Monitoring pulse nodulation

All pulse plants require healthy root systems in order to maximise growth and yield. Healthy nodulation of pulse roots is particularly important if plants are to maximise nitrogen fixation and therefore plant growth. Healthy nodules need to be present on both the taproot and lateral roots. A healthy nitrogen fixing nodule is pink inside. Grey or green nodules do not fix nitrogen.

Inspecting lupin roots

How to assess pulse nodulation

The following procedure should be used in order to assess the degree of nodulation found on pulse plants;

  1. Assess crop nodulation 10 – 12 weeks after sowing
  2. Carefully dig 10 plants at random across the area to be assessed, keeping the soil intact around the root ball of the plant
  3. Very carefully wash dirt off plant roots in a bucket of water
  4. Rinse the root systems and observe the nodules found on the root system (observing the size, number and colour of the nodules)
  5. Score the root system, using the diagram below
Pulse root nodulation ratings
Pulse root nodulation ratings

Interpreting pulse nodulation assessment

Poor nodulation may be due to a number of agronomic factors which should be explored. The reasons why rhizobium does not thrive may be due to any number of reasons including:

  1. Poor environmental conditions (cold temperatures, moisture stress) during emergence and growth of the crop
  2. Soil pH may not suit the survival of the particular rhizobia for the crop
  3. Poor establishment of soil rhizobia by previous crops grown in the paddock
  4. Poor inoculation
  5. Fertiliser practices
  6. Root diseases like Rhizoctonia


Page last updated: Thursday, 15 January 2015 - 9:47am