- Soil health is a measure of the sustainability of farming practices on soil
- Standard soil chemical tests are often undertaken to determine nutrient levels but these provide very limited information on soil biology and physical properties
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- The use of relatively simple assessments of soil health can enhance our understanding of the physical, chemical and biological status of the soil
- The Visual Soil Assessment (VSA) is the preferred method for advisors and land holders to assess the condition of soils is the field in southern Victoria
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Understanding the question
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| Why undertake a soil health assessment?
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- The maintenance of good soil health is vital for the environmental and economic sustainability of agricultural activities in the region.
- A decline in soil health has a marked impact on plant growth and yield, grain quality, production costs and the increased risk of soil erosion.
- A decline in soil physical properties in particular takes considerable time and cost to correct. Safeguarding soil resources for future generations and minimizing the ecological footprint of annual cropping are important tasks for land managers.
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- Often, not enough attention is given to:
- the basic role of soil health in efficient and sustained production
- the effect of the condition of the soil on the gross profit margin
- the long-term planning needed to sustain good soil health
- the effect of land management decisions on soil health
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| What is a soil health assessment?
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- A soil health assessment kit is a collection of selected field procedures to evaluate the physical,
chemical, and biological properties of the soil. Physical properties assessed by the kits generally include bulk
density, water content, infiltration rate, aggregate stability, slaking, and morphological estimations.
Biological properties measured include soil respiration and earthworms. Soil chemical properties measured include pH, electrical conductivity (EC), and soil nitrate levels.
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- The tests, or indicators, are designed as a screening tool to provide immediate results for comparing management systems, monitoring changes in soil health over time, and for diagnosing possible soil health problems due to land use and management.
- All kits include a guide that provides a list of supplies and instructions for conducting the on-farm tests, and interpretive information for each test.
- These tests can be easily conducted on the farm by trained field personnel or by landowners themselves to assess the health of their soil.
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| Undertaking your own soil health assessments
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How can you achieve this?
There are a number of these tests that can be used by farmers. Two methods are described here:
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1. NZ Visual Soil Assessment (VSA)
See the Visual Soil Assessment at: http://www.bioagrinomics.com/visual-soil-assessment.html
The Visual Soil Assessment is a quick, simple and effective method to assess soil quality and plant performance. It is being assessed by DPI Victoria as the preferred method for advisors and land holders to assess the condition of soils is the field in southern Victoria.
How it works:
- VSA is based on the visual scoring of key physical indicators of soil quality, and incorporated on an easy to use scorecard. The soil is scored by comparing the key indicators with three diagnostic photographs showing an example of good, moderate and poor condition (see figure 1). The soil indicators are supported by plant 'performance' indicators that link soil condition to pasture/crop production.
- The plant performance scorecard allows the plant to have its say as to what it thinks about the soil it is growing in. Plant scores will normally follow the soil score but if the two differ, the reason is usually because of the weather or farm management practices.
- Placing the spotlight on farm management practices is what the VSA is all about. The indicators are underpinned by extensive research in New Zealand and are linked to economic performance.
- Soil indicators are generic and have the major advantage of being largely independent of soil type. That is, while soil type can influence the VSA score, the interpretation of what you see is largely independent of soil type.
Figure 1: Visual scoring (VS) of soil structure under pasture � Source: Shepherd,G. (2000)
[View larger image]
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The NZ VSA tool kit
The VSA tool kit comprises of:
- a spade � to dig a soil pit and to take a 200-mm cube of soil for the drop shatter soil structure test
- a plastic basin (about 450 mm long x 350 mm wide x 250 mm deep) � to contain the soil during the drop shatter test
- a hard square board (about 260x260x20 mm) � to fit in the bottom of the plastic basin on to which the soil cube is dropped for the shatter test
- a heavy-duty plastic bag (about 750x 500 mm) � on which to spread the soil, after the drop shatter test has been carried out
- a knife (preferably 200 mm long) to investigate the soil pit and potential rooting depth
- a water bottle � to assess the field soil textural class
- a tape measure � to measure the potential rooting depth
- a VSA field guide � to make the photographic comparisons
- a pad of scorecards � to record the VS for each indicator
When it should the VSA be carried out � �Worm test�
The test should be carried out when the soils are moist and suitable for cultivation. If you are not sure, apply the �worm test�. Roll a worm of soil on the palm of one hand with the fingers of the other until it is 50 mm long and 4 mm thick. If the soil cracks before the worm is made, or if you cannot form a worm (for example, if the soil is sandy), the soil is suitable for testing. If you can make the worm, the soil is too wet to test.
