Soil Biology and Soil pH Interaction project

Year of study:

2011 – 2013

Lead organisation & collaborators:

Macalister Demonstration Farm

Contact:

Sandie Brown

Project details

Objectives

This project aims to investigate management of soil biology in order to reduce fertiliser inputs while maintaining profitable pasture production. The project will:

  • Compare pasture productivity and profitability between paddocks managed using a conventional fertiliser regime and the addition of lime to lift pH from 5.5 to 6.4.

Hypotheses

A rise in pH to 6.4 will result in lower nitrogen fertilizer inputs and equivalent pasture production by enhancing soil biological driven nutrient cycling.

Basis of trial

Increasing soil pH at the same time as adding carbon-based soil amendments (e.g. sugars, fish and seaweed emulsions, humus, compost and worm castings) have been associated with positive pasture, animal health and profitability responses in some cases. However, it is not clear whether it is the change in pH alone, the application of carbon-based additives, or both in combination that are responsible for the observed response.

Interpretation

Summary of key messages/findings of trial

Interim report: May 2012 Six grazing rotations have been harvested and dry matter production measured on a cut and weigh basis. There was an obvious impact on dry matter production between N application rates from the first four cuts which levelled out with subsequent harvests. There is little evidence of any difference between different soil pH levels which is expected as soil pH will take a year or more to recalibrate following the application of lime.

Location and site details

Trial site details

3 years (from 2011)

Rainfall Maffra – (BoM): 566.1mm (2010)

Soil type – This soil type is one of two predominant soil types in the Macalister Irrigation District and is described as Tinamba soil (Ti – Red and Brown Chromosols or Sodosols) in ‘Major Agricultural Soils of the Maffra Region’, Sargeant, I. and Imhof, M. (2000) ISBN 0 7311 4606 9

Landscape position – The project will be established on one site at the Macalister Demonstration Farm that is a free draining soil under fixed spray irrigation that was re-sown in 2010.
Aspect Flat to sloping
pH water – 5.3
Organic carbon 0-10cm – 3.4%
Cation Exchange – 9.57

Management history

Pre-trial management

Strict rotational grazing system under spray irrigation. N applied after each grazing.

Trial management

Grazing and irrigation management has not changed. N is applied by the project officer as described under “Treatments”. The trial plots will be established and managed within the normal farm operations.

Best available science assessment

Objectives Hypothesis Design Soil Analysis Production/ Financial Method Reporting Data Analysis Results reporting Publication
3 3 3 3 2 3 TBA TBA TBA

Experimental design

Treatments

The design is soil pH (3 – 5.5, 6.0, 6.4) x replicates (3) x urea application rates within replicates (3 – 0, 400, 600 kg N/ha/yr). Treatments and the full monitoring program will be in place for three years.

pH 5.3

(No lime)

pH 5.9

(Lime 40kg/plot

pH 6.5

(Lime 80kg/plot

No N

Plot 1

Plot 2

Plot 3

Mid –N (23kgN/ha)

Plot 4

Plot 5

Plot 6

High-N (46kgN/ha)

Plot 7

Plot 8

Plot 9

Trial design/layout

Vardys Rd side 80 kg LIME Plot 1Treatment 3 Plot 2Treatment 6400 g Plot 3Treatment 9800 g Plot 4Treatment 6400 g Plot 5Treatment 9800 g Plot 6Treatment 3 Plot 7Treatment 9800 g Plot 8Treatment 6400 g Plot 9Treatment 3
40 kg LIME Plot 10Treatment 8800 g Plot 11Treatment 2 Plot 12Treatment 5400 g Plot 13Treatment 8800 g Plot 14Treatment 2 Plot 15Treatment 8800 g Plot 16Treatment 5400 g Plot 17Treatment 2 Plot 18Treatment 5400 g
NO LIME Plot 19Treatment 1 Plot 20Treatment 4400 g Plot 21Treatment 7800 g Plot 22Treatment 4400 g Plot 23Treatment 1 Plot 24Treatment 4400 g Plot 25Treatment 7800 g Plot 26Treatment 1 Plot 27Treatment 7800 g

Soil sampling method

Soil chemistry. 10cm depth, 10 in each plot x 3 replicates =, 9 x 30 bulked samples. Soil samples for standard soil tests will be taken in spring (September 30th) in each of the three years of the project. The standard suite of soil chemistry will be measured and will include pH, Total C, Total N, Mineral N (NO3-, NO2-), CEC, and Olsen and Total P.
Sample analysis to be undertaken as ‘blind samples’ to enhance credibility.

Statistical analyses. Results for each management approach will be analysed with multivariate statistical packages that incorporate and identify relationships between multiple data sets.

Microbial community assessment. Half of the final soil chemical sample in September 2013 will be sent to Microbe Wise Lab in Adelaide. 9 x 30 bulked samples to 10cm will be subjected to the suite of tests developed under the National Soil Quality Monitoring Program (Theme 1 GRDC SBI-II) and will include microbe biomass and T-RFLP analyses (Bacteria, Fungi and Archaea).

Production measurements

Plant and/or animal production measurements

Pasture assessment. A series of cut and weigh samples of pasture will also be taken before each grazing to complement a suite of feed tests and plant tissue analyses taken at the same time (10 samples per year).

