small plot trial comparing the use of biochar with

inorganic fertiliser and combinations thereof, and a large plot trial comparing the

remainder of the treatments

2.6.1 Small Scale Biochar Trial

Treatments for the small scale trial included Biochar at 0, 10 and 20 t/ha (Figure 6),

control, unamended control and inorganic fertiliser (DAP). Basal fertiliser was provided as

shown in Table 2.


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Figure 6 Biochar applied to soil surface before being turned in.

Table 2 Small plot trial for biochar and inorganic fertiliser treatments

Description Rate / ha Basal

Fertiliser

Plot Size Replicates

Biochar 0 120kg/ha

DAP 10 m x 1.5 m 5

Biochar 10 t 120kg/ha

DAP 10 m x 1.5 m 5

Biochar 20 t 120kg/ha

DAP 10 m x 1.5 m 5

Control N/A 120kg/ha

DAP 10 m x 1.5 m 5

Unamended control N/A Nil 10 m x 1.5 m 5

DAP 120 kg 120kg/ha

DAP 10 m x 1.5 m 5

Treatments were incorporated in the top 10cm as shown in Figure 7.

20 t/ha

10 t/ha


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Figure 7 Incorporation of all treatments in the small scale Biochar trial

Wheat variety ‘Revenue’ was planted at 92 kg/ha in year 1 (16th May 2011) with a small

plot planter and in year 2 and year 3 using a commercial planter for wheat and canola

respectively (Figure 8). All treatments were applied in year 1 (10th May 2011) with a basal


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fertiliser of 120 kg/ha DAP, and a further 240 kg/ha of DAP applied with seed at planting

for years 2 and 3.


Figure 8 Direct drilling year 2 wheat ‘Revenue’ at Oakdene

2.6.2 Large Scale Trial

The treatments selected for this site were Biological enhanced manure digest liquid, two

different compost products, cattle feedlot waste, inorganic fertiliser and solid poppy

waste. (Table 3 and Figure 9).

Wheat variety ‘Revenue’ was planted in years 1 and 2 at 92 kg/ha with Canola planted in

year 3. All treatments were applied in year 1 (10th May 2011) with a basal fertiliser of 120

kg/ha DAP, with a further 240 kg/ha of DAP applied with seed at planting for years 2 and

3.



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Table 3 Large scale plot trial for organic and inorganic treatments

Description Code Rate / ha Plot Size Replicates

Biologically enhanced

manure digest liquid MDL 200 L 20 m x 450 m 4

Renew Compost RCP 15 m3 20 m x 450 m 4

WRF Compost WCP 15 m3 20 m x 450 m 4

Inorganic fertiliser

(DAP) INF 125 kg 20 m x 450 m 4

Unamended control CTL N/A 20 m x 450 m 4

Cattle feedlot waste CFW 15 m3 20 m x 450 m 4

Solid Poppy Waste SPW 15 m3 20 m x 450 m 4

Figure 9 Poppy waste (1), Renew Compost (2), Cattle Feedlot Waste (3) and

Woodrising Compost (4) applied at Oakdene

1

3

2

4


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2.7 Oakdene – Soil Sampling and Testing

Twenty soil cores to a depth of 10 cm were taken from each plot of the large scale trial

before application of any treatments, mixed in a composite sample and sub-sampled for

analysis. Further sampling of individual plots of both the large (20 cores per plot) and

small (10 cores per plot) scale plots was undertaken in March 2012, March 2013 and

November 2013.

Cores were taken in a straight line transect along each plot. The beginning of each

transect for the large scale plots was identified with a GPS mark. Samples were stored in

cooler boxes out of direct sunlight while out in the field, and then transferred to

aluminium trays for drying at 40˚C for at least 48 hours or until dry. Samples were then

ground and sieved to pass through a 2 mm sieve and sent to Agvita Analysis Laboratory in

East Devonport, Tasmania for analysis of pH (water), electrical conductivity, Total Carbon

and Total Nitrogen.

