Nitrogen (N) fixed by rhizobia has a huge benefit in the rotation for subsequent crops. So inoculating pulses correctly and ensuring adequate nodulation occurs can be very important. Factors that can affect rhizobia survival and consequently how well the inoculating process worked are typically environmental stresses such as heat, toxic chemicals and acidic conditions.
In the North Central region of Victoria pulses are being grown on paddocks where they haven’t generally been grown before meaning suitable rhizobia may not be present in the soil.
BCG are working on a demonstration trial funded by the GRDC and Mallee Sustainable Farming through the ‘Increasing the effectiveness of nitrogen fixation in pulse crops through extension and communication of improved inoculation and crop management practise in the southern region’ project.
The trial is located in Pyramid Hill and has been designed to compare and highlight the effect of new and old rhizobia strains and different application rates on the nodulation of field peas and the subsequent impact on crop biomass, grain yield and grain quality in acidic soil conditions.
BCG are preparing to do nodulation assessments on this trial in a few weeks as the ideal time is towards the end of winter and early spring. Which is the same time that growers should be getting out in the paddock and checking how the nodulation is going in pulses that they inoculated. Similarly, growers should be assessing paddocks they may have left the seed bare knowing there had been history of rhizobia in those paddocks. It’s a good idea to monitor and confirm if the inoculation process was a success but it’s also just as important to have a look at those paddocks that weren’t inoculated to see if adequate nodules have formed or not and if maybe next time you should consider inoculating the seed to optimise nodulation. Checking nodulation is a fairly straightforward process. It involves collecting a sample of plants from different locations across your paddock, carefully washing the roots and examining the nodules attached to the roots. Cut some nodules in half and check if they are pink to ensure the nodules are actively fixing N. A great resource with detailed instructions on this process and a rating system for the number of nodules can be found here: https://grdc.com.au/tt-legume-n-fixation
