A recent GRDC funded study on dry sowing pulses into acidic soils has shown that nodulation is greatly improved when the inoculation rate is doubled. The study by SARDI has also shown that the increased rate provides better nodulation in pulse species into a new paddock where they haven’t been grown before.
However, if you are getting poor nodulation in acidic soils, you shouldn’t be blaming the rhizobia. Most pulse crops and their associated rhizobia are sensitive to low pH. If low pH is not corrected poor nodulation may continue to result, even when good inoculation practices have been followed. The plant and the rhizobia both need each other for the process to work to its best. The plant is the source of carbon for the rhizobia, and the rhizobia are the source of nitrogen for the plant. Once the nodules have formed, the amount of nitrogen fixed is driven by the plant’s growth rate and its demand for nitrogen. If there are soil constraints, this process can’t work as well, and there is a lower nitrogen demand for the struggling plant.
The only downside with doubling your rate of inoculant is that some growers have experienced seeder blockages. Therefore we suggest testing a small batch of seed first to avoid the issue on a larger scale.
During these studies, SARDI has also been working on a new strain of rhizobia, which it appears will have a substantial impact in areas with higher rainfall and low pH soils. This new strain will most likely be available in 2021. If you are finding problems with acidic soil, it is important to make sure you are soil testing and applying lime where it’s needed to fix these issues.
We still have stock of Faba Bean, Pea, Lentil, Chickpea & Lupin peat inoculant in stock, so come see us today and ask any questions you may have.