- Soil structure
- Earthworm numbers
- Soil smell
- Potential rooting depth
- Surface ponding
- Surface crusting
- Soil erosion potential
- Pasture quality
Examples of pasture indicators include an assessment of:
- Pasture quality
- Clover nodules
- Pasture colour, growth and urine patches
- Root length and root density
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2. Northern Rivers Soil Health Card
10 simple soil tests that you can undertake yourself
See the Northern Rivers Soil Health Card - A soil management tool developed by
farmers for farmers
- The soil health card lists 10 straightforward visual soil tests that require simple
equipment and can be carried out by one person in the field. It provides space for you to
rate your own soils after carrying out the tests
- By testing regularly and keeping the cards, you can build up a record of your soil health,
and understand the effect of management practices on soil health
The 10 recommended tests are:
1. Ground cover
- using a wire frame quadrant made from a coat hanger
- both ground plants and mulch contribute organic matter to the soil that will feed
soil animals and microbes
- roots of ground plants also help maintain good soil structure
2. Penetrometer
- Push a homemade penetrometer made from 10 gauge high tensile wire into the
soil as deep as you can with modest effort
- The easier it is to penetrate the soil, the better the deep root development and
water infiltration
3. Infiltrometer
- measures the rate at which a fixed volume of water soaks into the soil using cut
PVC pipe bevelled at one end to push into soil
- a higher rate of infiltration will mean your soil will absorb rainfall more quickly,
resulting in less run off and erosion
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4. Diversity of soil life
- number and variety of soil animals (using wire quadrant)
5. Root development
- 20cm square and deep hole cut out of soil
- examine roots
- distribution of fine roots will show whether soil structure is restricting the plants�
access to nutrients
6. Soil structure
- examine the size and arrangement of the soil aggregates or �crumbs� from block
of soil cut for root development test (above)
- poor structure may be seen either as overly solid soil (hard crumbs, soil layers or
clods) or as very loose soil (absence of even small crumbs, as for example in
beach sand)
- good structure results in easy passage of air and water, an ability to hold water
and superior resistance to erosion
7. Aggregate stability
- select three or four pea-sized soil aggregates from about 10 cm depth
- drop the aggregates into 125 ml water in the small wide mouthed jar and allow to
stand for one minute
- observe if the aggregates break apart or stay intact
- poor aggregate stability is associated with greater susceptibility to erosion
- repeat the test with a sample from a depth of 20 cm
8. Earthworms
- break up your entire soil block into crumbs and count earthworms > 25mm
- higher numbers of earthworms indicate conditions that are favourable (more
organic matter, high pH, low chemical residues)
- mostly these are also conditions favourable for plant growth
9. Soil pH
- take two small samples of soil from the side of the hole, one from 5 cm and one
from 20 cm depth
- test each sample for pH
- acidity has a strong effect on the ability of plants to take up soil nutrients as well
as upon the wellbeing of soil organisms
10. Leaf colour
- examining your crop, trees or pasture at the soil test site may reveal plant health
problems not identified by the completed soil tests
- in crops examine fully formed leaves about four leaves back from the growth tip
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Soil health assessments in the Corangamite region:
Both the NZ VSA and Northern Rivers Soil Health cards were trialled by the Heytesbury Soil Health project in south west Victoria in 2006-07 (Greenwood et al 2008). The VSA was well received by landholders as they were easily able to compare in-field conditions with the pictures in the guide. However, it was suggested that scoring of soil health has the potential to be controversial and contentious for individual farmers and the industry when scores are low (or poor) compared with benchmarks and scores were often not reflected by traditional quantitative soil chemical and physical data.
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Other soil testing that you can undertake:
- Examining your soil and assessing its condition enables you to make better
decisions on the use of your paddocks, and protects your investment in the soil
- You will be able to make informed decisions on tillage, crop and pasture
selection
- In the longer term, your whole-farm plan will reflect the changes in soil type
across your property, making each paddock more uniform so it is easier to
manage
- Soil properties are of two types: those that can be seen by visual
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Other related questions in the Brown Book
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Brown Book content has been based on published information listed in the Resources and References sections below
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- Tools and systems for assessing soil health. Victorian Resources Online - Department
of Environment and Primary Industries, Victoria.
- Why test your soil? -. Soil Health Knowledge Bank.
- Northern Rivers Soil Health Card - A soil management tool developed by farmers for farmers.
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- Shepherd, T.G.; Ross, C.W.; Basher, L.R.; Saggar, S. (2000) Visual soil assessment, Volume 2.- Soil management guidelines for cropping and pastoral grazing on flat to rolling country. horizons. MW & Landcare Research, Palmerston North.
- Greenwood,K., Rees,D., Davey,M. and Brown,A.(2008) - Final report to Dairy Australia on DAV 12222, HDLN Soil and Water Dairy Action Program - Soil Assessment Component Department of Primary Industries, Victoria.
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