2.8 Oakdene – Crop Yield and Biomass

2.8.1 Small Scale Biochar Trial

Plant density and vigour scores out of 10 were taken along with photos on 5th August

2011. Biomass samples were taken at GS30 in year 1 (14th September 2011) using 3 x 500

mm x 500 mm quadrats per plot. The sample from each plot was dried at 56 °C and

weighed. Harvest yields from the small scale biochar trial in year 1 were recorded from 2

x 500 mm x 500 mm quadrats per plot and also using a small plot harvester with yields

taken from whole plots. Harvest yields for year 2 were recorded using a 500 mm x 500

mm quadrat. The year 3 crop was still in a vegetative state at the completion of this

project, so only plant height and growth stage were recorded. Furthermore, results may

have been confounded because of cross contamination between treatments by the

commercial planter planting across the plots (1.5 m wide) in Year 3.

2.8.2 Large Scale Trial

Harvest yields from the large scale trial in year 1 were recorded from the yield monitor in

the commercial harvester from a 9.1 m wide pass up the centre of each plot with an

average length of 300 m. Harvest yields for year 2 were recorded using a 500 mm x 500

mm quadrat. However, no yield has been recorded for the canola crop for year 3 as it is

still in the vegetative state. Biomass has also not been recorded for year 3 as extensive

rain and a perceived micro nutrient deficiency of the canola (by the farmer) throughout

the growing period have resulted in a non-uniform emergence and growth (Figure 10).


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Figure 10 Large scale trial at Oakdene planted with Canola in year 3


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3 Results

3.1 Treatment Analysis

An analytical summary of treatments used at Formosa and Oakdene (including pre-trial

soil) is shown in

Table 4 and Table 5 respectively.

Table 4 Formosa treatment and soil analysis

Analyte FORMOSA

SOIL

RCP WCP LPW (mg/L)

Colwell P (mg/kg) 56.5 1022 2592 13300

Colwell K (mg/kg) 239 2822 9990 95500

Ca (mg/kg) 1938 6367 7490 NR

Mg (mg/kg) 193 3003 3155 9.67

Zn (mg/kg) 2.67 14.2 52.1 3.62

B (mg/kg) 0.11 3.59 11.8 5.38

S (mg/kg) 28.8 984 1083 9780

Cu (mg/kg) 0.27 1.86 1.31 0.27

Fe (mg/kg) 536 135 181 NR

Mn (mg/kg) 70.6 52.6 74.2 NR

Na (mg/kg) 61.1 893 240 NR

EC (dS/m) 0.34 1.67 4.43 NR

pH (H2O) 5.87 7.26 7.65 NR

pH (CaCl2) 5.53 7.01 7.40 NR

Cl (mg/kg) 59.5 200 2390 7130

Total N (%) 0.27 1.33 1.97 7140

Total C (%) 3.43 29.5 16.9 5700

C/N Ratio 12.6 22.1 8.47 NR

Note: NR indicates no result for analyte


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Table 5 Oakdene treatment and soil analysis

Analyte OAKDENE

SOIL

CFW SPW RCP WCP Biochar

Colwell P (mg/kg) 50.2 3052 2706 1022 2592 5100

Colwell K (mg/kg) 111 11686 8469 2822 9990 41500

Ca (mg/kg) 896 7213 46586 6367 7490 5500

Mg (mg/kg) 93.2 2853 8983 3003 3155 3000

Zn (mg/kg) 2.54 366 16.3 14.2 52.1 53.5

B (mg/kg) 0.49 4.32 25.2 3.59 11.8 8.14

S (mg/kg) 15.6 353 837 984 1083 1800

Cu (mg/kg) 0.23 3.52 1.14 1.86 1.31 11.89

Fe (mg/kg) 474 240 77.9 135 181 1418

Mn (mg/kg) 42.9 133 72.1 52.6 74.2 205.1

Na (mg/kg) 22.3 3458 338 893 240 300

EC (dS/m) 0.18 4.06 2.47 1.67 4.43 NR

pH (H2O) 5.28 7.33 8.73 7.26 7.65 NR

pH (CaCl2) 4.84 6.96 8.41 7.01 7.40 NR

Cl (mg/kg) 22.9 7987 488 200 2390 NR

Total N (%) 0.25 1.83 1.57 1.33 1.97 2.39

Total C (%) 3.24 18.1 31.4 29.5 16.9 NR

C/N Ratio 12.7 9.84 20 22.1 8.47 NR

Note: NR indicates no result for analyte. Biochar was produced from wheat stubble,

which may explain the high value for Colwell K.


