Soil physical properties of dairy farms in Southeastern Australia

Leading Organisers and Collaborators:

Department of Environment and Primary Industries (DEPI)
Future Farming Systems Research Division.

Contact:

MA Rab, K Greenwood,
SR Aarons, M Hannah

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Project details

Objectives:

(i) To quantify the variability in soil physical properties; and

(ii) To develop a sampling strategy for future monitoring of Victorian dairy soils.

 

Basis:

Dairy farm management practices associated with animal treading can have detrimental impacts on physical and hydrological properties of soils. The major impacts are soil pugging and compaction (see Figs 1 and 2). Soil compaction is very important because it strongly influences water infiltration rates, hydraulic conductivity and root growth. Reduced infiltration rates can lead to increased erosion and deterioration in water quality, whilst reduced root growth can retard pasture growth. Soil bulk density, porosity and water holding capacity are the most important soil physical properties which affect the establishment of pasture seedlings and pasture growth.

Farm details

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Summary of Key Findings:

• Most of the farms had macroporosity values less than 15%, suggesting that root growth may be moderately to severely affected due to low oxygen availability in the 0-10 cm depth.

• For most soil properties, the variances between sampling points within a site were highest, followed by between farms.

• These finding have implications for developing a sampling strategy for monitoring dairy soils.

Results:

• Macroporosity was found to be the most variable soil property (Table 1) in the South West Victorian dairy farms.

• Significant (P < 0.01) differences between the 24 farms were observed for all soil properties. Differences in soil properties between soil types were also found to be significant (P<0.01) except for macroporosity and field capacity.

• Variance component analysis (Table 2) showed, that for most of the soil properties, variances between sampling points within a site (σ2 S ) were the highest, followed by between farms (σ2 F ) , between paddocks within a farm (σ2 P ) , and between sites within a paddock (σ2 L ).

• Mean values of bulk density and macroporosity for the 24 farms varied from 0.76 – 1.4 Mg/m3 and 5.5 – 21.5 vol% respectively. The majority of the farms had macroporosity values less than 15% (Fig. 4).

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Methods and Measures

Soil physical data were collected from 24 dairy farms in South West Victoria (Fig. 3).

• Three paddocks in different landscape positions (generally high, mid and low points within the local topography) were selected on each farm, giving 72 paddocks.

• Two to 3 sampling sites (10 m by 10 m) per paddock were selected to represent different topographic and/or animal use zones,

• Three undisturbed intact soil samples were collected from the 0-10 cm depth from these sites (total of 561 samples).

• Soil water contents of the undisturbed samples were determined at −10 kPa (field capacity) using a tension table ceramic suction plate apparatus.

• Soil bulk density and total porosity were determined using a standard method (see Rab et al. 2011).

• Macroporosity was determined as the difference between total porosity and field capacity

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