Nutrition management

Nodulation failure

Healthy nodulation showing active signs of nitrogen fixation (pink colouring). View full sized image
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Healthy nodulation showing active signs of nitrogen fixation (pink colouring).

Healthy nodulation showing active signs of nitrogen fixation (pink colouring).

Signs of nodulation failure are plants that become yellow or pale green with restricted growth, especially during cold wet periods through the seedling stages. Oldest leaves are worst affected.

There are none or few nodules on roots, or nodules lack red pigmentation inside.

 

Nodule score

Distribution and number of effective nodules

Crown/Tap root

Laterals

0

0

0

0.5

0

1-4

1

0

5-9

1.5

0

10 or more

2

Few

0

2.5

Few

Few

3

Many

0

4

Many

Few

5

Many

Many

Apply nitrogen needs of affected crops with N fertiliser if economic. Ensure future crops are adequately covered with viable Group F inoculum.

Plants can appear normal until flowering on soils with moderate to high nitrogen levels, but then become pale green, with older leaves being affected most and first.

Professor J Howieson, Centre for Rhizobium Studies & National Rhizobium Program, GRDC