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3.2 Formosa Pasture Trial

3.2.1 Soil pH and EC

Analysis of the top 10 cm for pH and EC showed no significant differences between

treatments either with all years combined or within each year (Refer to Figure 11 and

Figure 12). Interestingly the pH for the WCP treatment remained constant for the

duration of the trial.

Figure 11 Soil pH (H20) in the top 10 cm at the Formosa site

Note: Error bars indicate standard deviation of the means

The May 2012 sampling occurred in a very dry autumn, with subsequent samplings being in

wetter periods. The decrease in EC (Refer to Figure 12) over time suggests the downward

movement (or lack of) of the dissolved salts in the soil matrix during wet (and dry) periods.


16

Figure 12 Soil EC in the top 10 cm at the Formosa site


3.2.2 Soil Carbon and Nitrogen

The analysis of the top 10 cm of each of the treatments at the Formosa pasture site

showed significant differences between treatments for both soil carbon and nitrogen, but

only in the May 2012 sampling period. Refer to Figure 13 and Figure 14. Treatments MDL,

RCP and WCP were significantly lower in soil carbon and nitrogen than the control

treatment.


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Figure 13 Total carbon in the top 10 cm at the Formosa site

Note: Error bars indicate standard deviation of the means and different letters

indicate significant difference between treatments (P=0.002, LSD=0.46)

Figure 14 Total nitrogen in the top 10 cm at the Formosa site




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3.2.3 Pasture Biomass

The pasture biomass showed no significant differences between treatments for any year

for the trial (Refer to Figure 15). The May 2012 sampling displayed a trend suggesting

MDL, RCP and WCP treatments were responding positively to the soil amendment.

However, there was a high variability within each treatment (indicated by the error bars).

Figure 15 Pasture biomass at the Formosa site


3.3 Oakdene Small Scale Biochar Cropping Trial


There were significant treatment differences between biochar treatments and the

remaining treatments in the small scale cropping trial after year 1, with both pH and EC

higher for them 10 and 20 t/ha biochar treatments. However, in years 2 and 3, there

were no significant differences between the treatments. Refer to Figure 16 and Figure 17.


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Figure 16 Soil pH for years 1, 2 & 3 at the Oakdene Biochar cropping site


indicate significant difference between treatments (P<0.001, LSD=0.22)

Figure 17 Soil EC for years 1, 2 & 3 at the Oakdene Biochar cropping site



a a a b b

a a a b c


20


Analysis of the top 10 cm of soil after year 1, showed a significant increase of soil carbon

for the 20 t/ha biochar and the 240 kg/ha DAP treatments compared to the fertilised

control (0/120). Although no significant differences were found in years 2 and 3, there

was a downward trend in soil carbon for the 20 t/ha biochar treatment. Refer to Figure

18.

Figure 18 Soil total carbon for years 1, 2 & 3 at the Oakdene Biochar cropping site



Analysis of the top 10 cm of soil after year 1, showed a significant increase of soil total

nitrogen for the 10 and 20 t/ha biochar, and the 240 kg/ha DAP treatments compared to

the fertilised control (0/120). Although no significant differences were found in years 2

and 3, there appeared to be a downward trend in soil total nitrogen for all treatments

excepted for the fertiliser control (0/120). Refer to Figure 19.

ab a b ab c


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Figure 19 Soil total nitrogen for years 1, 2 & 3 at the Oakdene Biochar cropping site



3.3.3 Crop Growth

Crop growth was assessed in the first year in terms of vigour and biomass at GS 30. The

biochar and fertilised treatments were all significantly more vigorous and had a higher

biomass than the unfertilised control (0/0). Refer to Figure 20 and Figure 21. However,

the biochar treatments were not significantly higher in biomass than the 240 kg/ha DAP

treatment (0/240).