Treatment results

Variation with time and management influence

Nutrient Advantage Laboratory – Nutrient Report 17

TREATMENT 1 TREATMENT 2 TREATMENT 3 TREATMENT 4 TREATMENT 5 TREATMENT 6 TREATMENT 7 TREATMENT 8 TREATMENT 9
No N, pH 5.3 No N, pH 5.9 No N, pH 6.5 Mid N, pH 5.3 Mid N, pH 5.9 Mid N, pH 6.5 High N, pH 5.3 High N, pH 5.9 High N, pH 6.5

pH (1:5 Water)

5.2 5.8 6.3 5.2 5.8 6.4 5.1 5.9 6.0

pH (1:5 CaCl2)

4.6 5.3 5.9 4.5 5.3 6.0 4.4 5.4 5.6

Elect. Conductivity dS/m)

0.1 0.2 0.2 0.1 0.2 0.2 0.1 0.2 0.2

Elec. Cond. (Sat. Ext.) (dS/m)

0.9 1.3 1.4 0.9 1.2 1.8 1.0 1.1 1.5

Chloride (mg/kg)

40.3 27.3 36.7 26.7 29.0 33.3 29.7 25.0 34.7

Nitrate Nitrogen (NO3) (mg/kg)

19.6 14.0 14.9 18.7 22.3 30.3 22.7 16.0 27.7

Ammonium Nitrogen (KCl) (mg/kg)

13.3 13.7 17.3 13.3 16.7 19.0 16.3 12.7 17.7

Phosphorus (Colwell) (mg/kg)

121.0 140.0 116.3 130.7 117.0 114.7 121.7 88.0 120.0

Phosphorus Buffer Index (PBI-Col)

130.0 163.3 216.7 133.3 163.3 183.3 133.3 166.7 216.7

Available Potassium mg/kg

223.3 203.3 223.3 176.7 233.3 226.7 156.7 223.3 223.3

Calcium (Amm-acet.) (Meq/100g)

5.7 9.5 12.0 5.8 9.2 13.0 5.5 10.0 11.2

Potassium (Amm-acet.) Meq/100g

0.6 0.5 0.6 0.5 0.6 0.6 0.4 0.6 0.6

Magnesium (Amm-acet.) (Meq/100g)

3.0 3.0 4.2 2.9 3.1 4.0 2.4 3.9 3.8

Sodium (Amm-acet.) (Meq/100g)

0.2 0.2 0.3 0.1 0.2 0.3 0.2 0.2 0.1

Calcium/Magnesium Ratio

2.1 3.3 2.9 2.0 3.1 3.4 2.3 2.6 3.0

Sodium (Amm-acet.) %

1.3 1.6 1.2 1.5 1.0 0.9

Aluminium (KCl) (Meq/100g)

0.3 0.1 0.4 0.1 0.4 0.2

Cation Exch Cap Meq/100g

9.7 13.3 17.1 9.7 13.1 17.9 8.9 14.7 15.7

Sodium % of Cations (ESP) %

1.9 1.2 1.5 1.4 1.7 1.1

Aluminium Saturation%

3.2 1.1 3.6 0.9 4.6 1.3

Copper (DTPA) mg/kg

2.1 1.9 2.1 2.1 1.8 2.0 1.9 2.0 1.9

Iron (DTPA) mg/kg

330.0 336.7 353.3 326.7 350.0 356.7 346.7 333.3 386.7

Manganese (DTPA) mg/kg

49.3 32.0 22.3 46.7 29.3 23.0 57.0 30.0 23.3

Zinc (DTPA) mg/kg

7.6 8.1 5.0 8.2 6.0 8.4 7.4 5.3 5.3

Sulfate Sulfur (KCl40) mg/kg

18.0 43.7 18.3 16.0 24.7 18.7 20.0 16.0 27.7

Organic Carbon (OC) %

3.8 4.9 4.5 4.2 4.7 4.6 4.2 4.7 5.4

Aluminium (KCl) mg/kg

27.7 15.0 31.7 12.0 36.3 20.0

Calcium (Amm-acet.) %

59.0 72.0 70.0 60.0 70.3 72.7 62.3 68.0 71.0

Magnesium (Amm-acet.) %

30.0

22.3

24.7

30.3

23.3

22.3

27.0

26.3

24.3

Potassium(Amm-acet %

5.9

3.8

3.4

4.8

4.5

3.3

4.5

3.9

3.6

Potassium to Magnesium Ratio

0.2

0.2

0.1

0.2

0.2

0.1

0.2

0.1

0.2

Variation in productivity/profitability with time & management influence

wgcma-soil-ph-graph1

Reporting

How results have been reported (e.g. leaflet, technical report, journal article)

Field day, Newsletter, Gippsland Soil Trial directory ,
Communication and extension. Reports on the findings after each milking season will be prepared and a full project report generated at the end of the third year.
A workshop to present and discuss results with interested farmers, advisers and agency staff.

Level of review of results

Best Available Science (BAS) score by Craig Clifton (SKM) 2011 prior to commencement.
BAS score revision during trial -Tony Gardner WGCMA

Miscellaneous

Intellectual property ownership

MDF, WGCMA

Approval to publish project summary in trial directory

Yes

Other comments

Application of N to the trial plots was not undertaken for two harvests due to staff turnover. This oversight has now been rectified and N applications to the plots has been restored.

Harvest 6 was interrupted by an extreme rain event and grazing of the subject paddock was not within the normal management boundaries.