Main authors: Abdallah Alaoui
Editor: Jane Brandt
Source document: Alaoui, A. (2018) Visual Soil Quality Assessment Manual v2: assessment of soil and plant quality for the season 2018.  iSQAPER Report  49 pp

 

Importance

Poor soil aeration, high levels of soil saturation and high mechanical resistance to root development due to soil structure degradation can increase root-rot and soil borne pathogens. They can also reduce the ability of root systems to overcome the harmful effects of pathogens resident in the topsoil. Plant diseases encouraged by degradation of soil structure include fusarium, pythium, phytophthoria, rhizoctonia, and vesicular-arbuscular mycorrhizal fungi (Department for Environment Food and Rural Affairs, Defra).

Assessment

To carry out an assessment of root diseases you will need:

  1. a small spade and bucket to place the plants in
  2. a bucket of water for washing out the root systems
  3. additional clean water for final examination
  4. a flat white tray containing water to be used for identifying and assessing root diseases
  5. a magnifying glass.

In order to assess/diagnose plant diseases, the following methods are used.

  1. Carefully dig up 3 plants along the crop monitoring path, making sure that soil is left intact around the root system of the plant.
  2. For cereal root diseases, rate the severity of root disease identified (see figures below). For other diseases, indicate whether or not they are present in the crop.
  3. At each collection point, visually assess the area of crop affected by the disease.
  4. Calculate an average area affected for the 10 sites observed.

Interpreting root disease assessment

Ratings of 1 or 2 for cereal root diseases indicate that an economic yield loss is occurring. It will be necessary to review your agronomic management, in particular your selection of crop species and variety when planning future crop rotations.

Scoring

Scoring should be made using Figures 16 – 18 and related Tables 4 – 6.

The final score should be the one indicating the least good condition. If one score (among the scores given in tables 4 to 6) indicates poor condition, poor condition should be reported. You should score moderate conditions if the worse score among all score is moderate. You should score good conditions only when all scores are good.

 

VSA2 fig16
Cereal cyst nematode
VSA2 fig17
Rhizoctonia root rot
VSA2 fig18
Take-all


Table 4. Scoring of the cyst nematode assessment

Cereal cyst nematode Score  
Root length normal 0
Roots are 40 % shorter than healthy roots 1
Roots are 60 % or more shorter than healthy roots 2

Table 5. Scoring of the Rhizoctonia root rot assessment

Rhizoctonia Score 
No roots are shortened 0
Up to 25% of the roots are shortened 1
More than 25% of roots are shortened 2

Table 6. Scoring of the Take-all assessment

Take-all Score 
No lesion visible 0
1 or 2 main seedling roots have lesions 1
3 or more seedling roots have lesions 2

 


References

Department of Primary Industries and Regional Development. https://www.agric.wa.gov.au/mycrop/monitoring-root-disease.

Department for Environment Food and Rural Affairs, defra. http://adlib.everysite.co.uk/adlib/defra/content.aspx?doc=202989&id=203609

 

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