At the end of year 1, the 10 and 20 t/ha biochar treatments and the 240 kg/ha DAP

treatments yielded significantly higher than the fertilised (0/120) and unfertilised (0/0)

control treatments (Refer to Figure 22). Although treatment differences appeared similar

at the end of year 2, the differences were not significant. In year 3, height of the canola

crop at GS 71 showed a difference between the 20t/ha Biochar treatment and all other

treatments, although not significant (P=0.082). Refer to Figure 23.

ab a b b c


22

Figure 20 Year 1 wheat vigour rating for Oakdene Biochar trial at GS21-30



Figure 21 Year 1 biomass for Oakdene Biochar trial at GS21-30



a b bc cd d

a b c c c


23

Figure 22 Year 1 & 2 wheat yield for Oakdene Biochar trial



Figure 23 Year 3 height of canola for Oakdene Biochar trial



24

3.4 Oakdene Large Scale Cropping Trial


In year 2, pH of the control treatment was significantly higher than CFW and MDL.

However, there were no significant differences between treatments in years 1 and 3.

Furthermore, there were no significant differences between treatments for EC in any year

of sampling. Refer to Figure 24 and Figure 25.

Figure 24 Soil pH - large scale cropping trial, Oakdene for years 1, 2 and 3

Note: Error bars indicate standard deviation of the means and different letters indicate significant difference between treatments (P=0.03, LSD=0.19)


25

Figure 25 Soil EC at the large scale cropping trial, Oakdene for years 1, 2 and 3



There were no significant differences between treatments at the end of each cropping

year for soil total carbon and nitrogen. However, analysing the combined data for all

years showed that WCP treatment was significantly higher than any other treatment

(except INF with total carbon) for both anolytes. Refer to Figure 26 and Figure 27 for soil

total carbon, and Figure 28 and Figure 29 for soil total nitrogen.


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Figure 26 Soil total carbon - large scale trial, Oakdene for years 1, 2 & 3


Figure 27 Soil total carbon – large scale trial, Oakdene for 3 years combined

Note: Error bars indicate standard deviation of the means and different letters indicate significant difference between treatments (P=0.028, LSD=0.45)


27

Figure 28 Soil total nitrogen - large scale trial, Oakdene for years 1, 2 and 3


Figure 29 Soil total nitrogen – large scale trial, Oakdene for 3 years combined




28

3.4.3 Crop Growth

Crop yield for year 1 showed no significant differences between treatments. However, in

year 2 SPW, yielded significantly higher than all other treatments (except Control and

WCP). The caveat on the year 2 result is that yield assessments were taken from 500 x

500 mm quadrats on each plot instead of the yield monitor used in year 1. Due to the

large plots (1 ha), the latter method would be more consistent and account for variability

within each plot. Refer to Figure 30.

Figure 30 Crop yield at the large scale cropping trial, Oakdene for years 1, 2 and 3


indicate significant difference between treatments


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4 Discussion Many bio-resources used in agriculture for soil amendments have not been manufactured

for this purpose and contain many nutrients in an ‘organic’ form with unknown or

variable degradation or release rates. Bio-resources such as animal manures and other

organic materials are continually being investigated for use in agriculture (Dong et al.,

2005; Flavel and Murphy, 2006) and are often applied to soil in lieu of inorganic fertiliser

to supply essential plant nutrients (Golabi et al., 2007; Kidd et al., 2007). However, the

inherent difficulty with using alternative materials is the variation and availability of

nutrients depending on management, product composition and consistency. The main

objective of applying the range of bio-resources used in the pasture and cropping trials

reported was to determine any changes in soil carbon, nitrogen and pH over the short to

medium term.

