Wednesday 17 June 2015

Visual Soil Assessment – A practical guide to assessing your soil quality

The Visual Soil Assessment (VSA) was developed by Landcare Research to give cropping and pastoral farmers respectively a straight forward and time efficient checklist to use in the field to assess the state of their soil, primarily physical soil quality.

The VSA can be found online at:

The soil’s physical properties are vital to the ecological and economic sustainability of land. They control the movement of water and air through the soil, and the ease with which roots penetrate the soil. Damage to the soil can change these properties and reduce plant growth, regardless of nutrient status. Decline in soil physical properties takes considerable expense and many years to correct, and can increase the risk of soil erosion by water or wind.
The primary functions of the soil are to provide plants with air, water, nutrients and a rooting medium for growth and physical support (image sourced from the Landcare Research website) 
The VSA aims to help farmers identify changes occurring to soil physical properties so that they can assess the effect that these changes will have on their soil quality and as a result the sustainability of their land management and long term profit.
Pictures in the VSA guide can be helpful when carrying out the assessment in the field (image sourced from: VSA Volume 1).
 The assessment can be carried out quickly, reliably and cheaply with little equipment, training or technical skills. The scorecard below is to record those visual soil indicators used to assess soil quality. There is a similar scorecard for recording plant indicators. You are then able to compare the two sets of indicators to see if you have similar scores for both and if not why. For instance, is damage to soil quality not being seen in crops yet or are crops struggling to recover from previous soil damage?

VSA Scorecard (image sourced from: VSA Volume 1).
Below each indicator is a section in the online VSA booklet to refer to for assistance. Pictures are included so you are able to compare what you are viewing with examples. You will need basic equipment such as a spade, the score card, a surface to drop soil onto for a shatter test and a bin to contain soil. Each indicator is given a weighting and at the bottom of the scorecard you add the scores for the various indicators. Values falling within certain ranges are deemed “poor, moderate and good” quality. If your quality is poor or moderate it is suggested that you refer to Volume 2, also easily accessible from Landcare Research online. This volume contains tips on how to improve your soil quality or maintain it if it is already good.

Tips include:
  • Cultivating at the correct moisture levels to avoid smearing of soil, formation of cultivation pans and reduced infiltration when the soils are too wet. 
    (image sourced from: VSA Volume 2)
  • Use a subsoiler to break cultivation pans and increase root growth
  • Maintain soil organic matter levels to ensure porosity, drainage and root growth.
    (image sourced from: VSA Volume 2)
By utilising these resources you will gain a better appreciation for the state of your soil and will be able to identify when changes are occurring and why. The VSA is a simple tool and when used regularly will help with building a picture of soil quality. There are a range of other resources that can continue on from the VSA, further your knowledge of your soil and assist with management. SINDI, another resource for determining soil quality, will be discussed in a future blog post along with hands on ways to identify your soil type and S-Map, how its geomorphological (land formation) history of soils can be used to assist your farming.

The informative blog post you have just read was written by Nicole Mesman - BSc (Hons) Soil Science.