Grains Research and Development

Date: 14.04.2016

Crop history key to legume inoculation

Author: Rebecca Barr

Liz Farquharson

Dr Liz Farquharson suggests growers follow the GRDC Back-Pocket Guide for the best response to legume inoculation.

New GRDC-funded research by the South Australian Research and Development Institute (SARDI) has confirmed that field peas are unlikely to respond to inoculation, unless they are grown on acidic soils or where there is no recent history of the crop.

SARDI soil biologist Dr Liz Farquharson says the study found Rhizobium inoculation did not cause a grain yield response in field pea grown on soils where there was a history of growing the crop and neutral to alkaline pH.

“This was despite evidence of positive effects of inoculation on nodule mass and grain nitrogen content. On these soils, it would appear that the rhizobia in the soil are not limiting the yield of field pea. Nodulation and N2-fixation did not always meet our expectations, suggesting factors other than the rhizobia might be limiting to the symbiosis.” she said.

Field pea, faba bean and lentils are all inoculated by the same rhizobia, so a history of any of the three crops is likely to indicate there is adequate rhizobia in the soil.

“We are reluctant to discount the possibility of a response in faba bean from inoculation at this stage, as it produces more biomass, however we anticipate the response in lentils would be the same as field pea,” Dr Farquharson said.

The GRDC Back Pocket Guide advises that the likelihood of crop response to inoculation is:

  • High if there is no history of pea, vetch, bean or lentil crops, or soils with pH (CaCl2) below 6.0 and high summer temperatures (over 35oC for 40 days).
  • Moderate if there was a previously inoculated pea, vetch, bean or lentil crop more than four years ago, or a recent crop which nodulated poorly and performed below expectation.
  • Low in loam or clay soils with neutral to alkaline pH, and a recent well-nodulated host crop.

SARDI is a division of Primary Industries and Regions SA.

More Information

Liz Farquharson, 08 8303 9452, liz.drew@sa.gov.au

Useful Resources

GRDC Project Code DAS00128

Region South