A decrease soil organic carbon (SOC) can negatively affect soil physical functions including

structural stability, water holding capacity and thermal properties (Baldock and

Skjemstad, 1999). Such decreases can be exacerbated through conventional tillage and

irrigation (Gwenzi et al., 2009), which is why trials were conducted on pasture as well as

in a cropping situation.

4.1 Soil pH & EC

4.1.1 Soil pH

The soil pH of the pasture and cropping sites three years after applying treatments were

not significantly different to the pre-trial soil test. After year 1 the biochar trial did show a

significant increase in pH with the 20 t/ha Biochar + 120 kg/ha DAP. After year 2, the large

scale trial showed that the pH for Cattle Feedlot Waste (CFW) and manure digest liquid

(MDL) was significantly lower than all other treatments. Given that the pH of most of the

treatments pre-application was below 7.7 (except SPW at 8.73) and soil pH can change

depending on time of year, it was unlikely that there would be any significant increase in

pH as a result of the amendment applications. Although pH under pasture has been

known to decrease over time, the use of chemical fertilisers has also shown a decrease in

pH that is then addressed with a lime application. The decrease in pH for all treatments at

Formosa under long term pasture may have been due to the wet winter spring

experience in 2013.


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4.1.2 Soil EC

Although there were some significant differences between treatments in the small scale

biochar trial for EC, the absolute values are still within an acceptable range for crop

growth. The main point of measuring EC is to ensure that dissolved salts from the

amendments do not accumulate in the soil over time and create plant growth issues

associated with salinity.

4.2 Soil Carbon and Nitrogen

4.2.1 Soil total carbon

Total carbon measured at the Formosa site showed a decrease from pre-trial levels for all

organic treatments in year 2. This appeared to be inversely related to the crop growth for

the same period, which showed a trend increase in pasture yield for the same treatments

(not significant). However, by the end of the trial all treatments had shown an increase in

soil carbon from pre-trial levels. Previous research has shown that soil carbon can be

maintained under long term pasture although fluctuations can occur as a result of wet

and dry seasons.

In the cropping trial, soil carbon for the 20 t/ha biochar treatment was significantly higher

than the other treatments after the first year and higher than pre-trial levels. Although

biochar is added to soils (as a stable source of carbon) to increase soil carbon, this trial

was looking at the longevity of this type of treatment to maintain soil carbon levels. All

other treatments decreased from pre-trial levels after the first year as a result of the

cropping (all treatments were cultivated in). Only the 20 t/ha biochar treatment remained

above pre-trial soil carbon levels at the end of the three year trial. This suggests that in a

cropping regime, even adding biochar does not provide a long term solution for

maintaining soil carbon.

The large scale cropping trial, which was direct drilled, showed that the WCP treatment

significantly increased soil carbon more than the other treatments and more than pre-

trial levels. However, the results also show that a single application may only last for 2

years before re-application is needed.

4.2.2 Soil total nitrogen

Total nitrogen at the Formosa long term pasture site showed a decrease in the first year,

similar to the carbon trend. However, levels at the end of the trial were not lower than

pre-trail soil nitrogen.

In the biochar trial, the significant increase in Total N for the 20 t/ha biochar treatment

was not sustained over the length of the trial. However, similar to the soil carbon, the

high biochar treatment did not result in lower total N at the end of the trial than pre-trial

levels.


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Total nitrogen for the large scale cropping trial at Oakdene followed a similar trend to the

soil carbon, with WCP treatment being significantly higher across the three years.

4.3 Plant growth

Plant response to soil amendments has been regarded by Warman (1998), as being

influenced more by seasonal variation in soil moisture and temperature than by the

added amendment. Maynard and Hill (1994) also suggested that compost amendments

might not provide immediate effects to plants in one application, and that sustained

applications might result in cumulative effects. The results of the pasture and cropping

trials showed that increased yields can be obtained from applying 10 and 20 t/ha biochar

in the first year. However, the results suggest that single applications of soil amendments

over the longer term will not maintain consistent results.


32

5 Conclusion The pasture and cropping trials established at ‘Formosa’ and “Oakdene’ respectively to

determine the effects of biological (organic) and inorganic soil amendments on soil pH,

total nitrogen and total carbon in the top 10 cm of soil over a 2 – 3 year period, showed

varied responses.

