OPTIMISING INOCULATION TO IMPROVE LEGUME PERFORMANCE

Recognising that Rhizobia are living organisms which are highly sensitive to pH, heat and desiccation, is important in managing the success of inoculation. Rhizobia are highly host specific, hence the importance of matching the correct strain and group of Rhizobia with the legume species that is to be inoculated. Once Rhizobia contact root hair, they infect the root hair and multiply within the infection site to form a nodule.

Industry best practice is still sowing peat inoculated legumes within a day of treating, although successful nodulation relies upon survival of Rhizobia which is influenced by soil moisture or follow up rainfall.

If peat is not being used, granular inoculants are generally preferred over freeze dried, as they are not as sensitive to contaminants or fungicide on the seed, or as time critical to sow, but granules can damage equipment being used.

The Rhizobia count of granules vary significantly, hence different rates are required depending on the manufacturer as well as the row spacing, where calculation of the rate per seed furrow is required. Dual strain products are often successful because of their higher rates of inoculum counts, rather than an additive effect of two strains.

Dry sowing trials have concluded that doubling the rate of peat applied, is only marginally more successful than single rate applications. Where there is no follow-up rain within a week, there is generally no significant difference in the inoculation result between application rates. Granular inoculants are recommended under dry sowing conditions, because of their ability to survive for longer periods without moisture.