The results showed a decrease in soil carbon and nitrogen under long term pasture in the

first eighteen months after application of compost concomitant with an increase in

pasture productivity. The increase in productivity may have been due to increased

nutrient release from an increase in activity of the soil fauna in response to the compost

applications. Both soil carbon and nitrogen showed a subsequent increase up until the

end of the project. The results demonstrate that repeat application may be necessary to

maintain soil carbon over the longer term; however, longer term measurements would be

required to determine the appropriate application frequency.

Annual cropping in the large scale trail showed mixed results with no clear distinction

between treatments within each year. This was despite the use of no-till techniques and

incorporation of amendments through ground disturbance with direct drill planting.

However, across the three years the compost from Woodrising Farms (WCP) showed

significantly higher soil carbon and nitrogen. The decline in the third year indicates that

similar to long term pasture, repeat applications may be necessary to maintain soil carbon

levels. This trial shows that applications may be required at least once every two years.

The addition of a carbon source to the soil in the form of biochar showed an increase in

both pH and nitrogen, nine months after application. However, this was short lived with

subsequent decreases over the following 2 years.

These series of trials has shown that a single application of organic amendments on both

cropping and long term pasture in an effort to increase soil carbon may not be effective in

the long term. However, the results have given an indication of the frequency that may be

required. Although longer term trials may provide the answers required to assist in

determining application frequency, fully characterising the amendments and their

behaviour in different soil types and environments for modelling may be a more cost

effective method.


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6 References Baldock, J A and Skjemstad, J O (1999). Soil Organic Carbon/Soil Organic Matter. Soil

Analysis: an interpretation manual. K. I. Peverill, L. A. Sparrow and D. J. Reuter.

Collingwood, CSIRO Publishing: 159-170.

Dong, Y, Ouyang, Z and Liu, S (2005). "Nitrogen transformation in maize soil after

application of different organic manures." Journal of Environmental Sciences 17(2): 340-

343.

Flavel, T C and Murphy, D V (2006). "Carbon and Nitrogen Mineralization Rates after

Application of Organic Amendments to Soil." Journal of Environmental Quality 35(1): 183-

193.

Golabi, M H, Denney, M J and Lyekar, C (2007). "Value of Composted Organic Wastes As

an Alternative to Synthetic Fertilizers For Soil Quality Improvement and Increased Yield."

Compost Science & Utilization 15(4): 267-271.

Gwenzi, W, Gotosa, J, Chakanetsa, S and Mutema, Z (2009). "Effects of tillage systems on

soil organic carbon dynamics, structural stability and crop yields in irrigated wheat

(Triticum aestivum L.)–cotton (Gossypium hirsutum L.) rotation in semi-arid Zimbabwe."

Nutrient Cycling in Agroecosystems 83(3): 211-221.

Kidd, P S, Dominguez-Rodriguez, M J, Diez, J and Monterroso, C (2007). "Bioavailability

and plant accumulation of heavy metals and phosphorus in agricultural soils amended by

long-term application of sewage sludge." Chemosphere 66(8): 1458-1467.

Maynard, A A and Hill, D E (1994). "Impact of compost on vegetable yields." BioCycle 35:

66-67.

Warman, P R and Havard, K A (1998). "Yield, vitamin and mineral contents of organically

and conventionally grown potatoes and sweet corn." Agriculture, Ecosystems and

Environment 68: 207-216.


34

7 Budget and In Kind Contributions

Date Details Amount GST Total

Fund Allocation

Nov-10 NRM North to CPR 12390 1239 13629

NRM North to Woodrising Farms 13920 1392 15312

May-11 NRM North to CPR 15000 1500 16500

NRM North to Eastfield 6440 644 7084

Total Funding 47750 4775 52525

Formosa - Broad Acre Pasture Trial - Expenditure

Nov-10 Project Materials 184 18 203

Dec-10 Project Materials 519 52 571

Nov-10 Ute Hire 41 4 45

Dec-10 Ute Hire 227 23 250

Dec-10 Site Set-up 1200 120 1320

Dec-10 Soil Sampling 3600 360 3960

Dec-10 Treatment Application 2400 240 2640

Jun-11 Sampling - Contractor 3052 305 3357

May-12 Soil and Plant sampling 3600 360 3960

May-12 Soil Analysis 980 98 1078

Oct-12 Soil and Plant sampling 3600 360 3960

Oct-12 Soil Analysis 980 98 1078

May-13 Soil and Plant sampling 3600 360 3960

May-13 Soil Analysis 980 98 1078

Nov-13 Soil and Plant sampling 3600 360 3960

Nov-13 Soil Analysis 1205 121 1326

Nov-13 Reporting 6000 600 6600

Sub-Total Expenditure 35769 3577 39346


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Formosa Broad Acre Pasture Trial - In Kind Contributions

Insurance & Infrastructure 5309 531 5840

Dec-10 Inorganic Fertiliser 750 75 825

Dec-10 Woodrising Compost 900 90 990

Dec-10 Renew Compost 1350 135 1485

Dec-10 Poppy Waste 900 90 990

Dec-10 Microbial Wastewater 200 20 220

Dec-10 Treatment Application 2400 240 2640

May-11 Slashing sampling Area 255 26 281

Oct-11 Slashing sampling Area 255 26 281

May-12 Transport 450 45 495

Oct-12 Transport 450 45 495

May-13 Transport 450 45 495

Nov-13 Transport 450 45 495

Sub-Total In Kind Contributions 14119 1412 15531

Oakdene - Broad Acre Cropping Trial - Expenditure

Apr-11 Area Pegged Out 360

Nov-11 Renew Compost 900 90 990

Feb-12 Soil Sampling 3600 360 3960

May-12 Soil Analysis - Agvita 2030 203 2233


Mar-13 Soil and Plant Sampling 3600 360 3960


Nov-13 Soil and Plant Sampling 3600 360 3960

Nov-13 Soil Analysis - Agvita 2030 203 2233

Nov-13 Reporting 6000 600 6600



36


Oakdene Broad Acre Cropping Trial - In Kind Contributions

Insurance & Infrastructure 5309 531 5840

May-11 Woodrising Compost 900 90 990

Nov-11 Renew Compost - Transport 450 45 495

May-11 Poppy Waste 900 90 990

May-11 Bio Waste 200 20 220

May-11 Cattle Feedlot Waste 900 90 990

May-11 Inorganic Fertiliser 750 75 825

May-11 Treatment Application - Farmer 3600 360 3960

May-11 Planting - Farmer 600 60 660

Feb-12 Harvest - Farmer 900 90 990

Feb-12 Soil Sampling 3600 360 3960

Feb-12 Transport 450 45 495

May-12 Planting - Year 2 600 60 660

Mar-13 Transport 450 45 495

May-12 Planting - Year 3 600 60 660

Nov-13 Transport 450 45 495


Oakdene Small Plot Biochar Trial - Expenditure

Feb-11 Project Materials 397 17 415

Apr-11 Area pegged out 180 18 198

Feb-11 Pacific Parolysis - Biochar 1175 118 1293

Aug-11 Pacific Parolysis - Biochar 1175 118 1293

May-11 Treatments applied 2160 216 2376

May-11 Site Sown 360 36 396

Jun-11 Seed establishment checked 360 36 396

Jun-11 Lines Sprayed 360 36 396

Aug-11 Plant density and vigour scores 1440 144 1584

Sep-11 Checked growth stage 720 72 792

Sep-11 DM cuts done on all plots 1440 144 1584

Feb-12 Harvest Quadrats - UTAS 1751 175 1926

Apr-12 Machine Harvest - UTAS 1751 175 1926



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Details

Amount GST Total

Total Expenditure All Trials 73667 7308 80615

Less Funding Total 47750 4775 52525

Balance (unfunded) 25917 2533 28090


Total In Kind Contributions 60695 6011 66347

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